Medical Encyclopedia C: Medical Terms Explained

Caecum

The first part of the large intestine with the worm-like appendix, whose inflammation is commonly called appendicitis.

Care directive (guardianship preference)

A written advance document in which a person specifies whom the guardianship court should appoint as legal guardian if they can no longer manage their own affairs. It can also contain wishes about how the guardianship is carried out.

Care needs assessment tool (Germany)

The procedure used by the Medical Service since 2017 to determine the need for long-term care in Germany. It assesses independence in six modules and results in the care level.

Carotid artery

The neck artery running on each side of the neck, dividing into a branch for the brain and one for the face and neck. Narrowing here is an important cause of stroke.

Central retinal artery

A branch of the ophthalmic artery that runs in the optic nerve to the eye and supplies the inner retinal layers. Its occlusion causes sudden, painless blindness in one eye and is an emergency with increased stroke risk.

Cerebral aqueduct

A narrow channel in the midbrain connecting the third and fourth ventricles. Narrowing obstructs cerebrospinal fluid flow and can cause hydrocephalus.

Chest compress

A moist or warm wrap around the chest traditionally used for coughs and colds to promote relaxation. Robust evidence of effectiveness is lacking; in infants caution is needed because of overheating.

Chest pain

Pain in the chest with many possible causes, from muscle tension to heart attack. Pressing pain with breathlessness or cold sweat is an emergency.

Chorioamnionitis

Infection of the amniotic fluid, membranes and placenta, usually from ascending bacteria after the waters break. Signs are fever, a fast pulse in mother and baby and a tender uterus; antibiotics and prompt delivery are needed.

Choroid

The vascular middle layer of the eye between the retina and the sclera, supplying the outer layers of the retina. It is part of the uvea.

Choroidal melanoma

The most common malignant eye tumour in adults, arising from pigment cells of the choroid. It often goes unnoticed for a long time and is usually treated with radiation; metastases typically form in the liver.

Choroidal naevus

A benign pigmented spot in the choroid of the eye, noticed during fundus examination. Regular checks aim to detect a rare transformation into melanoma early.

Chronic exertional compartment syndrome

A temporary rise in pressure in a muscle compartment, usually in the lower leg, during sporting activity. It causes tension pain, numbness or weakness that subsides at rest.

Circum-rescue collapse

Sudden cardiac arrest in severely hypothermic people during or shortly after rescue. It is caused by movement and changes of position that bring cold blood to the heart, which is why rescuers handle casualties gently and keep them lying flat.

Circumflex scapular artery

A branch of the subscapular artery that passes through the triangular space to the back of the shoulder blade. It supplies the scapular flap, a commonly used skin flap.

Clinical block placement

A compulsory clinical placement of several weeks during the clinical phase of medical school, in which students learn directly with patients in one specialty.

Co-payment limit (Germany)

The ceiling on co-payments in German statutory health insurance: if they exceed two per cent of annual gross household income in a year, or one per cent for people with serious chronic illness, the insured can be exempted.

Coarctation of the aorta

A congenital narrowing of the main artery beyond the vessels to the arms. Typically blood pressure is higher in the arms than in the legs; it is treated surgically or by catheter.

Comfrey

A medicinal plant whose root is used externally in ointments for bruises, strains and sprains. It must not be taken internally because of liver-damaging constituents.

Common hepatic artery

A branch of the coeliac trunk running to the liver and dividing into the proper hepatic artery and the gastroduodenal artery. Its position is crucial in pancreatic and liver surgery.

Common iliac artery

The artery formed at the level of the fourth lumbar vertebra by the division of the abdominal aorta. It divides into the internal and external iliac arteries.

Common interosseous artery

A short trunk from the ulnar artery that divides into the anterior and posterior interosseous arteries and supplies the deep forearm muscles.

Complementary feeding

Purées and solid foods introduced in addition to milk from around the fifth to seventh month.

Computer glasses

Glasses specifically adjusted to the distance from the screen that make computer work easier in presbyopia.

Conditional marketing authorisation

A provisional European approval of a medicine for an unmet need although not all data are yet available. It is valid for one year at a time and obliges the manufacturer to provide further studies.

Congenital adrenal hyperplasia

A group of inherited disorders of cortisol production in the adrenal cortex, usually due to 21-hydroxylase deficiency. Androgen production increases, causing virilisation of the external genitalia in girls and sometimes life-threatening salt loss; newborn screening detects the condition.

Congenital heart defect

A malformation of the heart or nearby vessels that affects about one per cent of newborns, for example a hole in the heart’s septum.

Conjunctiva

A thin, transparent mucous membrane covering the inside of the eyelids and the white of the eye. It protects the eye and helps spread the tear film.

Connective tissue

Tissue that supports, connects and surrounds organs. It consists of cells and fibres such as collagen and elastin.

Connective tissue graft

Transplantation of connective tissue, usually from the palate, to cover exposed tooth necks or thicken the gum. As with any procedure, pain and wound healing problems at the donor site are possible.

Connective tissue weakness

A predisposition to less firm connective tissue that can favour stretch marks, cellulite, varicose veins or hernias. It is often partly hereditary.

Contraceptive pill

Oral hormonal contraceptive that mainly prevents ovulation. A rare risk is thrombosis.

Controlled drug documentation

The legally required, complete recording of receipt, use and stock of controlled drugs such as opioids in practices, hospitals or care facilities. It is inspected regularly and must be kept for several years.

Controlled drugs (narcotics)

Legally specially regulated substances with addictive potential, such as strong opioids. In Germany prescription, storage and documentation are governed by the Narcotics Act, using a special prescription form.

Counselling for relatives

Information, training and support for family members of people needing care or seriously ill people, for example on care techniques, support services and respite. It helps prevent carers becoming overwhelmed.

Cystic artery

The gallbladder artery, usually a branch of the right hepatic artery, running in Calot’s triangle to the gallbladder. During gallbladder removal it must be clearly identified and closed.

Cystitis

Inflammation of the urinary bladder, usually caused by bacteria. Burning on urination and frequent urge to urinate are typical; women are affected more often because of their shorter urethra.

In depth: Cystitis →

c-ANCA

Pattern of antineutrophil cytoplasmic antibodies with granular staining of the cytoplasm, usually directed against proteinase 3. It is typical of granulomatosis with polyangiitis.

C-peptide

Fragment released in equal amounts when insulin is formed. Measuring it shows how much insulin the pancreas is still producing itself.

C-reactive protein (CRP)

Blood marker of inflammation produced by the liver in increased amounts during inflammation and infection. Very high levels point more towards a bacterial infection.

C1 esterase inhibitor

Blood protein that restrains the complement and kallikrein-kinin systems. Deficiency or dysfunction leads to hereditary angioedema; as a concentrate it is also used to treat attacks.

C3 glomerulopathy

Rare kidney disease in which, due to dysregulation of the complement system, complement factor C3 is deposited in the glomeruli. It leads to protein and blood in the urine and can progress to kidney failure.

CA 125

Tumour marker used mainly to monitor ovarian cancer. It is unsuitable for screening because it can also be raised in endometriosis, menstruation or ascites.

CA 15-3

Tumour marker measured mainly to monitor metastatic breast cancer. It is not suitable for screening because it can also be raised in benign conditions.

CA 19-9

Tumour marker used mainly to monitor the course of pancreatic and bile duct cancer. It is also raised in bile duct obstruction, and some people cannot produce it for genetic reasons.

CA 72-4

Tumour marker that can be raised in stomach and ovarian cancer. It is not suitable for screening, at most for monitoring the course.

Cabazitaxel

Taxane given by infusion in metastatic prostate cancer when the disease has progressed on docetaxel. Because severe neutropenia is common, a growth factor is often given preventively.

Cabergoline

Long-acting dopamine agonist that strongly inhibits prolactin production by the pituitary gland. It is the drug of choice for prolactinomas and is also used to stop lactation; with high doses over long periods, the heart valves are monitored.

Cabot rings

Ring- or loop-shaped inclusions in red blood cells thought to be remnants of the mitotic spindle. They occur rarely in severe megaloblastic anaemia or lead poisoning.

Cabotegravir

HIV integrase inhibitor that can be given as a long-acting injection every one to two months, either for treatment (together with rilpivirine) or for prevention (PrEP).

Cabozantinib

Oral multikinase inhibitor that blocks MET, VEGFR and AXL, among others, and is used in renal cell, hepatocellular and thyroid cancers. Diarrhoea, hand-foot syndrome and high blood pressure are common.

CAD/CAM dental restorations

Dental prostheses designed on a computer and milled from a block of material or printed by machine. They are often based on a digital impression taken with an intraoral scanner.

CADASIL

Inherited disease of the small blood vessels of the brain caused by changes in the NOTCH3 gene. Typical features are migraine with aura, repeated small strokes from middle age and later dementia.

Caeruloplasmin

Copper-transporting blood protein produced in the liver. A low level is an important clue to Wilson’s disease.

Café-au-lait spot

Sharply defined, light brown skin patch that is common and harmless on its own. Six or more larger spots may indicate neurofibromatosis type 1.

Cafedrine

Circulatory drug used in a fixed combination with theodrenaline mainly for low blood pressure during anaesthesia. It increases cardiac output and blood pressure without raising the pulse much.

Caffey disease

Infantile cortical hyperostosis, a rare disease of young infants with painful soft tissue swelling, fever and new bone formation, often in the lower jaw. It usually resolves on its own over months.

CAGE questionnaire

Short questionnaire with four questions about alcohol use, for example about the wish to cut down. Two or more “yes” answers suggest an alcohol problem.

Cagrilintide

Long-acting analogue of the hormone amylin that promotes satiety and slows gastric emptying. It is being studied mainly in combination with semaglutide for weight reduction.

Cairo classification

Classification of gum recession into three types according to attachment loss at the adjacent tooth surfaces. It helps predict whether complete root coverage is possible.

Calcidiol

25-hydroxyvitamin D, the storage form of vitamin D made in the liver. Its blood level is the best measure of vitamin D status; the active form is produced only in the kidney.

Calcifediol

25-hydroxyvitamin D3, the first metabolic stage of vitamin D in the liver. As a medicine it raises vitamin D levels faster than colecalciferol; because of the risk of overdose with hypercalcaemia, medical monitoring is advisable.

Calcinosis cutis

Deposition of calcium salts in the skin, showing as hard, whitish nodules. It occurs, for example, in systemic sclerosis, dermatomyositis or disorders of calcium-phosphate balance.

Calciphylaxis

Rare, severe calcification of small skin blood vessels, usually in dialysis patients, leading to very painful areas of dying skin. It carries a high mortality and requires interdisciplinary treatment.

Calcipotriol

Vitamin D derivative in ointments and foams that slows the excessive skin renewal in psoriasis. It is often combined with a corticosteroid.

Calcitonin

Hormone produced by special cells of the thyroid gland that can slightly lower calcium levels. In medicine it is used mainly as a tumour marker for medullary thyroid cancer.

Calcitriol

Active form of vitamin D produced in the kidney that promotes calcium absorption in the gut. It is often lacking in kidney failure.

Calcium

Mineral that builds bones and teeth and is needed for muscle contraction, nerve conduction and blood clotting.

Calcium hydroxide (dentistry)

Strongly alkaline substance used in dentistry as a temporary root canal dressing and for pulp capping. It is antibacterial and can stimulate the formation of hard tissue.

Calcium oxalate

Salt of calcium and oxalic acid that is the most common component of kidney stones. Drinking little, a very oxalate-rich diet and certain bowel diseases increase the risk of calcium oxalate stones.

Calming full-body wash

Wash as part of basal stimulation with warm water in the direction of hair growth and calm, even movements. It is intended to relax and can help with restlessness or sleep problems.

Calmodulin

Calcium-binding regulatory protein found in almost all cells that activates enzymes such as kinases after binding calcium. In smooth muscle it starts contraction via myosin light-chain kinase.

Calot’s triangle

Area between the cystic duct, common hepatic duct and lower edge of the liver in which the cystic artery usually runs. Clearly displaying it during gallbladder removal protects against bile duct injury.

Calprotectin

Inflammatory protein measured in stool that helps distinguish inflammatory bowel disease from irritable bowel syndrome.

CALR mutation

Change in the calreticulin gene that is frequently found in essential thrombocythaemia and primary myelofibrosis when no JAK2 mutation is present. It serves as a diagnostic marker.

CAM-ICU

Short, standardised test for detecting delirium in intensive care patients, even when ventilated. It checks for acute onset, attention, level of consciousness and disorganised thinking.

Cam impingement

Form of hip impingement caused by a bony bump at the junction of the femoral head and neck. Cartilage is damaged during flexion and internal rotation; young, athletic men are often affected.

Cameron lesions

Elongated mucosal defects in the stomach at the level of the diaphragm in a large hiatus hernia. They can bleed chronically and cause iron deficiency anaemia.

Camizestrant

Oral selective oestrogen receptor degrader being studied in hormone receptor-positive breast cancer, including with ESR1 mutation.

Camlipixant

Highly selective P2X3 receptor antagonist being developed for refractory chronic cough. Because of its selectivity, taste disturbances are expected to be less frequent than with older substances.

cAMP

Cyclic adenosine monophosphate, a messenger inside cells that relays signals from hormones such as adrenaline or glucagon. Many drugs work by influencing its formation or breakdown.

Campylobacter

Most common bacterial cause of diarrhoeal illness, often transmitted via poultry.

Camurati-Engelmann disease

Rare inherited bone disease with thickening of the shafts of the long bones. Typical features are bone pain in the legs, muscle weakness and a waddling gait.

Canagliflozin

SGLT2 inhibitor that blocks the reabsorption of sugar in the kidney so that glucose is excreted in the urine. It is used in type 2 diabetes; genital fungal infections and, rarely, ketoacidosis should be watched for.

Canakinumab

Monoclonal antibody against interleukin-1 beta used to treat periodic fever syndromes, Still’s disease and severe gout attacks. The risk of infection is increased during treatment.

Canaliculitis

Inflammation of the fine tear ducts at the corner of the eyelid, often caused by actinomycetes, with a chronically watering eye and pus emerging from the tear punctum. It is often mistaken for conjunctivitis for a long time.

Canavan disease

Autosomal recessive leukodystrophy caused by deficiency of the enzyme aspartoacylase, which leads to accumulation of N-acetylaspartate in the brain. Typical features in infancy are muscle weakness, macrocephaly and severe developmental delay.

Candesartan

Blood-pressure-lowering drug from the sartan group that blocks the angiotensin II receptor. It is used for high blood pressure and heart failure and causes a dry cough less often than ACE inhibitors.

Candida

Yeasts that normally live on the skin and mucous membranes. When immunity is weakened or after antibiotics, they can cause infections such as oral thrush or vaginal thrush.

Candida auris

Yeast that can spread in hospitals and is often resistant to several antifungals. It causes bloodstream infections in seriously ill patients and requires strict hygiene measures.

Candida glabrata

Yeast that, after Candida albicans, is one of the most common Candida species in infections. It is often less susceptible to fluconazole, which influences the choice of therapy.

Candidaemia

Detection of Candida yeasts in the blood, usually in intensive care patients with catheters, antibiotics or weakened immunity. It requires prompt antifungal treatment and a search for secondary sites, for example in the eye.

Cangrelor

Intravenous P2Y12 inhibitor that inhibits platelets very quickly and only briefly. It is used in cardiac catheter procedures when no tablets have been given.

Cannabidiol (CBD)

Non-intoxicating constituent of the hemp plant. As a medicine it is approved for certain rare childhood epilepsies; for over-the-counter CBD products, an effect on other complaints is hardly proven, and interactions with medicines are possible.

Cannabinoid hyperemesis syndrome

Recurrent phases of severe vomiting with long-term, regular cannabis use. Hot showers typically bring relief; in the long term only stopping cannabis helps.

Cannabis use disorder

Problematic cannabis use with loss of control, development of tolerance and continued use despite negative consequences. In adolescents, heavy use can impair brain development.

Capecitabine

Oral precursor of fluorouracil that is converted into the active drug in the tissues. It is used in bowel and breast cancer; hand-foot syndrome with redness and pain of the palms and soles is typical.

See also: Colorectal cancer

Capgras syndrome

Delusional belief that a familiar person has been replaced by an identical-looking impostor. It occurs in schizophrenia, dementias or after brain injury.

Capillariasis

Infection with roundworms of the genus Capillaria. The intestinal form is acquired from raw freshwater fish in South-East Asia and can cause chronic diarrhoea with considerable protein loss.

Capivasertib

Inhibitor of the signalling protein AKT used with fulvestrant in advanced hormone receptor-positive breast cancer with changes in the PI3K/AKT pathway. Raised blood sugar, diarrhoea and rash are typical side effects.

Caplacizumab

Nanobody against von Willebrand factor that prevents platelets from attaching. It is used in acquired thrombotic thrombocytopenic purpura in addition to plasma exchange and immunosuppression.

Caplan syndrome

Occurrence of numerous round nodules in the lungs in people with rheumatoid arthritis who have inhaled dust such as coal or silica.

Capmatinib

MET kinase inhibitor for non-small cell lung cancer with a MET exon 14 skipping mutation. Fluid retention in the legs is typical.

Capnocytophaga

Bacteria from the oral flora of dogs and cats. After bites they can cause life-threatening sepsis, especially in people without a spleen or with alcohol-related disease.

CAPRA score

Score for risk assessment in prostate cancer based on PSA level, Gleason pattern, T stage, percentage of positive biopsy cores and age (0 to 10 points).

Caprini score

Risk model for estimating the risk of thrombosis in surgical patients that scores age, type of procedure, pre-existing conditions and other factors. The type of thrombosis prophylaxis is based on the result.

Capsaicin

Pungent compound from chilli peppers used in patches and creams for nerve and muscle pain. It burns at first and then makes pain fibres less sensitive.

Captopril

First approved ACE inhibitor, with a short duration of action, so it has to be taken several times a day. Typical side effects of the drug class are a dry cough and, rarely, swelling of the skin and mucous membranes.

Caput medusae

Visibly dilated veins of the abdominal skin radiating from the navel. They form as a bypass circulation in portal hypertension, for example in liver cirrhosis.

Caput succedaneum

Soft swelling of the newborn’s scalp caused by pressure during birth, which can extend across skull sutures. It is harmless and usually disappears within a few days.

CAR T-cell therapy

Immunotherapy in which a patient’s own T cells are genetically equipped with a receptor against cancer cells and then returned, for example in certain leukaemias and lymphomas.

CARASIL

Very rare, recessively inherited disease of the small brain vessels with early strokes, dementia, baldness and back pain. It is caused by changes in the HTRA1 gene.

Carbamazepine

Older antiepileptic drug that is also a first-choice treatment for trigeminal neuralgia. It speeds up the breakdown of many other drugs and can affect blood count, sodium levels and the liver.

Carbapenemase

Bacterial enzyme that inactivates carbapenems, one of the last reserves among antibiotics. Carbapenemase-producing organisms are considered particularly dangerous multidrug-resistant germs and are notifiable.

Carbapenems

Very broad-spectrum beta-lactam antibiotics such as meropenem, used mainly for severe hospital-acquired infections and multidrug-resistant pathogens.

Carbetocin

Long-acting modified form of oxytocin given as a single injection after caesarean section so that the uterus contracts and heavy bleeding is avoided.

Carbidopa

Inhibitor of dopa decarboxylase given together with levodopa so that levodopa is not converted to dopamine outside the brain. As a result, levodopa works more strongly and causes less nausea.

Carbimazole

Antithyroid drug converted in the body to thiamazole (methimazole) that inhibits the production of thyroid hormones. It is used in an overactive thyroid; a rare but important side effect is a severe drop in white blood cells (agranulocytosis).

Carbocisteine

Mucolytic that changes the composition of bronchial mucus and is intended to make it easier to cough up. It is used in chronic airway diseases with thick secretions.

Carbohydrate loading

Deliberate filling of the glycogen stores by a carbohydrate-rich diet in the days before a long endurance event. It can improve performance in efforts lasting more than about 90 minutes.

Carboplatin

Platinum compound with a mechanism similar to cisplatin but better tolerated by the kidneys and nerves. The dose is calculated from kidney function; the main side effect is bone marrow suppression.

Carboxyhaemoglobin

Compound of haemoglobin and carbon monoxide that can no longer transport oxygen. Its proportion is measured in blood gas analysis; standard pulse oximeters do not detect it and show falsely high values.

Carboxytherapy

Aesthetic procedure in which medical carbon dioxide is injected under the skin, for example for dark circles or cellulite. The scientific evidence is limited; pain and bruising are possible.

Carcinoma in situ

Earliest stage of cancer, in which the malignant cells are still confined to the surface layer and have not broken through the basement membrane. It therefore cannot yet spread and is usually curable by complete removal.

Cardiobacterium hominis

Member of the HACEK group of slow-growing Gram-negative bacteria of the oral flora. It is a classic but rare cause of endocarditis, often with an insidious course.

Carey Coombs murmur

Soft mid-diastolic heart murmur in acute rheumatic fever caused by the inflamed mitral valve. It usually disappears as the inflammation subsides.

Carfilzomib

Proteasome inhibitor given by infusion in multiple myeloma. It can strain the heart and kidneys, so blood pressure and heart function are monitored.

Carglumic acid

Synthetic analogue of N-acetylglutamate that activates a key enzyme of the urea cycle. It is used in congenital NAGS deficiency and to lower raised ammonia levels in certain organic acidurias.

Carina

Cartilaginous ridge where the windpipe divides into the two main bronchi. It is very sensitive to coughing and is a landmark during bronchoscopy and intubation.

Cariprazine

Third-generation antipsychotic that acts as a partial agonist at dopamine D3 and D2 receptors. It is used in schizophrenia and may also improve lack of drive; restlessness (akathisia) is a typical side effect.

Carmustine

Alkylating cytostatic drug from the nitrosourea group that crosses the blood-brain barrier. It is used in brain tumours, lymphomas and for conditioning before stem cell transplantation, among other things; delayed bone marrow suppression and possible lung damage are typical.

Carnett’s sign

Examination in which the lying patient tenses the abdominal muscles: if tenderness increases, it is more likely to come from the abdominal wall than from internal organs. This helps identify nerve entrapments of the abdominal wall, for example.

Carney complex

Rare inherited condition, usually caused by mutations in the PRKAR1A gene, with spotty skin pigmentation, myxomas (including in the heart) and hormone-producing tumours, for example of the adrenal or pituitary gland.

Carnitine

Compound made by the body that transports long-chain fatty acids into the mitochondria for energy production. The body makes it itself and takes it in with meat; a benefit as a supplement for weight loss or for athletes is not proven.

Carnitine deficiency

Lack of carnitine, which transports fatty acids into the mitochondria; it can be inherited or acquired, for example through dialysis or medication. Consequences may include muscle weakness, weakened heart muscle and low blood sugar during fasting.

Caroli syndrome

Rare congenital malformation with saccular dilations of the bile ducts inside the liver, combined with congenital hepatic fibrosis. Bile stasis favours stone formation and recurrent cholangitis.

Carotid canal

Bony canal in the petrous temporal bone through which the internal carotid artery enters the skull, accompanied by a sympathetic nerve plexus.

Carpenter syndrome

Rare autosomal recessive disorder with premature fusion of skull sutures, extra or fused fingers and toes, obesity and sometimes heart defects.

Carrion’s disease

Infection with Bartonella bacilliformis occurring in the Andes and transmitted by sandflies. The acute phase (Oroya fever) causes severe anaemia, the chronic phase wart-like skin nodules (verruga peruana).

Carteolol

Beta blocker used mainly as eye drops to lower intraocular pressure in glaucoma. Even via the eye it can affect the airways and heart rate.

Carvedilol

Beta blocker with additional vasodilating alpha blockade, used in heart failure and high blood pressure. The dose is increased slowly to avoid dizziness and a drop in blood pressure.

CASPAR criteria

Classification criteria for psoriatic arthritis that, in inflammatory joint, spine or enthesis disease, award points for psoriasis, nail involvement, dactylitis, negative rheumatoid factor and typical X-ray signs.

Caspofungin

Antifungal from the echinocandin group that attacks the fungal cell wall and is given by infusion. It is used mainly in severe Candida infections.

Cattell-Braasch manoeuvre

Extended mobilisation of the right colon and the root of the small bowel mesentery that exposes the retroperitoneum with the aorta, inferior vena cava and duodenum. It is used mainly in trauma surgery.

Catterall classification

Classification of Perthes disease into four groups according to the proportion of the femoral head affected on X-ray. It is used to estimate prognosis but has been supplemented by newer classifications.

Cauda equina

Bundle of lumbar and sacral nerve roots that runs in the spinal canal below the end of the spinal cord, from about the first to second lumbar vertebra. The name means “horse’s tail”.

Cauda equina syndrome

Emergency caused by pressure on the nerve fibres in the lower spinal canal, usually from a large disc herniation. Warning signs are numbness in the genital and buttock area (saddle anaesthesia), bladder or bowel problems and leg weakness; urgent surgery is needed.

CCS classification

Canadian Cardiovascular Society grading of exercise tolerance in stable angina into four grades. Grade IV means symptoms with the slightest exertion or at rest.

CD4 count

Number of CD4-positive T helper cells per microlitre of blood. In HIV it indicates the state of the immune system and helps assess the risk of opportunistic infections.

CDAI

Abbreviation for two activity indices: the Clinical Disease Activity Index for rheumatoid arthritis, which requires no laboratory value, and the Crohn’s Disease Activity Index used to assess Crohn’s disease in trials.

CDK4/6 inhibitors

Oral drugs that inhibit the cell-cycle enzymes CDK4 and CDK6 and so slow the division of tumour cells. They are used with hormone therapy in hormone receptor-positive, HER2-negative breast cancer.

CDKL5 deficiency disorder

Rare X-linked developmental disorder caused by changes in the CDKL5 gene. Typical features are epileptic seizures from the first months of life that respond poorly to medication and marked developmental delay.

CDT (carbohydrate-deficient transferrin)

Variant of the iron transport protein that rises with regular heavy alcohol consumption over several weeks. The value serves as a marker of chronic alcohol use, for example in driving fitness assessments.

CE marking

Mark by which a manufacturer declares that a product meets EU requirements; for medical devices it is a prerequisite for sale.

CEA

Carcinoembryonic antigen, a tumour marker used mainly to monitor bowel cancer. It is not suitable for screening because it can also be raised in smokers and in inflammation.

See also: Colorectal cancer

CEAP classification

International classification of chronic venous disease by clinical picture (C0 to C6), aetiology, anatomical location and pathophysiology. The clinical grades range from invisible changes to an open leg ulcer.

Cefaclor

Oral second-generation cephalosporin for respiratory, ear-nose-throat and urinary tract infections. In children it has been associated with serum sickness-like reactions.

See also: Cephalosporins

Cefadroxil

Oral first-generation cephalosporin active mainly against streptococci and staphylococci. It is used in skin, soft tissue and urinary tract infections and, thanks to its longer half-life, is taken once or twice daily.

Cefalexin

Oral first-generation cephalosporin used in uncomplicated skin, soft tissue and urinary tract infections. It is not active against MRSA and many problematic Gram-negative organisms.

Cefazolin

First-generation cephalosporin antibiotic that works well against staphylococci and streptococci. It is a standard drug for infection prophylaxis before surgery.

Cefepime

Fourth-generation broad-spectrum cephalosporin including Pseudomonas, often used for fever in neutropenia and severe hospital-acquired infections. In kidney failure it can accumulate and cause neurological disturbances up to seizures.

Cefiderocol

Reserve antibiotic from the cephalosporin group that enters Gram-negative bacteria like a Trojan horse via their iron uptake system. It is used for infections with highly resistant pathogens.

See also: Cephalosporins

Cefixime

Oral third-generation cephalosporin that acts mainly against Gram-negative bacteria, for example in urinary tract infections. It is only weakly active against staphylococci.

Cefotaxime

Intravenous third-generation cephalosporin with broad activity against Gram-negative organisms, pneumococci and meningococci. It is used, for example, in meningitis and severe infections, including in newborns.

Cefpodoxime

Oral third-generation cephalosporin with broader activity against Gram-negative bacteria, for example in urinary or respiratory tract infections. It is taken as a prodrug and activated in the gut.

See also: Cephalosporins

Ceftaroline

Newer-generation cephalosporin that, as one of the few beta-lactam antibiotics, is also active against MRSA. It is given intravenously in complicated skin and soft tissue infections and community-acquired pneumonia.

See also: Cephalosporins

Ceftazidime

Third-generation cephalosporin with good activity against Pseudomonas aeruginosa. It is given intravenously in severe hospital-acquired infections and, combined with avibactam, also against certain multidrug-resistant organisms.

Ceftazidime-avibactam

Combination of a cephalosporin and a beta-lactamase inhibitor that covers many multidrug-resistant Gram-negative pathogens. It is regarded as a reserve drug for severe infections.

Ceftobiprole

Newer-generation cephalosporin that is additionally active against MRSA. It is given intravenously for community- and hospital-acquired pneumonia (excluding ventilator-associated pneumonia).

Ceftolozane-tazobactam

Combination of a cephalosporin and a beta-lactamase inhibitor that acts as a reserve antibiotic mainly against multidrug-resistant Pseudomonas aeruginosa, for example in complicated urinary tract and intra-abdominal infections or pneumonia.

Ceftriaxone

Broad-spectrum third-generation cephalosporin given by infusion or injection. It is a standard treatment for severe bacterial infections such as meningitis or pneumonia.

See also: Cephalosporins

Celecoxib

COX-2-selective pain and anti-inflammatory drug that causes stomach ulcers less often than conventional NSAIDs. Caution is needed in cardiovascular disease and reduced kidney function.

Celiprolol

Beta blocker with an additional mild vasodilating effect. It is also studied and used in the vascular form of Ehlers-Danlos syndrome to prevent arterial ruptures.

Cellulite

Dimpled change in the skin surface on the thighs and buttocks, mainly in women, caused by the structure of the connective tissue. It is medically harmless.

In depth: Cellulite →

Cemiplimab

PD-1 checkpoint inhibitor used, among other indications, in advanced cutaneous squamous cell carcinoma. Like other immunotherapies, it can trigger immune-mediated inflammation of various organs.

Cenobamate

Newer antiepileptic drug for focal seizures that do not respond adequately to other medicines. It must be increased slowly because of possible severe skin reactions.

Centor score

Score to estimate whether tonsillitis is caused by streptococci. It takes into account fever, tonsillar exudate, swollen neck lymph nodes and absence of cough.

Central core disease

Congenital, usually mild muscle disease with weakness of muscles near the trunk, often caused by changes in the RYR1 gene. Those affected have an increased risk of malignant hyperthermia with certain anaesthetics.

Centrum semiovale

Large area of white matter in the cerebrum above the lateral ventricles that appears semi-oval in cross-section. Changes due to small vessel disease are often seen here.

Cephalosporins

Large group of beta-lactam antibiotics related to penicillins and classified into generations according to their spectrum. They are among the most widely used antibiotics; cross-allergy with penicillin is rare but possible.

Ceramides

Skin lipids that act as “mortar” between the horny cells and form the skin barrier; they are used in care products for dry skin.

Cerebral contusion

Bruising of the brain with visible injury to brain tissue after traumatic brain injury, often with prolonged unconsciousness and neurological deficits. Unlike concussion, it is visible on imaging.

Ceritinib

Second-generation ALK kinase inhibitor for ALK-positive non-small cell lung cancer. Common side effects are gastrointestinal complaints and raised liver values.

Cerliponase alfa

Enzyme replacement therapy for neuronal ceroid lipofuscinosis type 2 (CLN2), a rare childhood dementia. The enzyme is given directly into the brain ventricles via an implanted reservoir to slow the course of the disease.

Certolizumab pegol

PEGylated antibody fragment against TNF-alpha used to treat rheumatoid arthritis, axial spondyloarthritis, psoriatic arthritis and psoriasis. Because it lacks the Fc part, it hardly crosses the placenta.

Certoparin

Low-molecular-weight heparin injected under the skin to prevent and treat thrombosis. Like other heparins, it can rarely cause heparin-induced thrombocytopenia, so the platelet count is monitored.

Cervical canal

Mucus-filled canal in the cervix that connects the uterine cavity and the vagina. Its mucus plug changes during the menstrual cycle and in pregnancy.

Cervical cerclage

Surgically placed band around the cervix intended to keep it closed during pregnancy when cervical weakness threatens, to prevent preterm birth. Benefits and risks are weighed individually.

Cetirizine

Antihistamine for hay fever and hives; it can cause mild drowsiness.

Cetrorelix

GnRH antagonist that prevents premature ovulation in fertility treatment. It is injected under the skin and acts rapidly without an initial hormone surge.

Cetuximab

Monoclonal antibody against the EGF receptor used in metastatic bowel cancer without RAS mutation and in squamous cell carcinomas of the head and neck. Typical effects are an acne-like rash, infusion reactions and magnesium loss.

See also: Colorectal cancer

CGRP antibodies

Monoclonal antibodies that block the messenger CGRP or its receptor and are injected monthly or quarterly to prevent frequent migraine attacks.

CH50

Laboratory test that measures the total activity of the classical complement pathway. A markedly reduced value may indicate a congenital complement defect or consumption in active immune complex diseases such as lupus.

CHA2DS2-VASc score

Points system to estimate stroke risk in atrial fibrillation, taking into account age, high blood pressure, diabetes, heart failure and previous stroke, among other factors. It helps decide on anticoagulation.

Chaddock reflex

Pathological reflex in which stroking the outer edge of the foot below the lateral malleolus causes the big toe to extend upwards. Like the Babinski sign, it indicates damage to the pyramidal tract.

Chagas disease

Parasitic infection with Trypanosoma cruzi transmitted by triatomine bugs in Latin America. Decades after infection, heart muscle damage and organ enlargement can occur.

Chair rise test

Functional test in which a person stands up from a chair five times as quickly as possible without using their arms. A long time indicates reduced leg strength and an increased risk of falls and sarcopenia.

Chalazion

Painless lump on the eyelid caused by a blocked gland.

Chance fracture

Transverse fracture through the vertebral body and arch caused by severe flexion, classically from a lap seatbelt in a car. Abdominal organs are often injured at the same time.

Char syndrome

Autosomal dominant inherited disease with patent ductus arteriosus, a typical face with a short philtrum and flat nasal bridge, and malformations of the little finger. It is caused by mutations in the TFAP2B gene.

Charcot foot

Destruction of foot bones and joints due to nerve damage, usually in diabetes. Initially the foot is warm and swollen, often without much pain.

Charcot-Marie-Tooth disease

Most common inherited nerve disease, with muscle wasting in the lower legs and feet, high-arched feet and sensory disturbances.

Charcot’s triad

Combination of fever (often with rigors), jaundice and pain in the right upper abdomen. It indicates acute cholangitis, usually due to bile duct obstruction.

CHARGE syndrome

Rare malformation syndrome, usually caused by changes in the CHD7 gene. The name summarises typical findings: coloboma, heart defects, choanal atresia, retarded growth and development, genital anomalies and ear anomalies.

Charles Bonnet syndrome

Vivid, often detailed visual hallucinations in people with severe vision loss, for example due to macular degeneration, without mental illness. Those affected know the images are not real; explanation brings great relief.

Charlson Comorbidity Index

Score that weights coexisting conditions such as heart failure, diabetes or cancer according to their impact on mortality. It is used in studies and treatment planning to estimate risk.

Checkpoint inhibitors

Cancer drugs that release the “brakes” of the immune system so that T cells can attack tumour cells again, for example in melanoma or lung cancer.

Chediak-Higashi syndrome

Rare inherited immunodeficiency with giant granules in white blood cells, light skin and hair pigmentation, susceptibility to infection and a bleeding tendency. Without stem cell transplantation, a life-threatening over-activation of the immune system can occur.

Cheilitis

Inflammation of the lips with dryness, cracks or scaling, for example due to cold, saliva, contact allergies or fungi.

Chemical peel

Treatment in which acids remove the upper layers of the skin in a controlled way to improve skin texture, pigment spots or fine lines.

In depth: Chemical Peel →

Chemical UV filter

Organic sunscreen substances that absorb UV radiation in the skin and convert it into heat. They can be applied invisibly; rarely, individual filters cause contact allergies.

Chemokines

Small messengers of the immune system that attract immune cells specifically to the site of inflammation. Some viruses such as HIV also use their receptors as an entry route.

Chemoreceptors

Sensory cells that detect chemical stimuli. For breathing, peripheral chemoreceptors in the carotid body mainly sense lack of oxygen, and central ones in the medulla mainly sense CO2 and pH.

Chemosis

Glassy swelling of the conjunctiva due to fluid accumulation, often in allergic reactions, inflammation or impaired drainage in the eye socket. When pronounced, the conjunctiva can bulge over the eyelid margin.

Chemotaxis

Directed movement of cells along a chemical concentration gradient, for example of immune cells to the site of inflammation. Messengers such as chemokines and bacterial components attract them.

Chemotherapy

Treatment with drugs (cytostatics) that damage rapidly dividing cells, especially cancer cells. Because healthy fast-dividing cells are also affected, side effects such as hair loss or nausea occur.

Chemotherapy-induced peripheral neuropathy

Nerve damage caused by cytostatic drugs such as platinum compounds, taxanes or vincristine. Tingling, numbness and pain in the hands and feet may require dose adjustments and can persist for a long time.

Chenodeoxycholic acid

Primary bile acid used as a medicine in the rare disease cerebrotendinous xanthomatosis. It was formerly also used to dissolve gallstones.

Cherubism

Rare inherited condition in which bone in the upper and lower jaw is replaced by cystic tissue in childhood, giving the cheeks a chubby appearance. It often regresses after puberty.

Chest tightness

Feeling of pressure or constriction in the chest. It can be a sign of reduced blood flow to the heart and should be assessed by a doctor promptly, especially if it occurs on exertion or with breathlessness.

Chevron osteotomy

Operation for mild to moderate hallux valgus in which the head of the first metatarsal is cut in a V shape and shifted outwards.

Cheyne-Stokes respiration

Periodic breathing pattern in which breaths wax and wane and are interrupted by pauses. It occurs mainly in severe heart failure, after stroke or during sleep at high altitude.

Chi-squared test

Statistical test for frequency data that checks whether observed frequencies in a contingency table differ from those expected. With small numbers, Fisher’s exact test is usually used instead.

Chiari malformation

Congenital malformation in which parts of the cerebellum extend through the large opening at the base of the skull into the spinal canal. Many people have no symptoms; possible features are back-of-head pain on coughing or straining and neurological deficits.

Chiari pelvic osteotomy

Operation to improve coverage of the femoral head in which the pelvis is cut transversely above the socket and shifted inwards. Today it is used mainly as a salvage procedure.

Chicago classification

Diagnostic scheme for classifying oesophageal motility disorders based on high-resolution manometry, currently in version 4.0. It distinguishes achalasia types I to III from other motility disorders, among others.

Chikungunya fever

Mosquito-borne viral disease with high fever and severe joint pain that can persist for weeks to months. It occurs mainly in tropical regions; approved vaccines are recommended only with restrictions for older people in some cases.

Chikungunya vaccination

Vaccination against the mosquito-borne chikungunya virus, available as a live vaccine and as a virus-like particle vaccine. Safety concerns about the live vaccine emerged in older people, so recommendations were adjusted.

Chilaiditi syndrome

Symptoms caused by a loop of bowel lying between the liver and the diaphragm. The X-ray finding alone without symptoms is called Chilaiditi’s sign and can be mistaken for free air in the abdomen.

Chilblain lupus

Rare form of cutaneous lupus with chilblain-like, bluish-red nodules on the fingers, toes, nose or ears triggered by cold. Some of those affected develop systemic lupus.

Child-Pugh score

Classification of the severity of liver cirrhosis into stages A to C. It assesses bilirubin, albumin, clotting, ascites and hepatic encephalopathy.

Chimerism

Presence in one organism of cells with different genetic material derived from different fertilised eggs or individuals. It is medically important after stem cell transplantation, where the donor proportion in the blood is monitored.

Chiropractic

Manual treatment focusing on the spine in which joints are mobilised with targeted manipulations. It may help in the short term for some back pain; rare but serious risks such as injury to neck arteries are known.

Chlamydia

Bacteria that cause, among other things, one of the most common sexually transmitted infections. It often causes no symptoms but, if untreated, can lead to infertility.

Chlamydia pneumoniae

Bacterium that can survive only inside cells and is transmitted by droplets. It causes respiratory infections and atypical pneumonia, often mild and with a lingering cough.

Chlamydia psittaci

Bacterium transmitted mainly from parrots, pigeons and other birds via dust from droppings and feathers. In humans it causes psittacosis with fever, headache and atypical pneumonia.

Chlamydia trachomatis

Intracellular bacterium and the most common bacterial cause of sexually transmitted infections. Certain serotypes cause trachoma, one of the most common infectious causes of blindness worldwide.

Chloracne

Severe acne-like skin disease after contact with halogenated hydrocarbons such as dioxins. Typical are numerous blackheads and cysts on the face and behind the ears; it is regarded as a warning sign of significant toxic exposure.

Chlorambucil

Orally taken, slow-acting alkylating agent that was used mainly in older people with chronic lymphocytic leukaemia or slow-growing lymphomas. It has lost much of its importance because of modern targeted therapies.

Chloramphenicol

Broad-spectrum antibiotic hardly used systemically any more because of the risk of irreversible aplastic anaemia. In newborns it can cause life-threatening grey baby syndrome; topically it is still contained in some eye preparations.

Chlordiazepoxide

The first benzodiazepine brought to market, with a long half-life. It is used mainly in alcohol withdrawal; risks include drowsiness, respiratory depression and dependence.

Chlorhexidine

Disinfectant used in mouthwashes and skin antiseptics. Prolonged use in the mouth can stain teeth and tongue.

Chloride

Important blood electrolyte that, together with sodium, helps regulate fluid and acid-base balance. In the sweat test, a raised chloride level is used to diagnose cystic fibrosis.

Chlorine gas poisoning

Poisoning by chlorine gas, for example when mixing cleaning products or in swimming pool accidents, with cough, breathlessness and eye irritation. In severe cases pulmonary oedema develops.

Chlormadinone acetate

Synthetic progestogen with anti-androgenic effects, used in combination with ethinylestradiol in contraceptive pills. It can have a favourable effect on androgen-related acne and hair problems.

Chloroprocaine

Short-acting ester-type local anaesthetic used for spinal anaesthesia in short day-case procedures. It is rapidly broken down in the blood.

Chloroquine

Older antimalarial drug to which Plasmodium falciparum is resistant in most regions. Long-term use can damage the retina; in rheumatology the related hydroxychloroquine is usually used.

Chlorprothixene

Low-potency antipsychotic with a strong sedative effect, used for restlessness, agitation and sleep disorders in mental illness. It can cause a drop in blood pressure and dry mouth.

Chlortalidone

Long-acting thiazide-like diuretic that increases salt and water excretion by the kidneys and lowers blood pressure. Sodium, potassium and uric acid should be monitored.

Choanae

Rear openings of the nasal cavity through which the nose passes into the nasopharynx. Congenital closure (choanal atresia) can cause breathing difficulty in newborns.

Choanal atresia

Congenital closure of the rear nasal openings. When both sides are affected, it is an emergency for newborns, who breathe mainly through the nose.

Cholangiocarcinoma

Malignant tumour of the bile ducts that often first shows as painless jaundice. Risk factors include primary sclerosing cholangitis and chronic liver disease.

Cholangitis

Inflammation of the bile ducts, often due to a gallstone blocking drainage. Typical features are fever, upper abdominal pain and jaundice; it needs prompt treatment.

Cholecystectomy

Surgical removal of the gallbladder, usually by keyhole surgery, for symptoms caused by gallstones or after gallbladder inflammation. Without a gallbladder, bile flows directly into the gut; most people have no symptoms afterwards.

Cholecystitis

Inflammation of the gallbladder, usually caused by a gallstone blocking drainage. Typical features are persistent pain in the right upper abdomen and fever; the gallbladder is usually removed promptly.

Cholecystokinin

Gut hormone that makes the gallbladder contract after fatty meals and promotes the release of digestive enzymes. It also contributes to the feeling of fullness.

Choledochal cyst

Congenital cystic dilation of the bile ducts, more common in women and in East Asia. It causes abdominal pain, jaundice or inflammation and is usually removed surgically because of an increased cancer risk.

Cholera

Intestinal infection caused by the bacterium Vibrio cholerae with massive watery diarrhoea that can quickly lead to life-threatening fluid loss. Rapid replacement of fluid and salts is crucial.

Cholera vaccination

Oral vaccine containing inactivated cholera bacteria and toxin components. It is recommended for travellers at particular risk, such as aid workers in outbreak areas, and does not protect completely.

Cholestasis

Impaired bile flow in which bile does not drain adequately into the gut. It can cause jaundice, itching, pale stools and dark urine.

Cholesteatoma

Growth of keratinising squamous epithelium in the middle ear that slowly destroys bone. Typical signs are foul-smelling ear discharge and hearing loss; treatment is surgical.

Cholesterol

Fat-like substance the body needs for cell membranes and hormones. A high level of LDL cholesterol (“bad” cholesterol) promotes atherosclerosis, while HDL cholesterol is considered protective.

Cholesterol embolism

Dislodgement of cholesterol crystals from ruptured atherosclerotic plaques into small vessels, often after cardiac catheterisation or vascular surgery. Consequences include blue-violet toes, mottled skin and kidney failure.

Choline

Vitamin-like nutrient needed for cell membranes, liver fat metabolism and production of the messenger acetylcholine. Good sources are eggs, liver and meat; requirements increase during pregnancy.

Cholinergic syndrome

Poisoning caused by overstimulation of acetylcholine receptors, for example by insecticides (organophosphates) or nerve agents. Typical signs are small pupils, salivation, sweating, diarrhoea, slow pulse and muscle twitching; atropine is the most important antidote.

Cholinergic urticaria

Form of hives with many small, itchy wheals that appear when the body warms up through exercise, hot showers or excitement. It mainly affects young adults.

Cholinesterase

Liver enzyme in the blood whose level reflects the liver’s synthetic capacity. Low levels are found in liver cirrhosis and certain poisonings, for example with insecticides.

Chondrocalcinosis

Deposition of calcium pyrophosphate crystals in cartilage that can trigger acute gout-like joint inflammation.

Chondrocyte

Cartilage cell that produces the collagen and proteoglycans of the cartilage matrix. Because joint cartilage has no blood vessels, chondrocytes regenerate only to a very limited extent.

Chondrodermatitis nodularis helicis

Painful nodule on the rim of the ear, usually in older people, caused by pressure on the ear cartilage during sleep. Pressure relief and, if necessary, minor surgery help.

Chondroitin

Natural component of cartilage often taken together with glucosamine for osteoarthritis symptoms. The evidence is conflicting.

Chondromalacia

Softening and roughening of cartilage, especially on the back of the kneecap. It causes pain when climbing stairs and sitting for long periods and is mainly treated with physiotherapy.

Chondromalacia patellae

Softening and damage of the cartilage on the back of the kneecap that causes pain, especially in young people, when climbing stairs, squatting or sitting for long periods. Strength training of the thigh muscles often helps.

Chondrosarcoma

Malignant bone tumour made of cartilage tissue that occurs mainly in adults in the pelvis, thigh or shoulder.

Chopart joint

Transverse joint line of the tarsus between the talus and calcaneus on one side and the navicular and cuboid bones on the other. It allows rotational and tilting movements of the forefoot.

Chorda tympani

Branch of the facial nerve that passes through the middle ear and carries taste fibres from the front two-thirds of the tongue as well as fibres to the submandibular and sublingual salivary glands. It can be injured during middle ear surgery.

Chordae tendineae

Fine tendinous cords that connect the leaflets of the mitral and tricuspid valves to the papillary muscles. They stop the leaflets from flipping back into the atria when the heart contracts; a rupture causes acute valve leakage.

Chordoma

Rare, slow-growing malignant bone tumour arising from remnants of the embryonic notochord, usually at the skull base or sacrum. Treatment consists of surgery that is as complete as possible and often proton or heavy-ion radiotherapy.

Chorea

Involuntary, rapid, irregular movements that seem to flow from one part of the body to another. Causes include Huntington’s disease, medicines, pregnancy or autoimmune processes after streptococcal infection.

Choriocarcinoma

Malignant tumour of trophoblast tissue that can develop after a hydatidiform mole, miscarriage or pregnancy. It produces hCG, which serves as a marker, and usually responds very well to chemotherapy.

Chorion

Outer fetal membrane surrounding the embryo, from whose villi the fetal part of the placenta forms. Its tissue can be examined in chorionic villus sampling.

Chorionic villus sampling

Prenatal test in which tissue from the developing placenta is taken from about the 11th week of pregnancy and analysed genetically. The procedure-related risk of miscarriage is low but present.

Chorioretinitis

Inflammation of the choroid and retina, often due to toxoplasmosis, cytomegalovirus or autoimmune diseases. It presents with blurred vision and vitreous floaters and can leave scars with visual field defects.

Choroidal haemangioma

Benign, orange-red vascular tumour of the choroid. The circumscribed form usually occurs alone, the diffuse form in Sturge-Weber syndrome; if vision is reduced, photodynamic therapy can be considered.

Choroideremia

X-linked inherited retinal disease in which the choroid and retina progressively waste away. It usually begins with night blindness in childhood and leads to visual field loss.

Chromatin

Complex of DNA and packaging proteins (histones) in the cell nucleus. How densely it is packed influences which genes can be read; this is a central mechanism of epigenetics.

Chromatopsia

Visual disturbance in which the surroundings appear tinted, for example yellow in digitalis poisoning. A temporary blue tinge can also be noticed after cataract surgery.

Chromhidrosis

Rare secretion of coloured sweat, for example yellowish, green or black, usually from apocrine glands on the face or in the armpits. It is harmless but can be distressing.

Chromoblastomycosis

Chronic fungal infection of the skin and subcutaneous tissue in tropical regions that develops after minor injuries, often on the legs. Slowly growing, wart-like nodules and plaques form that are difficult to treat.

Chromoendoscopy

Endoscopic technique in which the mucosa is stained with dyes such as indigo carmine or methylene blue to better detect flat lesions and their surface patterns. It is used, for example, in surveillance of inflammatory bowel disease.

Chromogranin A

Protein from the storage vesicles of hormone-producing cells, used as a tumour marker for neuroendocrine tumours. Proton pump inhibitors and reduced kidney function can falsely raise the level.

Chromosome

Coiled strand of DNA in the cell nucleus. Humans normally have 46 chromosomes in 23 pairs.

Chronaxie

Stimulus duration needed to trigger excitation at twice the rheobase current. A prolonged value can indicate damage to the supplying nerve.

Chronic

Developing slowly and lasting a long time or recurring repeatedly. The opposite of acute.

Chronic lymphocytic leukaemia

The most common leukaemia in adults, in which mature but non-functional B lymphocytes accumulate. It often progresses slowly and in early stages is frequently just monitored.

Chronic myeloid leukaemia

Blood cancer in which a chromosomal rearrangement (Philadelphia chromosome) produces a permanently active enzyme. Tyrosine kinase inhibitors such as imatinib have fundamentally improved the outlook.

Chronic myelomonocytic leukaemia

Blood cancer of older people with persistently raised monocytes that combines features of a myelodysplastic syndrome and a myeloproliferative neoplasm. It can progress to acute leukaemia.

Chronic pain

Pain lasting longer than three to six months that often becomes a condition in its own right; it is usually treated with a multimodal approach.

Chronic pancreatitis

Progressive inflammation of the pancreas in which functional tissue is gradually replaced by scar tissue; the most common causes are alcohol and smoking. Consequences are recurrent upper abdominal pain, fatty stools due to digestive enzyme deficiency and later diabetes.

Chronic rhinosinusitis

Inflammation of the nasal lining and sinuses lasting longer than twelve weeks, with a blocked nose, discharge and reduced sense of smell. It occurs with or without nasal polyps; rinses and corticosteroid sprays are the basis of treatment.

Chronic thromboembolic pulmonary hypertension

Form of pulmonary hypertension in which scarred clots permanently narrow the pulmonary arteries after one or more pulmonary emboli. It is the only form of pulmonary hypertension that is potentially curable by surgery (pulmonary endarterectomy); balloon angioplasty or riociguat are alternatives.

Chronic venous insufficiency

Persistently impaired return of blood in the leg veins, with swelling, skin changes and, in late stages, open sores.

Chronic wound

Wound that has not healed after about eight weeks despite proper treatment, such as a leg ulcer, pressure ulcer or diabetic foot ulcer. Treating the cause, for example compression, pressure relief or blood sugar control, is crucial.

Chronification

Transition of an initially acute illness or complaint into a persistent condition. In pain, both physical and psychological factors contribute, such as avoidance behaviour, anxiety and stress.

Chronotropy

Influence on heart rate. Adrenaline and the sympathetic nervous system have a positive chronotropic effect, the vagus nerve and beta blockers a negative one.

Chvostek’s sign

Twitching of the facial muscles when the facial nerve is tapped in front of the ear. It can indicate low calcium with increased nerve excitability.

Chylomicrons

Large fat-protein particles formed in the gut that carry dietary fats via the lymph into the blood. After fatty meals they make the blood serum look milky and cloudy.

Chylothorax

Collection of milky lymph fluid in the pleural space, usually after injury to the thoracic duct or due to tumours.

Chyluria

Milky, cloudy urine due to the admixture of lymph fluid (chyle), usually because of a connection between lymphatic vessels and the urinary tract. The most common cause worldwide is lymphatic filariasis.

Ciclesonide

Inhaled corticosteroid for asthma that is converted to its active form only in the lungs. As a result, oral thrush occurs less often than with some other inhaled steroids.

Ciclopirox

Broad-spectrum antifungal used as a nail lacquer for nail fungus and as a cream or shampoo. For nail fungus, the lacquer must be applied over many months until the nail has grown out.

Ciclosporin

Immunosuppressant from the calcineurin inhibitor group used after organ transplantation and in severe autoimmune diseases. Because of possible kidney damage, high blood pressure and many interactions, for example with grapefruit, blood levels are monitored.

Cidofovir

Antiviral against cytomegalovirus and other DNA viruses, given intravenously at longer intervals. Because of its strong kidney toxicity, it is given together with probenecid and plenty of fluid.

CIDP

Chronic inflammatory demyelinating polyneuropathy, in which the immune system attacks the insulating layer of peripheral nerves. Weakness and sensory disturbances in the arms and legs develop over more than eight weeks; immunoglobulins, corticosteroids or plasma exchange can help.

Ciguatera

Fish poisoning caused by ciguatoxins that accumulate in tropical reef fish. Typical features are diarrhoea, tingling and a reversal of temperature sensation; the nerve symptoms can last for weeks.

Ciliospinal reflex

Dilation of the pupil after a painful stimulus to the neck or face, mediated by the sympathetic nervous system. It is tested, among other situations, in unconscious patients to assess the brainstem.

Cilostazol

Phosphodiesterase-3 inhibitor that can increase walking distance in peripheral arterial disease with claudication. It must not be used in heart failure; headache and diarrhoea are common.

Ciltacabtagene autoleucel

CAR T-cell therapy directed against the surface marker BCMA for the treatment of multiple myeloma. Typical risks are cytokine release syndrome and neurological side effects.

Cimex lectularius

Common bedbug, a wingless insect a few millimetres long that sucks blood at night and hides in crevices during the day. The bites cause itchy wheals, often arranged in rows.

Cimino fistula

Surgically created connection between a forearm artery and a vein, usually at the wrist, so that the vein can be easily punctured for haemodialysis. The fistula arm should not be used for blood pressure measurement or blood sampling.

Cinacalcet

Calcimimetic that makes the calcium sensor of the parathyroid glands more sensitive and thus lowers parathyroid hormone release. It is used mainly in secondary hyperparathyroidism in dialysis patients.

Cinnarizine

Antihistamine with calcium-antagonist activity used against vertigo and motion sickness. It is often combined with dimenhydrinate; drowsiness is a typical side effect.

Circle of Willis

Ring-shaped connection of arteries at the base of the brain that links the carotid and vertebral arteries. It can redirect blood flow if individual supply vessels narrow and is a typical site of brain aneurysms.

Cisatracurium

Non-depolarising muscle relaxant that breaks down spontaneously in the blood independently of the liver and kidneys. It is therefore particularly suitable in organ failure, for example in intensive care.

Cisplatin

Platinum-containing cytostatic drug that cross-links the DNA of cancer cells and so prevents them from dividing. It is used in many solid tumours; severe nausea and kidney and hearing damage are typical, so plenty of fluid is given.

Cisterna chyli

Sac-like widening at the start of the thoracic duct in front of the lumbar spine, where lymph from the abdomen and legs collects.

Cisterna magna

Largest widening of the subarachnoid space, located between the cerebellum and the medulla oblongata. It is filled with cerebrospinal fluid and assessed as a landmark in prenatal diagnosis and imaging.

Citalopram

SSRI antidepressant prescribed for depression and anxiety disorders. At higher doses it can prolong the QT interval on the ECG.

Citric acid cycle

Central metabolic pathway in the mitochondria in which breakdown products of sugar, fat and protein are converted to carbon dioxide and energy-rich electron carriers are gained. Also called the Krebs cycle.

Citrobacter freundii

Gut bacterium of the Enterobacterales family. It causes urinary tract, wound and bloodstream infections, mainly in hospitals, and can become resistant to many beta-lactam antibiotics through an AmpC enzyme.

Citrullinaemia

Inherited urea cycle disorder in which ammonia and citrulline accumulate in the blood. The classic form appears in newborns with poor feeding, vomiting and impaired consciousness.

CIWA-Ar

Clinical scale for assessing the severity of alcohol withdrawal syndrome based on symptoms such as tremor, sweating, agitation and hallucinations. It often guides symptom-triggered medication.

CK-MB

Heart-muscle-specific form of the enzyme creatine kinase that enters the blood when heart muscle is damaged. It has largely been replaced by the more sensitive troponin in heart attack diagnosis but can help detect a reinfarction.

CKD-EPI equation

Equation for estimating the glomerular filtration rate (eGFR) from serum creatinine, age and sex, optionally supplemented by cystatin C. It is the usual standard formula used by laboratories for adults.

CKD-MBD

Chronic kidney disease-mineral and bone disorder: disturbances of mineral and bone metabolism in chronic kidney disease. These include altered calcium, phosphate, parathyroid hormone and FGF23 levels, bone changes and vascular calcification.

Cladophialophora

Genus of darkly pigmented (dematiaceous) moulds. Some species cause chromoblastomycosis of the skin, and Cladophialophora bantiana also causes rare, severe brain abscesses.

Cladribine

Purine analogue that selectively reduces lymphocytes. As a short course of tablets in two yearly cycles it is used in highly active multiple sclerosis, and as an infusion in hairy cell leukaemia.

Clark level

Classification of the depth of invasion of a melanoma into five levels according to the skin layers involved. For staging, Breslow thickness has largely replaced the Clark level.

Clascoterone

Topical drug that blocks androgen receptors in the sebaceous glands and thus reduces sebum production. It is used as a cream for acne; skin irritation is a common side effect.

Claustrum

Thin sheet of grey matter between the insular cortex and the putamen with extensive connections to the cerebral cortex. Its exact function is not yet clear; a role in attention and consciousness is discussed.

Clavien-Dindo classification

Five-grade classification of complications after surgery according to the treatment required, from deviations without specific therapy (grade I) to death (grade V). It makes complication rates comparable between studies and hospitals.

Clay-shoveler’s fracture

Fatigue or avulsion fracture of a spinous process at the junction of the cervical and thoracic spine, usually at the seventh cervical vertebra. It is generally stable and treated conservatively.

Clearance

Measure of the volume of blood plasma completely cleared of a substance per unit of time. It describes how quickly the kidney or liver eliminates a drug.

Clemastine

First-generation antihistamine that also causes drowsiness and has anticholinergic effects. Today it is used mainly intravenously in acute allergic reactions.

Clesrovimab

Long-acting monoclonal antibody against the F protein of respiratory syncytial virus, intended to protect newborns and infants during their first RSV season with a single injection.

Clevidipine

Short-acting calcium channel blocker for intravenous blood pressure reduction that is rapidly broken down in the blood and therefore easy to control. It is used perioperatively and in hypertensive emergencies; as a lipid emulsion it is unsuitable in soy or egg allergy.

Clindamycin

Antibiotic that penetrates bone and tissue well and is used, for example, in skin, dental and bone infections. It increases the risk of Clostridioides difficile colitis.

Clinical Dementia Rating

Graded scale that rates the severity of dementia in six domains such as memory, orientation, judgement and personal care (0 = none to 3 = severe dementia).

Clinical Frailty Scale

Nine-point scale for assessing frailty in older people, from very fit to terminally ill, based on daily functioning and activity. It is used in emergency and intensive care medicine to estimate prognosis.

Clivus

Sloping bony surface at the base of the skull between the sella turcica and the foramen magnum, on which the brainstem lies. Rare tumours such as chordomas can arise here.

Clobazam

Benzodiazepine used as an add-on drug in difficult-to-treat epilepsies, for example Lennox-Gastaut syndrome. With continuous use the effect may wane, and drowsiness is common.

Clobetasol

Very potent topical corticosteroid used, for example, in psoriasis or lichen sclerosus. It is used only briefly and on small areas because it can thin the skin.

Clofarabine

Purine nucleoside analogue for treating relapsed or refractory acute lymphoblastic leukaemia in children and adolescents. It inhibits DNA synthesis; possible complications are capillary leak syndrome and tumour lysis syndrome.

Clofazimine

Red-coloured drug against mycobacteria that is part of combination therapy for leprosy and is also used in resistant tuberculosis. A typical side effect is reddish-brown discolouration of the skin and body fluids.

Clomethiazole

Sedative and hypnotic used mainly in the inpatient treatment of alcohol withdrawal. Because of its high dependence potential and respiratory depression, especially with alcohol, outpatient use is problematic.

Clomifene

Hormonally active drug that stimulates egg maturation and is used in people trying to conceive who do not ovulate. Multiple pregnancies are more frequent than usual.

Clomipramine

Tricyclic antidepressant with particularly strong inhibition of serotonin reuptake. It is used in depression and obsessive-compulsive disorder; dry mouth, constipation, sweating and heart rhythm changes are possible side effects.

Clonazepam

Long-acting benzodiazepine used mainly against epileptic seizures. Like all benzodiazepines, it can cause drowsiness and dependence with long-term use.

Clonidine

Centrally acting alpha-2 agonist that dampens the sympathetic nervous system and thus lowers blood pressure. It is also used in alcohol and opioid withdrawal, for sedation in intensive care and in ADHD; stopping it suddenly can cause a rise in blood pressure.

Clonorchiasis

Infection with the Chinese liver fluke Clonorchis sinensis from raw freshwater fish, mainly in East Asia. Chronic bile duct inflammation increases the risk of bile duct cancer.

Clopidogrel

Drug that inhibits the clumping of platelets, for example after stent placement or a heart attack, often combined with aspirin.

Clostridioides difficile

Gut bacterium that can multiply, especially after antibiotic treatment, and cause severe diarrhoea.

Clostridium botulinum

Spore-forming anaerobic bacterium that produces the nerve poison botulinum toxin. Poisoning usually results from improperly preserved food and leads to paralysis.

Clostridium perfringens

Spore-forming anaerobic bacterium that can cause gas gangrene in deep wound infections. Certain strains also produce toxins in food that has not been cooled adequately, causing food poisoning.

Clostridium septicum

Bacterium that can cause spontaneous gas gangrene without an external wound, which rapidly becomes life-threatening. Such an infection is often associated with bowel cancer or blood cancer, so these are specifically looked for.

See also: Colorectal cancer

Clostridium tetani

Spore-forming bacterium from soil and dust that enters through wounds and produces the toxin tetanospasmin. This causes tetanus; vaccination provides reliable protection.

Clotrimazole

Azole antifungal used as a cream, solution or vaginal tablet for fungal infections of the skin and vagina. Treatment should continue for some time after symptoms have resolved.

Clozapine

Antipsychotic used in schizophrenia when other drugs have not worked well enough. Because it can rarely cause a dangerous drop in white blood cells, regular blood count checks are mandatory.

Club cells

Dome-shaped, non-ciliated cells in the lining of the smallest bronchioles, formerly called Clara cells. They produce protective proteins, detoxify foreign substances and serve as progenitor cells during regeneration.

Cluster headache

Very severe, one-sided headache attacks around the eye that occur in series, often with a watering eye.

Cluster randomised trial

Trial in which whole groups such as practices, schools or wards, rather than individuals, are randomly allocated to the comparison arms. It usually needs more participants and special analysis methods.

CMV retinitis

Retinal inflammation caused by cytomegalovirus that occurs almost only in severe immunodeficiency, for example in advanced HIV infection. Untreated, it leads to blindness.

Co-trimoxazole

Combination of the antibiotics sulfamethoxazole and trimethoprim, used for example in urinary tract infections and to prevent Pneumocystis pneumonia. It can cause skin reactions and raised potassium levels.

CO2 laser

Ablative laser that vaporises tissue and is used in dermatology to remove skin growths and, in fractional mode, to smooth the skin. Risks include longer healing times, pigment changes and scarring.

Coats disease

Usually one-sided, congenital malformation of the retinal blood vessels with leakage of fluid and lipids under the retina. It mainly affects boys and, like retinoblastoma, can cause a white pupil.

Cobb angle

Angle measured on an X-ray between the most tilted vertebrae of a spinal curve. A curve of 10 degrees or more is called scoliosis; the value guides treatment.

Cobicistat

Pharmacokinetic enhancer without antiviral activity of its own that inhibits the enzyme CYP3A4 and thereby raises the levels of certain HIV drugs. It can slightly increase creatinine without actually worsening kidney function.

Cobimetinib

MEK inhibitor used together with the BRAF inhibitor vemurafenib in advanced melanoma with a BRAF V600 mutation. The combination delays the development of resistance compared with BRAF inhibition alone.

Coccidioides immitis

Soil fungus from dry regions of the south-western USA and Mexico. Inhaled spores cause valley fever, usually as a flu-like lung infection, rarely spreading to the skin, bones or meninges.

Cochlear duct

Endolymph-filled membranous duct of the cochlea in the inner ear, on whose basilar membrane the organ of Corti sits.

Cochlear implant

Electronic hearing prosthesis that directly stimulates the auditory nerve in severe to profound hearing loss.

Cochrane

International network that produces systematic reviews of medical treatments, pooling the evidence for decisions. Its reviews are regarded as an important foundation of evidence-based medicine.

Cockayne syndrome

Rare inherited disorder of DNA repair with growth failure, signs of premature ageing, light-sensitive skin and progressive neurological deficits. Unlike xeroderma pigmentosum, the risk of skin cancer is not increased.

Cockcroft-Gault formula

Older formula for estimating creatinine clearance from age, body weight, sex and serum creatinine. It is still widely used for adjusting drug doses in reduced kidney function.

Codeine

Weak opioid for dry cough and moderate pain that is partly converted to morphine in the liver by the enzyme CYP2D6. In ultra-rapid metabolisers overdose can occur, so it is not suitable for children under 12 or during breastfeeding.

Codman triangle

Triangular lifting of the periosteum at the edge of a bone tumour on X-ray. It indicates rapid, aggressive growth, for example in osteosarcoma, but can also occur in infections.

Codon

Sequence of three bases in mRNA that, in protein synthesis, stands for a particular amino acid or a start or stop signal. The genetic code comprises 64 codons.

Coenzyme Q10

Substance made by the body for energy production in the mitochondria; its benefit as a dietary supplement is not proven for most uses.

Coffin-Lowry syndrome

Rare X-linked inherited disease with intellectual disability, typical facial features, soft hands with tapering fingers and skeletal changes. Boys are usually more severely affected than girls.

Coffin-Siris syndrome

Rare genetic developmental disorder usually caused by changes in genes of the SWI/SNF chromatin complex. Characteristic features are underdeveloped tips or nails, especially of the fifth finger, coarse facial features and developmental delay.

Cogan syndrome

Rare inflammatory vascular disease, mainly in young adults, that attacks the cornea and inner ear. Typical features are red, light-sensitive eyes, hearing loss, tinnitus and vertigo.

Cognard classification

Detailed classification of dural arteriovenous fistulas into types I to V according to drainage direction, involvement of cortical veins and venous dilation. Higher types are associated with more bleeding and neurological deficits.

Cohen syndrome

Rare autosomal recessive inherited disease with developmental delay, low muscle tone, short-sightedness with retinal degeneration, neutropenia and typical facial features. It is caused by mutations in the VPS13B gene.

Colchicine

Anti-inflammatory plant-derived drug used in acute gout attacks, familial Mediterranean fever and pericarditis. Because of its narrow therapeutic range, accurate dosing is important.

Colecalciferol

Vitamin D3, used to prevent and treat vitamin D deficiency and to prevent rickets in infants. It is converted to the active form in the liver and kidney; long-term overdose can raise calcium levels dangerously.

Colesevelam

Bile acid sequestrant that binds bile acids in the gut and thus lowers cholesterol levels. It is also used for bile acid diarrhoea and can impair the absorption of other drugs.

Colestipol

Bile acid sequestrant that binds bile acids in the gut and thus lowers LDL cholesterol. Typical side effects are constipation and bloating; other drugs may be absorbed less well.

Colestyramine

Ion-exchange resin that binds bile acids in the gut and thus lowers LDL cholesterol. It is also used against itching in cholestasis and for bile acid diarrhoea and can interfere with the absorption of other drugs.

Colistin

Old antibiotic from the polymyxin group that destroys the outer membrane of Gram-negative bacteria. Today it is used as a reserve drug against multidrug-resistant pathogens; kidney and nerve damage are possible.

Colles’ fracture

Most common distal radius fracture near the wrist, in which the distal fragment tilts towards the back of the hand, typically after a fall on the outstretched hand. Older people with osteoporosis are often affected.

Colorado tick fever

Tick-borne viral disease in the Rocky Mountains with fever, headache and muscle pain, often in two bouts of fever. It usually runs without complications.

Colorectal cancer

Malignant tumour of the colon or rectum that usually develops from initially benign polyps. Colonoscopy allows early detection and the removal of precursors.

Common bile duct

Main bile duct that carries bile from the liver and gallbladder to the duodenum, where it usually opens together with the pancreatic duct. Gallstones can block it and cause jaundice.

Common hepatic duct

Duct formed by the joining of the right and left hepatic ducts, which becomes the common bile duct after the cystic duct joins it.

Commotio cordis

Sudden ventricular fibrillation caused by a blunt blow to the chest, for example by a ball striking during a particular phase of the cardiac cycle. Rapid resuscitation and defibrillation are crucial.

Commotio retinae

Temporary whitish clouding of the retina after blunt eye trauma that reduces vision if the macula is affected. It usually resolves within weeks.

Community health nurse

Nurse with a master’s degree who takes on health promotion, counselling and coordination in community-based care. In Germany the concept is being tested in pilot projects.

Compassionate use

Programme in which a not-yet-approved medicine is made available in a controlled way to seriously ill patients with no other treatment options. In Germany this is governed by a specific ordinance on hardship cases.

Computed tomography (CT)

Imaging technique that uses X-rays to produce cross-sectional images of the body. It is fast and particularly suitable for bones, lungs and emergencies.

Concha bullosa

Air-filled enlargement of the middle nasal turbinate, a common anatomical variant. If large, it can obstruct nasal breathing and impair sinus drainage.

Concizumab

Monoclonal antibody against tissue factor pathway inhibitor (TFPI) that strengthens blood clotting via the extrinsic pathway. It is injected daily under the skin to prevent bleeding in haemophilia with inhibitors.

Cone beam CT (digital volume tomography)

Three-dimensional X-ray technique for the jaws and facial skeleton with lower radiation than conventional CT. It is used, for example, before implant placement or for impacted teeth.

Confluence of sinuses

Meeting point of several venous sinuses of the dura mater at the internal occipital protuberance. From here, blood drains via the transverse sinuses towards the neck veins.

Confounder

Variable linked both to the cause being studied and to the outcome, which can create or hide an apparent association. Observational studies are particularly susceptible.

Conivaptan

Intravenous vasopressin receptor antagonist that promotes the excretion of free water and is used in hyponatraemia. Too rapid a rise in sodium must be avoided because of the risk of osmotic demyelination.

Conn’s syndrome

Primary hyperaldosteronism, in which the adrenal cortex produces too much aldosterone because of a benign nodule or enlargement of both glands. It causes high blood pressure and sometimes low potassium and is one of the most common treatable causes of hypertension.

Conradi-Hünermann syndrome

X-linked dominant form of chondrodysplasia punctata that affects almost only girls. Typical features are punctate calcifications of cartilage in infancy, streaky skin changes along the lines of Blaschko, unequal leg lengths and cataract.

CONSORT

Internationally recognised checklist for the complete and transparent reporting of randomised controlled trials. Many journals require authors to follow it.

Constant-Murley score

Score of shoulder function (0 to 100 points) based on pain, daily activities, range of motion and strength. It is a standard in shoulder surgery.

Contezolid

Antibiotic from the oxazolidinone group, similar to linezolid, possibly with lower bone marrow toxicity. It is approved in China for skin and soft tissue infections.

Continuous training method

Endurance training method in which a load is maintained without a break for a longer period, usually at low to moderate intensity. It mainly improves basic endurance and fat metabolism.

Contraceptive injection (three-monthly)

Hormonal contraception with a progestogen depot injected into the muscle or under the skin every twelve weeks. It is very reliable but can cause cycle irregularities and, with long-term use, loss of bone density.

Conus elasticus

Elastic membrane between the cricoid cartilage and the vocal cord, whose upper edge forms the vocal ligament. Cricothyrotomy is performed through its front part.

Conus medullaris

Cone-shaped lower end of the spinal cord, in adults at about the level of the first to second lumbar vertebra. Damage causes problems with bladder, bowel and sexual function.

Conus medullaris syndrome

Damage to the lower end of the spinal cord with saddle-area sensory loss and bladder, bowel and sexual dysfunction, with leg strength usually preserved. Causes include tumours, disc herniations or injuries.

Cool-down

Calm closing phase after training, such as gentle jogging, intended to ease the transition to recovery. According to studies so far, it does not reliably prevent muscle soreness.

Coombs test

Laboratory test that detects antibodies on red blood cells or in the serum. It is used when autoimmune anaemia, transfusion reactions are suspected, and in pregnancy.

Cooper’s ligaments

Fine connective tissue strands that connect the breast gland to the skin and the fascia of the chest muscle and give it support. If a tumour pulls on them, skin dimpling can result.

COPD

Chronic obstructive pulmonary disease: permanent narrowing of the airways, usually due to many years of smoking. Typical features are cough, sputum and increasing breathlessness.

In depth: COPD →

Copeptin

Stable fragment released together with antidiuretic hormone that reflects its secretion. It is used to investigate diabetes insipidus and can additionally help rule out a heart attack.

Coping

All the strategies a person uses to deal with strain and stress, for example problem-focused or emotion-focused. Helpful strategies can be practised in psychotherapy.

Cor pulmonale

Strain and enlargement of the right ventricle due to lung disease or pulmonary hypertension. Typical causes are COPD, pulmonary embolism and pulmonary fibrosis; leg swelling and breathlessness are common signs.

Cori cycle

Metabolic cycle in which lactate from working muscles or red blood cells travels to the liver and is rebuilt into glucose there. The glucose can then be used again by the muscle.

Cori disease

Glycogen storage disease type III due to deficiency of the glycogen debranching enzyme, affecting the liver and often also muscles and heart. Typical features are low blood sugar, liver enlargement and, over time, muscle weakness.

Cormack-Lehane classification

Grading of the view of the larynx during direct laryngoscopy into four grades, from a fully visible glottis to a non-visible epiglottis. Higher grades indicate a difficult intubation.

Cornelia de Lange syndrome

Congenital malformation syndrome with growth delay, intellectual disability, eyebrows that meet in the middle, long eyelashes and often malformations of the hands and arms. It is usually caused by a new mutation in the NIPBL gene.

Cornell criteria

ECG criterion for thickening of the left ventricle: the sum of the R wave in aVL and the S wave in V3, abnormal from 28 mm in men and 20 mm in women.

Cornell Scale for Depression in Dementia

Observer-rated scale for assessing depressive symptoms in people with dementia that combines information from carers with the clinician’s own observation.

Corona mortis

Common vascular connection between the external iliac vessels and the obturator vessels that runs over the superior pubic ramus. Injury to it during pelvic fractures or groin hernia surgery can cause heavy bleeding.

Corona radiata

Fan-shaped spread of nerve fibres between the cerebral cortex and the internal capsule. Small infarcts in this area can cause paralysis or sensory loss on one side of the body.

Corpus albicans

Whitish connective tissue scar in the ovary that forms when a corpus luteum regresses without pregnancy. It is gradually broken down over time.

Corpus callosum

Broad band of nerve fibres that connects the two cerebral hemispheres and allows them to exchange information.

Corpus cavernosum recti

Arterially supplied vascular cushion above the dentate line that contributes to the fine closure of the anus. When these cushions enlarge, they are called haemorrhoids.

Corpus spongiosum

Spongy erectile body of the penis that surrounds the urethra and continues into the glans. It fills less firmly than the corpora cavernosa during erection so that the urethra stays open.

Cortisol

Stress hormone of the adrenal cortex that influences metabolism, blood sugar and the immune system and dampens inflammation.

Corynebacterium diphtheriae

Bacterium whose toxin-producing strains cause diphtheria. The toxin damages the throat lining, heart and nerves; vaccination is directed against this toxin.

Costello syndrome

Rare RASopathy caused by mutations in the HRAS gene, with failure to thrive, loose skin, heart defects and an increased risk of childhood tumours. It resembles Noonan syndrome.

Cotard’s syndrome

Rare nihilistic delusion in which people are convinced that they are dead, do not exist or have lost organs. It occurs mainly in severe depression and psychoses.

Cottle test

Examination in which the cheek is pulled sideways to widen the nasal valve. If nasal breathing improves, this suggests narrowing at the internal nasal valve.

Cotton wool spots

Soft, whitish, fluffy patches in the retina. They result from small infarcts of the nerve fibre layer, for example in high blood pressure, diabetes or HIV.

Couplet

Two consecutive extrasystoles. When several extrasystoles occur in a row, this is called a salvo; frequent ones can indicate heart disease.

Courvoisier’s sign

Painless, palpable, distended gallbladder together with jaundice. It points to a slowly developing blockage of the bile duct, often due to a tumour in the head of the pancreas.

Cover test

Test in which one eye at a time is covered while watching for refixation movements of the other. It detects manifest and latent squint.

COVID-19

Disease caused by the coronavirus SARS-CoV-2, ranging from mild cold-like symptoms to severe pneumonia.

Cowden syndrome

Inherited tumour predisposition syndrome caused by mutations in the PTEN gene, with benign overgrowths (hamartomas) of the skin, mucosa and gut. There is an increased risk of breast, thyroid and uterine cancer, so regular screening is recommended.

Cowper’s gland

Paired, pea-sized gland below the prostate that releases a clear, mucous secretion (pre-ejaculate) into the urethra during sexual arousal. It neutralises urine residues and eases sperm transport.

COWS scale

Clinical Opiate Withdrawal Scale with eleven items such as pulse, sweating, pupil size, yawning and restlessness for assessing the severity of opioid withdrawal. It helps time the start of substitution, for example with buprenorphine.

Cox regression

Statistical model for survival data that estimates the influence of several factors simultaneously on the risk of an event. The result is usually a hazard ratio for each factor.

Coxa valga

Increased angle between the neck and shaft of the femur, which places unfavourable load on the hip socket. It often occurs in hip dysplasia or neuromuscular diseases and can contribute to hip osteoarthritis.

Coxa vara

Reduced angle between the neck and shaft of the femur, which can shorten the leg and disturb the gait. It can be congenital or result from disease or injury.

Coxiella burnetii

Intracellular bacterium transmitted mainly from sheep and goats via dust. It causes Q fever and can cause chronic infections, for example of heart valves.

Coxsackieviruses

Subgroup of enteroviruses that cause hand, foot and mouth disease, herpangina and feverish infections, mainly in children. Less often, they cause inflammation of the heart muscle or meninges.

CPAP

Breathing therapy with continuous positive pressure via a mask that keeps the upper airways open. It is the standard treatment for obstructive sleep apnoea.

CPOT

Critical-Care Pain Observation Tool, an observational instrument for assessing pain in intensive care patients who cannot communicate. It rates facial expression, body movements, muscle tension and ventilator compliance or vocalisation.

Cranberry

North American berry whose constituents may make it harder for certain bacteria to stick to the bladder wall. The evidence for preventing cystitis is mixed, and it is not suitable for treatment.

Craving

Strong, hard-to-control desire for an addictive substance or behaviour. It is a core feature of dependence and a frequent trigger of relapse.

Crazy paving

CT pattern of ground-glass opacity with superimposed thickened septal lines resembling irregular paving stones. It is classic in pulmonary alveolar proteinosis but also occurs in pneumonias such as COVID-19.

Cream

Spreadable preparation of fat and water that is absorbed more easily than an ointment. Depending on its fat and water content, it suits different skin types.

Credé manoeuvre

Manoeuvre to detach and deliver the placenta by firm pressure on the fundus of the uterus. It is used only when delivery of the placenta is delayed and with caution.

Credé prophylaxis

Formerly routine administration of eye drops to newborns to prevent gonococcal conjunctivitis. In Germany it is no longer performed routinely because maternal infections are detected and treated beforehand.

Creutzfeldt-Jakob disease

Rare, fatal brain disease caused by misfolded proteins (prions), usually occurring spontaneously. It is marked by rapidly progressive dementia with muscle jerks and gait problems; there is no causal treatment.

Cri du chat syndrome

Rare chromosomal disorder with a missing piece of chromosome 5, a cat-like cry in infancy and developmental delay.

Crigler-Najjar syndrome

Rare inherited liver enzyme defect in which bilirubin can hardly be conjugated with glucuronic acid. In severe type 1, kernicterus can occur in newborns; type 2 responds to phenobarbital.

Crinecerfont

Drug that blocks the CRF1 receptor in the pituitary gland and so reduces the excessive ACTH and androgen production in congenital adrenal hyperplasia. As a result, the glucocorticoid dose can be reduced in many patients.

CRISPR-Cas9

Molecular tool (“gene scissors”) that can cut and modify DNA at a precisely defined site. It is used in research and increasingly in gene therapies.

Crista galli

Cock’s-comb-shaped bony projection of the ethmoid bone in the anterior cranial fossa to which the falx cerebri is attached. It is a landmark of the skull base on CT images.

Crista terminalis

Muscular ridge on the inner wall of the right atrium that separates the smooth from the trabeculated part of the atrium. It is a common site of origin of focal atrial tachycardias.

Critical Incident Reporting System (CIRS)

Anonymous reporting system in which staff report critical events and near misses so that causes can be analysed and processes improved. It is a tool of clinical risk management.

Crizanlizumab

Antibody against P-selectin that was intended to reduce pain crises in sickle cell disease. The EU revoked its conditional authorisation in 2023 because a confirmatory study showed no benefit.

Crizotinib

Tablet that inhibits the kinases ALK and ROS1 and is used in non-small cell lung cancer with the corresponding genetic change. Transient visual disturbances, nausea, oedema and raised liver values are common.

Cromoglicic acid (cromolyn)

Mast cell stabiliser that preventively relieves allergic symptoms as eye drops or nasal spray. The full effect develops only after a few days of regular use; it is very well tolerated.

Cronbach’s alpha

Measure of the internal consistency of a questionnaire or scale, i.e. how well the individual questions measure the same construct. Values of about 0.7 or more are usually considered acceptable; very high values may point to redundant questions.

Cronkhite-Canada syndrome

Very rare, non-inherited disease with numerous polyps in the stomach and intestine, diarrhoea, protein loss, hair loss, nail changes and skin pigmentation. The cause is unclear; treatment includes corticosteroids and nutritional therapy.

Crossectomy (high ligation)

Varicose vein operation in which the main superficial vein is tied off and divided where it joins the deep vein at the groin or back of the knee. It is often combined with stripping of the vein; endovenous procedures are an alternative.

Crossover trial

Study design in which all participants receive both treatments one after the other in random order, so that each serves as their own control.

Crotamiton

Topical agent against scabies mites that also relieves itching. It is considered less effective than permethrin and is mainly considered as an alternative in infants and in pregnancy.

Crouzon syndrome

Inherited craniosynostosis with premature closure of the skull sutures, a flat midface and bulging eyes. It is usually caused by variants in the FGFR2 gene; operations to relieve pressure on the skull are often needed.

Crovalimab

Monoclonal C5 antibody injected under the skin every four weeks after a loading phase in paroxysmal nocturnal haemoglobinuria. Like other complement inhibitors, it requires vaccination against meningococci.

Crowe classification

Classification of hip dysplasia in adults according to how far the femoral head is displaced upwards out of the socket (types I to IV). It is important for planning a hip replacement.

Crush syndrome

Life-threatening consequence of prolonged crushing of large muscle groups, for example after being buried: after release, muscle breakdown products such as potassium and myoglobin enter the blood and can cause arrhythmias and kidney failure. Early fluid administration is crucial.

Cryopyrin-associated periodic syndrome

Rare inherited autoinflammatory disease caused by mutations in the NLRP3 gene, leading to episodes of fever, hive-like rash, joint and eye inflammation and sometimes hearing loss. Interleukin-1 blockers work well.

Cryptococcus neoformans

Encapsulated yeast found in bird droppings and soil. In severe immunodeficiency, such as advanced HIV infection, it causes dangerous meningitis.

CTCAE

Standardised criteria of the US National Cancer Institute for grading adverse events from grade 1 (mild) to 5 (fatal). They are used in cancer trials and clinical practice for consistent documentation.

Cuff pressure measurement

Checking the pressure in the cuff of an endotracheal tube or tracheostomy tube with a manometer. Too high a pressure damages the tracheal lining, too low a pressure favours aspiration.

Cullen’s sign

Bluish discolouration of the skin around the navel due to blood in the abdominal or retroperitoneal space. It occurs, for example, in severe pancreatitis or ruptured ectopic pregnancy and is a warning sign.

Cuneus

Wedge-shaped cortical area on the inner surface of the occipital lobe above the calcarine sulcus. It processes visual input from the lower half of the visual field.

Cupula (inner ear)

Gelatinous cap in the widened end of each semicircular canal that is deflected by endolymph during head rotation and thus stimulates the sensory cells.

CURB-65

Simple score to assess the severity of community-acquired pneumonia based on confusion, urea, respiratory rate, blood pressure and age 65 or over. Without a laboratory value, the CRB-65 variant is used.

Currarino syndrome

Congenital combination of a sacral malformation, a malformation of the rectum or anus and a mass in front of the sacrum. It often presents with persistent constipation in childhood.

Cushing reflex

The body’s response to severely raised intracranial pressure, with rising blood pressure, slowed pulse and irregular breathing. This combination is an alarm sign of impending brainstem herniation.

Cushing’s syndrome

Condition caused by excess cortisol, for example from long-term corticosteroid use, with weight gain around the trunk and a rounded “moon face”.

Cutibacterium acnes

Skin bacterium that lives in sebaceous follicles and is involved in acne inflammation. It can also cause infections of implants such as shoulder prostheses; formerly called Propionibacterium acnes.

Cutis laxa

Inherited or acquired disease with loose, wrinkled skin due to defective elastic fibres. In some forms, the lungs, blood vessels or bowel are also affected.

Cutis marmorata

Net-like, bluish marbled skin pattern caused by vascular reactions to cold, which is common and harmless in infants. If it persists, the cause should be investigated.

Cyberbullying

Bullying via digital media such as social networks or messaging apps, which can act around the clock and in front of a large audience. Content should be saved, perpetrators blocked and trusted persons or counselling services involved.

Cyclopentolate

Eye drops that dilate the pupil and temporarily paralyse accommodation. They are used mainly in children to measure refractive errors objectively.

Cyclophosphamide

Alkylating cytostatic and immunosuppressant that is activated in the liver. It is used to treat lymphomas, breast cancer and severe autoimmune diseases; breakdown products can irritate the bladder, which mesna protects against.

Cyclosporiasis

Intestinal infection with the parasite Cyclospora cayetanensis, usually via contaminated fruit, vegetables or water. It causes prolonged watery diarrhoea and is treated with co-trimoxazole.

CYFRA 21-1

Tumour marker made of fragments of the cytoskeletal protein cytokeratin 19. It is used mainly to monitor non-small cell lung cancer, not for screening.

CYP2D6

Liver enzyme that breaks down or activates numerous drugs such as antidepressants, beta blockers, tamoxifen and codeine. Inherited differences mean that some people metabolise drugs very slowly or very quickly.

Cyproheptadine

Older antihistamine with additional serotonin-blocking activity. It is occasionally used in serotonin syndrome and often increases appetite.

Cyproterone acetate

Progestogen with a strong anti-androgenic effect, used for marked virilisation in women, severe acne or hirsutism and in prostate cancer. Because of a dose-dependent risk of meningioma, use of higher doses has been restricted.

Cystatin C

Blood protein that indicates kidney function independently of muscle mass.

Cystic duct

Duct that connects the gallbladder to the common bile duct. A gallstone lodged here can cause biliary colic or cholecystitis.

Cystine crystals

Colourless, hexagonal crystals in the urine. Their detection proves cystinuria, an inherited disorder with recurrent kidney stones.

Cystoisosporiasis

Intestinal infection with the protozoan Cystoisospora belli. It causes watery diarrhoea that can be prolonged in people with HIV and is treated with co-trimoxazole.

Cytarabine

Antimetabolite cytostatic drug that disrupts the incorporation of DNA building blocks and is a mainstay of treatment for acute myeloid leukaemia. At high doses it can cause cerebellar problems and conjunctivitis, so corticosteroid eye drops are given preventively.

Cytisine

Plant-derived substance from laburnum that, like varenicline, acts on nicotine receptors and supports smoking cessation. It is inexpensive and effective in studies but should only be taken at the intended dose.

Cytochrome P450 enzymes

Family of enzymes, mainly in the liver, that break down many drugs. Inhibition or induction of these enzymes is a common cause of drug interactions.

Back to the Medical Encyclopedia overview

Medical Encyclopedia: C

Caecum

Care directive (guardianship preference)

Care needs assessment tool (Germany)

Carotid artery

Central retinal artery

Cerebral aqueduct

Chest compress

Chest pain

Chorioamnionitis

Choroid

Choroidal melanoma

Choroidal naevus

Chronic exertional compartment syndrome

Circum-rescue collapse

Circumflex scapular artery

Clinical block placement

Co-payment limit (Germany)

Coarctation of the aorta

Comfrey

Common hepatic artery

Common iliac artery

Common interosseous artery

Complementary feeding

Computer glasses

Conditional marketing authorisation

Congenital adrenal hyperplasia

Congenital heart defect

Conjunctiva

Connective tissue

Connective tissue graft

Connective tissue weakness

Contraceptive pill

Controlled drug documentation

Controlled drugs (narcotics)

Counselling for relatives

Cystic artery

Cystitis

c-ANCA

C-peptide

C-reactive protein (CRP)

C1 esterase inhibitor

C3 glomerulopathy

CA 125

CA 15-3

CA 19-9

CA 72-4

Cabazitaxel

Cabergoline

Cabot rings

Cabotegravir

Cabozantinib

CAD/CAM dental restorations

CADASIL

Caeruloplasmin

Café-au-lait spot

Cafedrine

Caffey disease

CAGE questionnaire

Cagrilintide

Cairo classification

Calcidiol

Calcifediol

Calcinosis cutis

Calciphylaxis

Calcipotriol

Calcitonin

Calcitriol

Calcium

Calcium hydroxide (dentistry)

Calcium oxalate

Calming full-body wash

Calmodulin

Calot’s triangle

Calprotectin

CALR mutation

CAM-ICU

Cam impingement

Cameron lesions

Camizestrant