Medical Encyclopedia D: Medical Terms Explained

Dark circles under the eyes

Dark shadows under the eyes caused by thin skin, pigment, blood vessels or loss of volume.

Deep brachial artery

The artery that runs with the radial nerve around the humerus and supplies the triceps. In fractures of the humeral shaft it can be injured together with the nerve.

Deep femoral artery

The main branch of the femoral artery, supplying the thigh muscles and the femoral head. When the superficial femoral artery is blocked, it serves as an important collateral circulation.

Deep inguinal ring

The inner opening in the transversalis fascia through which the spermatic cord or round ligament enters the inguinal canal. Indirect inguinal hernias begin here.

Deep palmar arch

A deep arterial arch in the palm, fed mainly by the radial artery. It connects with the superficial arch, securing the blood supply to the hand.

Deep plantar arch

An arterial arch in the sole of the foot formed by the lateral plantar artery and a branch of the dorsalis pedis artery. The toe arteries arise from it.

Defence mechanisms

Mostly unconscious psychological strategies people use to protect themselves from distressing feelings, conflicts or fears, such as repression, projection or rationalisation. They are normal but in rigid form can maintain problems.

Delusion of reference

The delusional conviction that everyday events, gestures or media reports refer to oneself. It is common in schizophrenia.

Dental articulator

A mechanical device that holds models of the upper and lower jaw and imitates jaw movements. Dental technicians use it to make dentures with correct contacts.

Dental bonus booklet (Germany)

A booklet in which annual dental check-ups are recorded. In Germany, complete entries increase the health insurance subsidy for dentures.

Dental impression

Making an exact negative mould of the teeth and jaw with impression materials or digitally, as the basis for crowns, bridges, dentures or braces. Intraoral scanners increasingly replace conventional impressions.

Dental occlusion (bite)

The relationship between the upper and lower rows of teeth when biting together. Deviations such as overbite, underbite, crossbite or open bite are assessed in orthodontics and can affect chewing, speech and the jaw joints.

Descending genicular artery

A branch of the femoral artery in the adductor canal that contributes to the vascular network around the knee. Its skin branch accompanies the saphenous nerve to the inner side of the lower leg.

Descending pain inhibition

A nerve system running from the brainstem to the spinal cord that dampens pain signals via messengers such as serotonin, noradrenaline and the body’s own opioids. Some painkillers and antidepressants strengthen this inhibition.

Descending palatine artery

A branch of the maxillary artery in the pterygopalatine fossa that descends to the palate and, as the greater palatine artery, supplies the hard palate.

Diagnosis of exclusion

A diagnosis made only after other diseases with similar symptoms have been ruled out by investigations. Examples are irritable bowel syndrome and some headache types.

Dietary fibre

Indigestible plant components that support digestion, keep you full for longer and dampen rises in blood sugar. At least 30 g per day is recommended for adults.

Disc protrusion

A bulging of the intervertebral disc beyond the edge of the vertebral body with the outer fibrous ring still intact. It is often an incidental finding without symptoms but can press on nerve roots.

Discharge letter

A written report to the doctors continuing treatment, for example after a hospital stay, with diagnoses, findings, treatment and recommendations. It ensures information is passed on between care settings.

Doctor-patient communication

Communication between healthcare professionals and patients, for example in history-taking, informed consent and breaking bad news. Good communication demonstrably improves understanding, adherence and satisfaction and is taught in medical school.

Dorsal nasal artery

A terminal branch of the ophthalmic artery that emerges at the inner corner of the eye and supplies the bridge of the nose. Through connections with the angular artery it links the internal and external carotid systems, so nose fillers carry a risk of vascular occlusion.

Dorsalis pedis artery

The artery on the top of the foot whose pulse can be felt between the first and second metatarsal bones. A missing pulse may indicate peripheral arterial disease.

Drug eruption

A skin rash as a reaction to a medicine, often as measles-like red spots a few days after starting it. It is usually harmless; mucous membrane involvement or blisters are warning signs.

Drug tolerance

Declining effect of a medicine with repeated use, so that higher doses are needed for the same effect. It occurs, for example, with opioids, benzodiazepines and nitrates and must be distinguished from dependence.

Dry socket (alveolar osteitis)

A painful healing disorder after tooth extraction in which the blood clot in the socket is missing or breaks down. Severe pain from the second to fourth day is typical; smoking increases the risk.

D’Amico classification

Classification of localised prostate cancer into low, intermediate and high risk of recurrence according to PSA level, Gleason score and clinical T stage. It forms the basis of recommendations such as active surveillance, surgery or radiotherapy.

D cells (delta cells)

Hormone-producing cells in the stomach, intestine and pancreas that release somatostatin. Somatostatin inhibits the release of numerous other hormones and digestive juices.

D-dimer

Breakdown products of blood clots. Normal levels make deep vein thrombosis or pulmonary embolism unlikely.

D-mannose

Simple sugar offered as a dietary supplement to prevent recurrent cystitis. It is supposed to make it harder for E. coli to attach to the bladder wall; larger studies have so far shown no definite benefit.

Dabigatran

Oral direct thrombin inhibitor used to prevent stroke in atrial fibrillation and in thrombosis. A specific reversal agent is available for emergencies.

Dabrafenib

Inhibitor of the mutated BRAF protein used together with trametinib in BRAF V600-mutated melanoma and lung cancer. Fever is a typical side effect that can lead to a treatment pause.

Dacarbazine

Alkylating cytostatic drug, part of the ABVD regimen for Hodgkin lymphoma and formerly standard in metastatic melanoma. It causes severe nausea and is light-sensitive.

Dacomitinib

Second-generation irreversible EGFR inhibitor for lung cancer with an activating EGFR mutation. Rash and diarrhoea are common.

Dacrocytes (teardrop cells)

Teardrop-shaped red blood cells typical of bone marrow fibrosis. They form when cells squeeze through altered bone marrow.

Dacryoadenitis

Inflammation of the lacrimal gland with swelling and pain at the outer upper eyelid, giving the lid an S-shaped contour. Causes include viral infections, bacteria or inflammatory systemic diseases.

Dacryocystitis

Inflammation of the tear sac in the inner corner of the eye, usually with a narrowed tear duct, with redness, swelling and pus discharge.

Dalbavancin

Long-acting glycopeptide antibiotic against Gram-positive bacteria including MRSA. Because of its very long half-life, one or two infusions are often sufficient for a course of treatment.

Dalrymple’s sign

Visible white of the sclera above the cornea when looking straight ahead, due to a retracted upper eyelid. It is a common sign of thyroid eye disease.

Dalteparin

Low-molecular-weight heparin injected under the skin to prevent or treat thrombosis. Caution is needed in reduced kidney function.

DALY

Disability-adjusted life years: measure of disease burden that combines years of life lost through premature death and years lived with illness or disability. It is used in health reporting.

Damage control resuscitation

Treatment strategy for severely bleeding injured patients with early haemorrhage control, administration of blood products in a fixed ratio and limited infusion volume. It aims to prevent coagulopathy, hypothermia and acidosis.

Damage control surgery

Strategy in severely injured patients in which only bleeding and contamination are controlled quickly at first, with definitive repair after stabilisation. This aims to prevent hypothermia, coagulopathy and acidosis.

Danaparoid

Heparinoid anticoagulant that can be used in heparin-induced thrombocytopenia. It is injected under the skin or into a vein.

Dandy-Walker malformation

Congenital malformation of the cerebellum with an absent or reduced cerebellar vermis and a cystically enlarged fourth ventricle. Hydrocephalus often develops; children’s development varies widely.

Danicopan

Oral factor D inhibitor given in addition to a C5 inhibitor in paroxysmal nocturnal haemoglobinuria when extravascular haemolysis persists.

Danon disease

X-linked storage disease due to LAMP2 deficiency that mainly causes severe hypertrophic heart muscle disease, muscle weakness and sometimes intellectual impairment. Men develop the disease earlier and more severely.

Dantrolene

Muscle relaxant that inhibits calcium release in skeletal muscle. It is the life-saving antidote in malignant hyperthermia and is therefore kept available in every anaesthesia area.

Danuglipron

Oral, non-peptide GLP-1 receptor agonist whose development was stopped in 2025 because of liver injury in a study.

Dapagliflozin

SGLT2 inhibitor used to treat type 2 diabetes, heart failure and chronic kidney disease. It slightly lowers blood sugar and weight and protects the heart and kidneys.

Dapoxetine

Short-acting selective serotonin reuptake inhibitor taken as needed one to three hours before intercourse for premature ejaculation. Possible side effects are nausea, dizziness and, rarely, fainting.

Daprodustat

Oral HIF prolyl hydroxylase inhibitor that stimulates the body’s own production of erythropoietin. It was developed to treat anaemia of kidney disease in dialysis patients.

Dapsone

Sulfone antibiotic used to treat leprosy and certain skin diseases such as dermatitis herpetiformis. It can damage haemoglobin (methaemoglobin formation) and cause haemolysis.

Daptomycin

Reserve antibiotic against Gram-positive bacteria, including MRSA and VRE, that destroys the bacterial cell membrane. It does not work in pneumonia because surfactant inactivates it; creatine kinase should be monitored.

Daratumumab

Antibody against CD38 on myeloma cells that is now an integral part of many treatment combinations in multiple myeloma. It can interfere with antibody screening before blood transfusions.

Darbepoetin alfa

Genetically engineered, longer-acting variant of the hormone erythropoietin that stimulates the production of red blood cells. It is used mainly for anaemia due to chronic kidney disease or chemotherapy.

Daridorexant

Sleeping medication from the orexin receptor antagonist group that dampens the wake-promoting orexin system rather than sedating the brain in general. It is approved for chronic insomnia in adults.

Darier disease

Autosomal dominant disorder of keratinisation (ATP2A2 gene) with brownish, rough, often foul-smelling papules on the chest, back, forehead and scalp. Heat, sweating and UV light worsen the skin.

Darier’s sign

Redness and wheal formation on a skin spot after rubbing because mast cells release histamine. It is typical of cutaneous mastocytosis.

Darifenacin

Antimuscarinic for overactive bladder that acts preferentially on the M3 receptors of the bladder muscle. Dry mouth and constipation are typical.

Dark adaptation

Adjustment of the eye to darkness through pupil dilation, switching from cone to rod vision and regeneration of visual pigment. Full sensitivity is reached only after about 30 minutes.

Darolutamide

Androgen receptor inhibitor for the treatment of prostate cancer, for example in combination with androgen deprivation and chemotherapy. It hardly enters the brain, which is intended to reduce central nervous side effects.

Darrach procedure

Removal of the ulnar head for painful changes of the distal radioulnar joint, for example in osteoarthritis or rheumatoid arthritis. It improves forearm rotation but can lead to instability of the ulnar stump.

Darunavir

HIV protease inhibitor given together with a booster such as ritonavir or cobicistat. It has a high barrier to resistance but numerous interactions with other drugs.

DAS28

Disease activity score for rheumatoid arthritis based on 28 examined joints that combines tender and swollen joints, an inflammation marker and the patient’s assessment. Values below 2.6 are considered remission.

Dasatinib

Tyrosine kinase inhibitor against the BCR-ABL protein in chronic myeloid leukaemia and Philadelphia-positive acute lymphoblastic leukaemia. Pleural effusions are a typical side effect.

DASH diet

Eating pattern rich in vegetables, fruit, whole grains and low-fat dairy and low in salt, red meat and sugar, originally studied to lower blood pressure. Studies show a moderate reduction in blood pressure.

DASH score

Disabilities of the Arm, Shoulder and Hand questionnaire with 30 questions on the function of the entire upper limb; the short form QuickDASH has eleven questions.

Data Safety Monitoring Board

Independent expert committee that reviews safety and interim data during a clinical trial. It can recommend stopping a trial early because of harm, clear superiority or futility.

Datopotamab deruxtecan

Antibody-drug conjugate directed against the surface protein TROP2 that delivers a cytotoxic agent specifically into tumour cells; used in breast and lung cancer, among others.

Daunorubicin

Anthracycline used in induction therapy of acute leukaemias, often together with cytarabine. For certain forms of acute myeloid leukaemia there is also a liposomal combination of both drugs; heart damage limits the total dose.

David procedure

Valve-sparing replacement of the aortic root in which the patient’s own aortic valve is sewn into a vascular graft. Long-term anticoagulation is usually not needed afterwards.

Dawn phenomenon

Rise in blood sugar in the early morning hours due to increased night-time release of hormones such as growth hormone and cortisol. In diabetes it may require adjustment of insulin therapy.

Dawson’s fingers

Elongated demyelinating lesions on MRI that lie perpendicular to the ventricles and project like fingers into the white matter. They are typical of multiple sclerosis.

De Clérambault’s syndrome (erotomania)

Delusional belief of being loved by a person, usually of higher status, who knows nothing about it. It occurs in psychoses and can lead to harassing behaviour.

De Ritis ratio

Ratio of the liver values AST to ALT. Values below 1 suggest mild liver cell damage as in viral hepatitis, values above 1 more severe damage, alcohol-related liver disease, cirrhosis or an origin in muscle or heart.

De Winter T waves

ECG pattern with upsloping ST depression at the J point and tall, symmetrical T waves in the chest leads. It is considered a heart attack equivalent in acute occlusion of the left anterior descending artery and requires immediate catheterisation.

Deamination

Removal of the amino group from amino acids, producing ammonia, which is detoxified in the liver via the urea cycle. The remaining carbon skeleton can be used for energy.

Deauville score

Five-point scale for assessing response of lymphomas to treatment on PET-CT, comparing the metabolic activity of residual findings with the mediastinum and liver. Scores of 1 to 3 are usually considered a good response.

DeBakey classification

Older classification of aortic dissection into types I to III according to the site of the tear and its extent. It complements the simpler Stanford classification.

Debridement

Removal of dead tissue, slough and foreign bodies from a wound, by surgical, mechanical, enzymatic or biological means. It creates the conditions for wound healing.

Debulking

Surgical tumour reduction in which as much tumour mass as possible is removed, even if complete removal is not possible. In ovarian cancer the goal is to leave no visible residual tumour.

Decidua

Lining of the uterus remodelled during pregnancy into which the embryo implants. It is shed after birth with the lochia.

Decitabine

Hypomethylating agent used in older patients with acute myeloid leukaemia or myelodysplastic syndrome. It reactivates silenced genes in tumour cells.

Declaration of Helsinki

Ethical principles for medical research involving human beings adopted by the World Medical Association in 1964 and revised several times. Key points are informed consent, weighing of benefits and risks, and ethics committees.

Décolleté wrinkles

Vertical wrinkles in the chest area favoured by side sleeping, UV damage and loss of elasticity. Consistent sun protection helps prevent them; aesthetic treatments are not well studied.

Decompensation

State in which an organ or system can no longer maintain its function despite compensatory mechanisms, for example decompensated heart failure.

Decompression sickness

Divers’ disease in which gas bubbles form in tissues and blood after surfacing too quickly. Symptoms range from joint pain to paralysis; treatment is with oxygen and a hyperbaric chamber.

Decontamination

Removal of hazardous substances such as chemicals or radioactive particles from skin, clothing and equipment. Simply removing clothing eliminates a large part of the contamination.

Default mode network

Network of brain regions active at rest, during mind-wandering and when thinking about oneself, including the precuneus and cingulate gyrus. Changes in this network are being studied in Alzheimer’s disease, depression and autism.

Defecation

Technical term for emptying the bowels, an interplay of bowel movement, sphincter muscles and pelvic floor.

Defecation reflex

Reflex sequence in which stretching of the rectum triggers the urge to defecate and relaxes the internal sphincter. The external sphincter remains under voluntary control, so emptying can be postponed.

Deferasirox

Oral iron chelator that binds excess iron and eliminates it via the stool, for example in patients receiving frequent blood transfusions for thalassaemia. Kidneys, liver and hearing are checked regularly during treatment.

Deferiprone

Oral iron chelator for the treatment of transfusion-related iron overload. Because it can rarely cause dangerous agranulocytosis, the blood count is checked regularly and fever is assessed by a doctor immediately.

Deferoxamine

Iron chelator that binds excess iron and eliminates it via urine and stool. It is given by infusion for iron overload due to frequent transfusions and in acute iron poisoning.

Defibrillation

Delivery of an electric shock across the heart to stop ventricular fibrillation or pulseless ventricular tachycardia. Automated external defibrillators allow lay people to use it safely during resuscitation.

Defibrillator

Device that delivers an electric shock in ventricular fibrillation to restore normal heart rhythm. Automated external defibrillators (AEDs) can also be used by lay people.

Defibrotide

Mixture of oligonucleotides with vessel-protecting and anticoagulant effects. It is used to treat severe veno-occlusive disease of the liver after stem cell transplantation; the main risk is bleeding.

Deflazacort

Glucocorticoid used in Duchenne muscular dystrophy to slow muscle loss. Compared with prednisone, slightly less weight gain but more frequent cataracts have been described.

Degarelix

GnRH antagonist for hormone therapy in advanced prostate cancer. It lowers testosterone rapidly without the initial hormone surge that can occur with GnRH agonists.

Degos disease

Malignant atrophic papulosis, a very rare vascular disease with porcelain-white, sunken skin papules with a red border. Possible vascular occlusions in the bowel or brain are problematic and can be life-threatening.

Dehydration

Lack of fluid in the body due to insufficient intake or losses through diarrhoea, vomiting or sweating. Infants and older people are particularly at risk.

Dehydration prevention

Measures to avoid fluid deficiency, especially in older people with a reduced sense of thirst. These include fixed drinking times, fluid charts and offering preferred drinks.

Dejerine-Roussy syndrome

Condition after damage to the thalamus, usually from a stroke. Typical features are sensory loss on the opposite side and later central pain that is difficult to treat.

Delafloxacin

Newer fluoroquinolone with extended activity against Gram-positive pathogens including MRSA. It is intended for skin and soft tissue infections and community-acquired pneumonia when other antibiotics are unsuitable.

Delamanid

Nitroimidazole antibiotic that inhibits the formation of mycolic acids in the cell wall of tuberculosis bacteria and is part of combination therapy for multidrug-resistant tuberculosis.

Delandistrogene moxeparvovec

Gene therapy for Duchenne muscular dystrophy that uses a viral vector to deliver a shortened form of dystrophin into the muscles. Its benefits and risks remain controversial.

Delayed pressure urticaria

Delayed, deep and painful swelling of the skin at sites of sustained pressure, for example under belts or bag straps or on the soles of the feet after long walks.

Deletion

Loss of a section of genetic material, ranging from a single base to large pieces of a chromosome. If important genes are missing as a result, diseases such as DiGeorge syndrome can arise.

Delgocitinib

Janus kinase inhibitor cream used to treat moderate to severe chronic hand eczema in adults when corticosteroid creams are not sufficient. Because it is applied topically, little active substance enters the blood.

Delirium

Acute confusion with disturbed attention and consciousness, often fluctuating over the day. It is common in older people after surgery or during infections.

Delirium management

Bundled measures for the prevention, early detection and treatment of delirium in hospital, such as orientation aids, promotion of sleep, early mobilisation and medication review. Structured programmes can reduce the frequency of delirium and complications.

Delirium prevention

Measures to prevent delirium in at-risk, usually older patients, such as orientation aids, glasses and hearing aids, promotion of sleep and early mobilisation.

Delirium screening

Regular testing for delirium with short instruments such as CAM-ICU or Nu-DESC. Because many cases of delirium are quiet, it helps detect them early and treat the causes.

Delirium tremens

Life-threatening withdrawal delirium that usually begins two to four days after stopping long-term heavy drinking. Typical features are confusion, hallucinations, tremor, sweating, racing heart and seizures; it requires intensive care treatment.

Deload week

Planned training week with reduced volume or intensity that serves recovery. It is intended to prevent overload and allow adaptation.

Delorme procedure

Transanal operation for rectal prolapse in which the mucosa of the prolapsed section is removed and the muscle wall is plicated. It is not very demanding for the patient but has a higher recurrence rate than abdominal procedures.

Delta-aminolevulinic acid

First building block of haem synthesis. Its excretion in urine rises in acute porphyrias and lead poisoning.

Delta gap

Comparison of the rise in the anion gap with the fall in blood bicarbonate. This helps identify mixed acid-base disorders, for example when bicarbonate is lost in addition to lactic acidosis.

Delta wave

Slowly rising start of the QRS complex on the ECG, caused by premature excitation of the ventricle via an accessory pathway. It is typical of Wolff-Parkinson-White syndrome.

Deltoid muscle

Triangular muscle that covers the shoulder and mainly lifts the arm sideways. It is also a common site for intramuscular injections such as vaccines.

Dementia

Umbrella term for the progressive loss of mental abilities such as memory, thinking and orientation that impairs daily life. The most common cause is Alzheimer’s disease.

In depth: Dementia →

Demodex mites

Tiny mites that live in the hair follicles and sebaceous glands of the face in almost all adults. In large numbers they are associated with blepharitis, rosacea and a scaly facial dermatitis.

Demodicosis

Skin changes caused by excessive multiplication of hair follicle mites, usually on the face. It resembles rosacea with redness and pustules and often responds to topical ivermectin.

DemTect

Short dementia screening test with a word list, number conversion, word fluency and memory tasks. It serves as a screening tool and does not replace detailed assessment.

Demyelination

Loss of the myelin sheath around nerve fibres, which slows or blocks nerve conduction. It occurs in multiple sclerosis, ADEM and certain polyneuropathies.

Dendritic cells

Immune cells that take up pathogens, break them down and present their fragments to T cells. They thus form the bridge between innate and adaptive immunity.

Dengue fever

Mosquito-borne viral disease in tropical regions with high fever, headache and aching limbs.

Dengue vaccination

Vaccination against dengue virus with a live attenuated vaccine. It is recommended mainly for people who have already had a dengue infection, because second infections can be more severe.

Denis classification

Model that divides the spine into anterior, middle and posterior columns; a fracture is considered unstable if at least two columns are affected. The same name is also used for a classification of sacral fractures.

Dennie-Morgan fold

Double fold of skin below the lower eyelid that occurs more often in people with an atopic predisposition such as atopic eczema. It is a minor sign of atopy, not proof.

Denosumab

Monoclonal antibody that inhibits bone breakdown and is injected under the skin every six months in osteoporosis. Follow-on treatment is needed after stopping, otherwise vertebral fractures can increase.

Dens evaginatus

Cusp-like projection on the chewing surface or inner side of a tooth that often contains an extension of the pulp. If it breaks off, the tooth nerve can die, so it is protected preventively or gradually reduced.

Dens invaginatus

Developmental anomaly in which enamel folds into the interior of the tooth, usually in upper lateral incisors. Bacteria can easily reach the pulp via the invagination, so early sealing is recommended.

Dens (odontoid process)

Tooth-shaped bony peg of the second cervical vertebra around which the first cervical vertebra rotates when the head is turned. Fractures of the dens occur mainly in older people after falls.

Dense deposit disease

Subtype of C3 glomerulopathy with ribbon-like, electron-dense deposits in the glomerular basement membrane. It is caused by dysregulation of the alternative complement pathway and often affects children and young adults.

Dent disease

X-linked disorder of the proximal renal tubule with loss of small proteins and calcium in the urine, kidney stones and kidney calcification. In affected men it can slowly progress to kidney failure.

Dental fluorosis

Whitish to brownish spots in tooth enamel caused by excessive fluoride intake during tooth development. It is usually an aesthetic problem.

Dental hygienist

Dental professional with advanced training or a degree who performs professional tooth cleaning, periodontal maintenance and preventive advice.

Dentine

Bone-like hard tissue that forms the bulk of the tooth and lies beneath the enamel and root cementum. It contains fine tubules through which stimuli reach the pulp; exposed dentine causes sensitive tooth necks.

Dentine hypersensitivity

Short, sharp tooth pain with cold, sweet foods or touch because exposed dentine transmits stimuli to the nerve. Causes include gum recession or loss of enamel; special toothpastes and varnishes can help.

Dentinogenesis imperfecta

Inherited malformation of the dentine that leads to brownish, opalescent teeth that wear quickly. It can occur alone or together with osteogenesis imperfecta.

Denys-Drash syndrome

Rare disease caused by mutations in the WT1 gene, with early-onset kidney damage, disorders of sex development and a high risk of Wilms tumour.

Deoxycholic acid

Bile acid that destroys fat cells when injected and is approved for treating a double chin. Swelling, pain and numbness at the injection site are common; rarely, nerve irritation causes a crooked smile.

Deoxypyridinoline

Collagen cross-link component released during bone breakdown that can be measured in urine. Raised levels indicate increased bone turnover, for example in osteoporosis or bone metastases.

Depemokimab

Long-acting antibody against interleukin-5 that needs to be injected only twice a year and was developed for severe eosinophilic asthma.

Dependent personality disorder

Personality disorder with a pervasive need to be taken care of, fear of being alone and difficulty making one’s own decisions. Psychotherapy can strengthen independence.

Depersonalisation

Experience of perceiving oneself as strange, unreal or as if from outside. Brief episodes occur with stress or lack of sleep; persistent states are regarded as a disorder in their own right.

Depolarisation

Reduction of the electrical voltage across the cell membrane, usually due to inflowing sodium ions. If it exceeds a threshold, an action potential arises in nerve and muscle cells.

Depot preparation

Dosage form that releases a drug slowly over weeks to months after injection or implantation. It is used, for example, for antipsychotics, hormone therapies or contraceptives to replace daily doses and improve adherence.

Deprescribing

Planned, medically supervised stopping or reducing of medicines whose benefits no longer outweigh their harms. It is especially important in older people taking many medicines.

Depression

Mental illness with persistent low mood and loss of interest and drive lasting at least two weeks. It is treatable, for example with psychotherapy and medication.

Derealisation

Experience that the surroundings seem unreal, strange or as if behind glass, although the person knows this is not true. It occurs briefly with stress or exhaustion and more often in anxiety and dissociative disorders.

Dermabrasion

Aesthetic procedure in which the upper skin layers are mechanically sanded away, for example to smooth scars or uneven areas. The skin then needs days to weeks to heal; risks include infection, pigment changes and scarring.

Dermaplaning

Cosmetic removal of superficial dead skin cells and fine facial hair with a blade. The skin may be more sensitive afterwards; it is not advised in active acne or inflammation.

Dermatitis

Inflammatory skin reaction with redness, itching, scaling or blisters, for example as contact dermatitis caused by irritants or allergens.

Dermatitis herpetiformis

Intensely itchy, grouped blisters on the elbows, knees and buttocks. It is the skin form of coeliac disease and improves on a gluten-free diet.

Dermatochalasis

Age-related excess skin of the upper eyelid, colloquially “hooded eyelids”. Pronounced forms can restrict the visual field; eyelid surgery carries risks such as scarring and dry eyes.

Dermatofibroma

Benign, firm, brownish skin nodule, often on the legs, that dimples inwards when squeezed from the sides. It is harmless and only needs removing if it causes problems or is unclear.

Dermatofibrosarcoma protuberans

Rare, slow-growing malignant tumour of the dermis, usually on the trunk. It grows into the surrounding tissue with extensions but rarely spreads; complete removal with margin control is crucial, and imatinib can help in advanced cases.

Dermatologically tested

Claim on cosmetics that skin tolerance was tested under medical supervision. The scope and number of participants of such tests are not prescribed.

Dermatology

Medical specialty for diseases of the skin, hair, nails and mucous membranes as well as sexually transmitted infections and allergies.

Dermatome

Area of skin supplied by the fibres of a single spinal nerve root. Deficits in particular dermatomes help locate a slipped disc.

Dermatomyositis

Autoimmune disease that inflames muscles and skin; typical features are muscle weakness at the shoulders and hips and reddish-violet skin changes on the eyelids and knuckles. In adults, an associated cancer should be looked for.

Dermatosis papulosa nigra

Many small, dark, harmless papules on the face that occur mainly in people with dark skin. They resemble small seborrhoeic keratoses.

Dermis

Middle layer of the skin with collagen fibres, blood vessels, nerves, hair roots and glands; it gives the skin its firmness.

Dermographism

Skin reaction to pressure or scratching: in red dermographism redness appears, in the urticarial form an itchy wheal along the scratch line. White dermographism is typical of atopic eczema.

Dermoscopy

Examination of skin lesions with an illuminated magnifying device; it improves the early detection of skin cancer.

Dersimelagon

Oral melanocortin-1 receptor agonist that stimulates melanin production. It is being tested in studies in erythropoietic protoporphyria.

Descemet’s membrane

Strong basement membrane between the corneal stroma and the corneal endothelium. It is part of modern corneal transplants in which only this layer with endothelium is transplanted.

Descemetocele

Bulging of the innermost corneal layer when a deep corneal ulcer has destroyed all the layers above it. It indicates an imminent risk of perforation and is an emergency.

Descending colon

Descending section of the large intestine on the left side of the abdomen that continues into the sigmoid colon. It is firmly attached to the rear abdominal wall.

Descending perineum syndrome

Descent of the perineum below the normal level during straining, usually due to pelvic floor weakness. It can cause defecation disorders, incontinence and nerve stretching.

Desflurane

Inhalational anaesthetic with very rapid induction and emergence. Because of its strong greenhouse effect, its use is increasingly being restricted.

Desipramine

Tricyclic antidepressant with predominantly noradrenergic action and a metabolite of imipramine. It causes less drowsiness than other tricyclics.

Desloratadine

Second-generation antihistamine and active metabolite of loratadine. It relieves symptoms of hay fever and hives and usually causes hardly any drowsiness.

Desmoid tumour

Benign but locally aggressive connective tissue tumour that grows into neighbouring tissue but does not spread. Because it often stops growing spontaneously, it is frequently just monitored at first; a link to familial adenomatous polyposis is known.

Desmoplastic melanoma

Rare form of melanoma with fibrous tissue, often without pigment, that can look like a scar. It grows deeply and tends to spread along nerves.

Desmopressin

Synthetic variant of the hormone vasopressin that increases water reabsorption in the kidney. It is used in diabetes insipidus, bedwetting and certain bleeding disorders, among other conditions.

Desmosome

Spot-like adhesive junction between cells that provides mechanical strength, particularly in the skin and heart muscle. Autoantibodies against desmosomal proteins cause pemphigus vulgaris.

Desogestrel

Progestogen used in combined pills and as an oestrogen-free progestogen-only pill. The oestrogen-free form is also suitable when oestrogens are not tolerated or not permitted; irregular bleeding is common.

Detrusor muscle

Muscle layer of the bladder wall that contracts during urination. Overactivity causes urgency, weakness causes residual urine.

Deucravacitinib

Oral selective inhibitor of tyrosine kinase 2 (TYK2) for the treatment of moderate to severe psoriasis. It blocks signalling pathways of interleukin-23 and type I interferons.

Deuruxolitinib

Oral JAK1/2 inhibitor for the treatment of severe alopecia areata in adults, approved in the USA. As with other JAK inhibitors, infections, blood count changes and thrombosis must be watched for.

Deutetrabenazine

VMAT2 inhibitor that reduces dopamine release and is used against chorea in Huntington’s disease and tardive dyskinesia. It is approved in some countries; depression is an important side effect.

Dexamethasone

Very potent, long-acting corticosteroid used, for example, in cerebral oedema, severe inflammation, to prevent nausea during chemotherapy and in severe COVID-19. Prolonged use carries the typical corticosteroid side effects.

Dexamethasone suppression test

Function test in which dexamethasone is taken in the evening and cortisol is measured the next morning. If normal suppression is absent, Cushing’s syndrome is suspected.

See also: Cushing’s syndrome, Cortisol

Dexibuprofen

The active mirror-image form (S-enantiomer) of ibuprofen, which relieves pain and inflammation. A lower dose than conventional ibuprofen is therefore sufficient.

Dexketoprofen

NSAID pain reliever, the active dextrorotatory form of ketoprofen, used short term for acute mild to moderate pain. It acts quickly and, like other NSAIDs, can strain the stomach and kidneys.

Dexlansoprazole

Proton pump inhibitor with delayed, dual-phase release that prolongs acid suppression over the day. It is approved for reflux disease in the USA, among other countries.

Dexmedetomidine

Alpha-2 agonist for sedation in intensive care in which patients usually remain rousable and responsive. It hardly depresses breathing but can lower pulse and blood pressure.

Dexpanthenol

Precursor of vitamin B5 used in ointments, creams and nasal sprays to care for dry or irritated skin and mucous membranes.

Dexrazoxane

Protective agent that binds iron and can thus reduce heart damage caused by anthracyclines such as doxorubicin. It is also used to treat accidental extravasation of these cytostatic drugs.

DHEA

Dehydroepiandrosterone, a precursor hormone of the sex hormones from the adrenal cortex. Its levels fall with age; a benefit of supplements against ageing is not proven.

Diabetes insipidus

Rare disorder of water balance with large volumes of urine and intense thirst; not related to diabetes mellitus.

Diabetes mellitus

Persistently raised blood sugar. In type 1 the hormone insulin is lacking, in type 2 it does not work adequately. Untreated, diabetes damages blood vessels, nerves, kidneys and eyes.

In depth: Diabetes Mellitus →

Diabetic foot

Damage to the feet in diabetes caused by nerve and circulation problems; small wounds can heal poorly.

Diabetic maculopathy

Damage to the centre of the retina in diabetes, usually due to fluid accumulation. It is a common cause of vision loss and is treated with injections into the eye or laser.

Diabetic nephropathy

Kidney damage caused by long-standing diabetes that shows early on as protein in the urine. Good control of blood sugar and blood pressure slows its progression.

Diabetic polyneuropathy

Nerve damage resulting from many years of raised blood sugar that usually begins with tingling and numbness in the feet. It increases the risk of unnoticed foot injuries.

Diabetic retinopathy

Damage to the retinal blood vessels caused by many years of raised blood sugar; regular eye checks help prevent loss of vision.

Diabetology

Medical specialty concerned with the treatment of diabetes mellitus and its complications. Diabetologists work closely with diabetes educators, dietitians and podiatrists.

Diadochokinesia

Ability to alternate opposing movements, such as turning the hand, rapidly and evenly. It is tested in the neurological examination, mainly to assess cerebellar function.

Diagnosis

Identification of a disease on the basis of the medical history, examination and findings.

Dialectical behaviour therapy

Behavioural therapy approach originally developed for borderline personality disorder that combines acceptance and change. Its core is skills training in mindfulness, emotion regulation, distress tolerance and interpersonal effectiveness.

Dialysis

Blood purification procedure that removes toxins and excess water from the blood in kidney failure, usually several times a week using a machine.

Dialysis access steal syndrome

Condition in which the dialysis fistula draws off so much blood that the hand is undersupplied. Cold, pale or painful fingers, up to wounds, require prompt vascular surgical correction.

Dialysis disequilibrium syndrome

Neurological complication of the first dialysis sessions in which too rapidly lowered urea levels trigger brain swelling. Headache, nausea, confusion and even seizures can usually be avoided with short, gentle initial dialyses.

Diamond-Blackfan anaemia

Rare congenital anaemia in which the bone marrow specifically produces too few red blood cells. It usually appears in the first year of life.

Diamorphine

Chemically heroin; in Germany it is approved as a medicine for substitution treatment of severely opioid-dependent people under strict conditions in specialised facilities. It is injected under supervision.

Diapedesis

Migration of white blood cells through the wall of small blood vessels into the surrounding tissue. It is a central step in the inflammatory response.

Diaphoresis

Technical term for heavy sweating, for example with fever, low blood sugar or a heart attack. Cold sweat together with chest pain is a warning sign.

Diaphragma sellae

Circular plate of dura mater above the sella turcica with an opening for the pituitary stalk. Pituitary tumours often grow upwards through it.

Diarrhoea

More than three unformed or liquid stools a day, usually due to viral infections and less often to bacteria, medicines or bowel diseases. Drinking enough is important; blood in the stool, high fever or duration of more than a few days should be investigated.

Diascopy

Examination in which a glass slide is pressed onto a skin lesion. If the redness disappears, it is due to dilated blood vessels; if it remains, this suggests bleeding into the skin or a granuloma.

Diastema

Gap between two teeth, usually between the upper central incisors. It is often harmless and can be closed orthodontically or with fillings if desired.

Diastematomyelia

Rare congenital malformation in which the spinal cord is split lengthwise into two halves by a bony or fibrous septum. It can lead to gait problems, foot deformities and bladder disorders.

Diastole

Relaxation and filling phase of the heart between two beats, during which the ventricles refill with blood. The lowest arterial pressure in this phase is the lower blood pressure value.

Diastolic murmur

Heart murmur in the filling phase between the second and first heart sounds. Unlike many systolic murmurs, it is practically always pathological, for example in aortic regurgitation or mitral stenosis.

Diastrophic dysplasia

Rare inherited skeletal dysplasia with short stature, joint contractures, clubfeet, a protruding “hitchhiker” thumb and swelling of the ear in infancy. It is caused by mutations in the SLC26A2 gene.

Diazepam

Long-acting benzodiazepine for anxiety, muscle tension and seizures. Taken regularly for several weeks, it can lead to dependence.

Diclofenac

Pain reliever and anti-inflammatory from the NSAID group, available as tablets or gel.

Dicrotic pulse

Pulse form with a distinct second wave after closure of the aortic valve, i.e. in diastole. It can occur with low vascular resistance, for example in sepsis, or weak pump function.

Dienogest

Progestogen used in contraceptive pills and as a single agent to treat endometriosis.

Dientamoeba fragilis

Intestinal protozoan that is frequently detected in stool. Whether it causes symptoms such as abdominal pain and diarrhoea or simply lives harmlessly in the gut is scientifically disputed.

DIEP flap

Free flap of lower abdominal skin and fat supplied by the deep inferior epigastric perforator vessels and connected microsurgically. It is used mainly for breast reconstruction with the patient’s own tissue and spares the abdominal muscles.

Dietitian

Health professional who plans nutritional therapy and advises patients, for example with diabetes, kidney disease or malnutrition. Services can be prescribed by a doctor.

Dieulafoy lesion

Unusually large artery directly beneath the mucosa, usually in the stomach, that can suddenly bleed heavily through a small defect. It is a rare cause of severe gastrointestinal bleeding and is treated endoscopically.

Difelikefalin

Peripherally acting kappa opioid agonist injected after dialysis for moderate to severe itching in dialysis patients. It hardly enters the brain.

Differential diagnosis

Distinguishing between diseases with similar symptoms in order to find the correct diagnosis.

Diffuse large B-cell lymphoma

Most common aggressive non-Hodgkin lymphoma in adults, causing rapidly growing lymph node swellings. Standard treatment combines chemotherapy with rituximab.

Diffusing capacity

Lung function value that indicates how well gases pass from the alveoli into the blood. It is reduced, for example, in pulmonary fibrosis or emphysema.

Diffusion

Passive movement of particles from a region of higher to lower concentration without the use of energy. This is how oxygen and carbon dioxide pass through the thin wall of the alveoli, for example.

DiGeorge syndrome

Genetic disease caused by a missing piece of chromosome 22, with heart defects, immunodeficiency due to an absent thymus and low calcium.

Digital disimpaction

Careful removal of hardened stool from the rectum with a gloved finger. It is performed only on medical instruction, with lubricant and under observation, because circulatory reactions and mucosal injuries are possible.

Digital eye strain

Tired, dry eyes and headaches after long periods of screen work; regular breaks help.

Digital health application (DiGA, Germany)

Health app reviewed by the German Federal Institute for Drugs and Medical Devices (BfArM) that can be prescribed by a doctor and paid for by statutory health insurance.

Digital rectal examination

Palpation of the rectum and surrounding area with a gloved finger, for example to assess the prostate, haemorrhoids, tumours or bleeding. It is brief and usually hardly painful.

Digital subtraction angiography

Imaging of blood vessels with contrast medium in which an image without contrast is subtracted from the image with contrast so that only the vessels remain visible. It is used for diagnosis and simultaneous treatment of vascular narrowing.

Digitalis

Cardiac glycosides from foxglove used in heart failure and atrial fibrillation; narrow therapeutic range.

Digitalis toxicity

Poisoning by cardiac glycosides such as digoxin or digitoxin with nausea, visual disturbances such as yellow vision and dangerous arrhythmias. It is favoured by potassium deficiency and kidney failure; digoxin-specific antibody fragments serve as the antidote.

Digoxin-specific antibody fragments

Antibody fragments that bind digoxin and digitoxin and are given as an antidote in severe digitalis poisoning with arrhythmias or high potassium.

Dihydralazine

Directly vasodilating blood pressure drug used, among others, in severe high blood pressure in pregnancy. Palpitations and headache are common; rarely a lupus-like syndrome occurs.

Dihydrocodeine

Opioid for relieving dry cough and moderately severe pain. Typical side effects are constipation and drowsiness; dependence can develop with long-term use.

Dihydroergotamine

Ergot alkaloid that can be used in severe migraine attacks or cluster headache. Because of its vasoconstrictive effect, it is contraindicated in cardiovascular disease and pregnancy.

Dihydrotestosterone

Particularly potent male hormone formed from testosterone by the enzyme 5-alpha reductase. It controls prostate growth, body hair and hereditary hair loss.

Dilated cardiomyopathy

Heart muscle disease in which the left ventricle is enlarged and pumps weakly. Causes include genetic factors, previous myocarditis, alcohol or certain chemotherapies; the result is heart failure.

Diltiazem

Calcium channel blocker that lowers heart rate and blood pressure and widens the coronary arteries. It is used in angina and for rate control in atrial fibrillation; as an ointment it helps with anal fissures.

Dimenhydrinate

Antihistamine used against nausea and vomiting, especially in motion sickness. It often causes drowsiness.

Dimercaprol

Chelating agent that binds heavy metals such as arsenic, mercury and gold and is injected as an antidote. In many cases it has been replaced by better-tolerated agents such as DMPS.

Dimethyl fumarate

Capsule for basic therapy of relapsing multiple sclerosis with anti-inflammatory and cell-protective effects. Flushing and gastrointestinal complaints are common at the start; regular lymphocyte checks are needed.

Dimethylaminophenol (4-DMAP)

Antidote for cyanide poisoning that deliberately generates methaemoglobin, to which cyanide binds. In smoke inhalation poisoning it is problematic because it further reduces oxygen delivery.

Dimeticone

Silicone oil used as an antifoaming agent for flatulence that makes gas bubbles in the gut collapse. As a head lice treatment, it physically coats lice and nits without a nerve poison.

Dimetindene

First-generation antihistamine used as a gel against itching and as drops for allergic reactions. Taken by mouth, it can cause drowsiness.

Dinoprostone

Prostaglandin E2 used as a vaginal gel or insert to ripen the cervix and induce labour. Because contractions can become too strong, the baby is monitored by CTG.

Diogenes syndrome

Description of marked self-neglect with squalor in the home, often associated with hoarding and social withdrawal, usually in older people. Dementia, depression or other mental illnesses are often behind it.

Diphenhydramine

First-generation antihistamine used as an over-the-counter sleep aid and against travel sickness. It causes drowsiness, has anticholinergic effects and can still impair reaction time the next morning.

Diphtheria

Bacterial infection of the throat with membranes and a poisonous toxin; rare thanks to vaccination.

Diphyllobothriasis

Infection with the fish tapeworm after eating raw or undercooked freshwater fish. It is often mild but can cause anaemia by depleting vitamin B12.

Diplacusis

Hearing disorder in which the same tone is perceived at different pitches in the two ears or as double. It can occur with inner ear damage, sudden hearing loss or Ménière’s disease.

Diploe

Spongy bone layer between the outer and inner tables of the skull bones. It contains red bone marrow and veins that can spread infections.

Diplopia

Perception of double images, usually due to impaired coordination of the eye muscles. New, sudden double vision should be investigated promptly.

DIPSS

Dynamic International Prognostic Scoring System for primary myelofibrosis that assesses age, white cell count, haemoglobin, blasts and constitutional symptoms at any point in the disease.

Dipyridamole

Platelet inhibitor and vasodilator used in combination with aspirin to prevent recurrent stroke. Headaches are common at the start.

Direct bilirubin

Fraction of bilirubin that has been conjugated with glucuronic acid in the liver and is excreted with bile. A rise indicates impaired bile excretion, for example due to bile duct obstruction or liver cell damage.

Direct oral anticoagulants (DOACs)

Oral anticoagulants such as apixaban or rivaroxaban that do not require regular clotting tests.

Direct pulp capping

Dental procedure in which a healthy pulp that has been exposed accidentally or by caries is covered with a healing-promoting material. The aim is to keep the tooth vital and avoid root canal treatment.

Dirofilariasis

Infection with roundworms of the genus Dirofilaria that normally infect dogs and are transmitted by mosquitoes. In humans they usually cause single nodules under the skin, around the eye or in the lung.

Diroximel fumarate

Drug for relapsing multiple sclerosis that is converted in the body to monomethyl fumarate, like dimethyl fumarate. It was developed to reduce gastrointestinal complaints; flushing and a drop in lymphocytes remain possible.

Disc displacement (jaw joint)

Displacement of the cartilage disc in the jaw joint, often forwards. It often shows as clicking on opening and can restrict mouth opening.

Disease management programme (Germany)

Structured treatment programme of the German statutory health insurers for people with chronic conditions such as diabetes, coronary heart disease, asthma or COPD. Regular check-ups and education are intended to improve the course.

Disinfection

Process that kills or inactivates pathogens on skin, hands, surfaces or instruments to the point that they can no longer cause infection. Unlike sterilisation, it does not reliably eliminate all microorganisms and spores.

Disopyramide

Class Ia antiarrhythmic with pronounced anticholinergic effects. It is occasionally used in hypertrophic obstructive cardiomyopathy to reduce the pressure gradient.

Dissociation

Feeling of being detached from oneself or one’s surroundings, for example after distressing experiences.

Dissociative amnesia

Memory gap for important personal, usually distressing experiences that cannot be explained by a brain disease. It can be associated with aimless wandering (fugue).

Dissociative disorder

Mental disorder in which the normally integrated experience of memory, identity, perception or body control partly falls apart. It is often linked to severe stress; treatment is psychotherapeutic.

Dissociative fugue

Sudden, unexpected travel away from home with loss of memory of one’s own identity or past. It is often associated with severe stress.

Dissociative identity disorder

Severe dissociative disorder in which two or more distinct personality states alternately determine experience and behaviour. It is usually associated with severe trauma in childhood.

Distal convoluted tubule

Section of the renal tubule after the loop of Henle in which sodium, chloride and calcium, among others, are reabsorbed in a finely regulated way. Thiazide diuretics act here.

Distal occlusion (Class II malocclusion)

Bite misalignment in which the lower jaw is positioned too far back relative to the upper jaw, so that the upper front teeth often protrude markedly. Depending on severity and age, it is treated orthodontically or surgically.

Distal oesophageal spasm

Oesophageal motility disorder with premature, uncoordinated contractions in the lower section. It causes swallowing difficulties and chest-pain-like cramps; diagnosis is by manometry.

Distal radioulnar joint

Joint between the ulna and radius at the wrist that allows rotation of the forearm. It is stabilised by a fibrocartilage complex (TFCC), injury to which causes ulnar-sided wrist pain.

Distichiasis

Congenital or acquired extra row of eyelashes growing from the openings of the meibomian glands. The lashes can rub on the cornea and cause irritation.

Distigmine

Long-acting cholinesterase inhibitor that can be used for weak bladder muscles and myasthenia. Too high doses lead to salivation, diarrhoea and a slow pulse.

Disulfiram

Drug that inhibits alcohol breakdown so that drinking alcohol causes nausea, flushing and palpitations. It was used to prevent relapse in alcohol dependence and is no longer marketed in Germany.

Dithranol

Older, effective agent against psoriasis plaques that can stain skin and clothing brown. It is usually applied as short-contact therapy.

Diuretic

Drug that increases the excretion of salt and water through the kidneys, for example in high blood pressure or heart failure.

Divarasib

Inhibitor of the KRAS G12C mutation being studied in lung and bowel cancer that is more potent in the laboratory than earlier substances of this class.

Diversion colitis

Inflammation of a section of the large intestine that has been excluded from the faecal stream, for example after creation of a stoma. It is caused by a lack of short-chain fatty acids; reversal usually cures it.

Diverticula

Small pouches of the bowel wall, mostly in the large intestine and more common with age. When they become inflamed, this is called diverticulitis.

Dix-Hallpike manoeuvre

Positional test in which the head is turned and quickly brought backwards below the level of the couch. Rotational vertigo with typical nystagmus confirms benign paroxysmal positional vertigo.

DLQI

Dermatology Life Quality Index, a ten-question questionnaire on the impairment of quality of life caused by skin diseases. Scores above 10 are considered a significant burden.

DMEK

Descemet membrane endothelial keratoplasty, a corneal transplant in which only Descemet’s membrane with endothelium is transplanted. It is standard in Fuchs endothelial dystrophy and often allows rapid improvement in vision.

DMFT index

Measure of caries burden that adds up the number of decayed, missing and filled permanent teeth. It is used in population studies of oral health.

DMPS

Dimercaptopropane sulfonic acid, a chelating agent for treating poisoning with mercury, arsenic and lead. It can be given as a capsule or injection.

DNA

Deoxyribonucleic acid: carrier of the genetic information in every cell, built as a double helix from four building blocks (A, T, G, C).

DNA methylation

Epigenetic change in which methyl groups are attached mainly to cytosine building blocks of DNA, which can switch genes off without changing the genetic information itself. It is important for development, imprinting and X inactivation and is often disturbed in cancer.

DNA replication

Duplication of the genetic information before each cell division, in which the two DNA strands are separated and each is completed by polymerases. Errors are corrected by repair systems; if these fail, mutations can arise.

DOAC score

Score from 2023 for estimating bleeding risk in atrial fibrillation on direct oral anticoagulants that weights age, kidney function, previous bleeding and concomitant medication, among other factors.

Dobutamine

Drug given as a continuous infusion that increases the force of heart contraction. It is used in intensive care for acute heart failure or cardiogenic shock.

Docetaxel

Taxane cytostatic drug that prevents the breakdown of microtubules and so stops cell division. It is used in breast, prostate, lung and stomach cancer, among others; blood count changes, fluid retention, nail damage and nerve damage are typical.

Dofetilide

Class III antiarrhythmic that blocks potassium channels and is intended to maintain sinus rhythm in atrial fibrillation. Because of the risk of dangerous QT prolongation, treatment is started in hospital.

Döhle bodies

Pale blue inclusions in the cytoplasm of neutrophils that appear on blood smears in severe infections or inflammation. They derive from remnants of the rough endoplasmic reticulum.

Doloplus scale

Observation tool for assessing pain in people who can no longer express themselves, for example in advanced dementia. It rates somatic, psychomotor and psychosocial reactions.

Dolutegravir

Integrase inhibitor that prevents the HIV genome from being integrated into human cells. It is part of many recommended HIV combination therapies and has a high barrier to resistance.

Dominant-negative effect

Mechanism in which an altered protein is not only non-functional but also disrupts the normal protein from the healthy gene copy. This is typical of proteins made of several subunits, such as collagen in osteogenesis imperfecta.

Domperidone

Dopamine antagonist that speeds up gastric emptying and relieves nausea without entering the brain to any significant extent. Because of a risk of arrhythmias, it is approved only at low doses and for short periods.

Donanemab

Antibody that clears amyloid plaques already deposited in the brain and can somewhat slow decline in early Alzheimer’s disease. As with lecanemab, ARIA side effects are possible, especially in carriers of two APOE4 alleles.

Donath-Landsteiner antibody

Cold-reacting autoantibody that binds to red blood cells in the cold and triggers their destruction on rewarming. It causes paroxysmal cold haemoglobinuria.

Donepezil

Acetylcholinesterase inhibitor that can temporarily stabilise mental performance in mild to moderate Alzheimer’s dementia. Common side effects are nausea and a slow pulse.

Donidalorsen

Antisense oligonucleotide that reduces the production of prekallikrein in the liver and is intended to prevent attacks of hereditary angioedema. It is given subcutaneously at intervals of several weeks.

Donohue syndrome

Extremely rare, most severe form of congenital insulin resistance caused by mutations in the insulin receptor gene. Infants show severe growth failure, absent subcutaneous fat and fluctuating blood sugar.

Door-to-needle time

Time from a stroke patient’s arrival at hospital to the start of thrombolysis. The target is less than 60, ideally 30 minutes, because every minute costs brain tissue.

Doose syndrome

Childhood epilepsy with myoclonic-atonic seizures in which children suddenly collapse after brief jerks. The course ranges from complete remission to permanent developmental disorders.

Dopamine

Messenger in the brain that is important for movement, motivation and the sense of reward. A deficiency plays a central role in Parkinson’s disease.

Dopamine agonists

Drugs that directly stimulate dopamine receptors and are used in Parkinson’s disease, restless legs syndrome and prolactinomas. Rarely, they promote impulse control disorders such as gambling addiction.

Doping

Use of prohibited substances or methods to enhance performance in sport, such as anabolic steroids, erythropoietin or blood doping. Besides breaking the rules, there are considerable health risks such as cardiovascular damage, thrombosis and liver damage.

Doppler ultrasound

Ultrasound technique that visualises blood flow in vessels, for example when thrombosis is suspected.

Doravirine

Non-nucleoside reverse transcriptase inhibitor for the treatment of HIV infection with fewer interactions and neuropsychiatric side effects than older substances of this class.

Dorzolamide

Carbonic anhydrase inhibitor eye drops that reduce aqueous humour production and so lower intraocular pressure in glaucoma. Stinging on instillation and a bitter taste are common.

Dosage form

Form in which a medicine is used, for example tablet, capsule, syrup, suppository, spray or injection.

Dose

Amount of a medicine taken at one time or within a period.

Dose escalation

Stepwise increase in the dose of a drug, especially in early trial phases, to determine tolerability and a suitable dose. A well-known scheme is the 3+3 design.

Dose-response curve

Graph showing how the strength of a drug effect increases with rising dose; usually an S-shaped curve results. Efficacy, potency and therapeutic range can be read from it.

Dostarlimab

Monoclonal antibody against PD-1, an immune checkpoint inhibitor used, among others, in advanced endometrial cancer. Immune-mediated side effects can affect virtually any organ.

Double-barrel shotgun sign

Ultrasound image of two parallel tubes in the liver when a dilated bile duct lies next to the portal vein. It indicates bile duct obstruction.

Double bubble sign

X-ray or ultrasound finding of two air- or fluid-filled bubbles in the stomach and duodenum with no air further down the bowel. In newborns it indicates duodenal atresia.

Double chin

Accumulation of fat and slack skin under the chin caused by predisposition, weight or ageing. Treatments such as liposuction or fat-dissolving injections are possible but carry risks such as swelling, nerve irritation or irregular contours.

Double-lumen tube

Breathing tube with two separate channels that allows separate ventilation of each lung. It is used mainly in thoracic surgery.

Doula

Companion without medical training who provides emotional and practical support to women giving birth, for example through encouragement, massage or breathing help. A doula does not replace a midwife or doctor.

Downes score

Score for assessing respiratory distress in newborns based on respiratory rate, cyanosis, retractions, grunting and breath sounds. High scores indicate impending respiratory failure.

Doxazosin

Long-acting alpha-1 blocker that widens blood vessels and relaxes the muscles of the prostate and bladder neck. It is used in high blood pressure and benign prostatic enlargement; dizziness on standing at the start of treatment is typical.

Doxepin

Strongly sedating tricyclic antidepressant used in depression with agitation and sleep disturbance and, at low doses, for insomnia. In older people, drowsiness, risk of falls and anticholinergic side effects must be considered.

Doxorubicin

Anthracycline cytostatic drug that inserts itself into DNA and inhibits the enzyme topoisomerase II. It works in breast cancer, lymphomas and sarcomas; the total dose is limited because of possible heart muscle damage.

Doxycycline

Broad-spectrum antibiotic from the tetracycline group, used for example in Lyme disease or rosacea; it makes the skin more sensitive to light.

Doxylamine

Sedating antihistamine available over the counter as a sleep aid that should only be taken short term. Because of anticholinergic effects such as confusion and urinary retention, it is unsuitable for older people.

DPD deficiency

Inherited deficiency of the enzyme dihydropyrimidine dehydrogenase, which breaks down fluorouracil and capecitabine. Without dose adjustment, severe to life-threatening side effects can occur; testing before starting treatment is recommended.

DPP-4 inhibitors

Tablets for type 2 diabetes that enhance the body’s own insulin release after meals.

Dracunculiasis

Worm disease caused by the Guinea worm and transmitted via contaminated drinking water. After about a year, the female worm emerges painfully through the skin; thanks to eradication programmes, the disease has almost disappeared.

Dravet syndrome

Severe epilepsy, usually caused by variants in the SCN1A gene, that often begins in the first year of life with prolonged fever-associated seizures. Over time, various seizure types and developmental delay are added; sodium channel blockers can worsen the seizures.

Drehmann sign

Examination sign in which the leg rotates outwards involuntarily when the hip is passively flexed. It is typical of slipped capital femoral epiphysis in adolescents.

DRESS syndrome

Severe drug reaction with rash, fever, eosinophilia and involvement of internal organs such as the liver or kidney. It typically occurs two to eight weeks after starting a new medicine.

Dressler syndrome

Inflammation of the pericardium and pleura that can occur weeks after a heart attack or heart surgery. It is considered an immune reaction and is rare today.

DRG system

Payment system in which hospital cases are reimbursed as lump sums based on diagnoses, procedures and other characteristics. In Germany it has applied since 2004 as G-DRG and is gradually being supplemented by readiness-to-provide payments.

Dromotropy

Influence on conduction of excitation in the heart, especially in the AV node. Negatively dromotropic substances such as digitalis or certain calcium channel blockers slow conduction.

Dronabinol

Pharmaceutically produced tetrahydrocannabinol (THC), the main active compound of the cannabis plant. It can be prescribed for loss of appetite, nausea, spasticity or chronic pain; dizziness, drowsiness and psychiatric side effects are possible.

Dronedarone

Antiarrhythmic related to amiodarone but without iodine and with less organ toxicity. It is used to maintain sinus rhythm in atrial fibrillation but is unsuitable in severe heart failure or permanent atrial fibrillation.

Drop arm test

Shoulder examination in which the arm is passively raised sideways and the patient is then asked to lower it slowly. If the arm drops uncontrolled, this suggests a large tear of the rotator cuff.

Drospirenone

Progestogen derived from spironolactone with mild diuretic and anti-androgenic effects. It is contained in combined pills and as a progestogen-only pill; with combined preparations, the risk of thrombosis must be considered.

Droxidopa

Precursor of noradrenaline that is converted in the body and is intended to raise standing blood pressure in neurogenic orthostatic hypotension, for example in Parkinson’s disease or autonomic failure. One risk is high blood pressure when lying down, so the last dose is not taken just before bedtime.

Drug checking

Chemical analysis of drugs for active ingredient content and contaminants, combined with counselling of users. It is intended to prevent poisoning from unexpectedly strong or adulterated substances.

Drusen (retina)

Yellowish deposits beneath the retina that increase with age. Many large drusen are considered an early sign of age-related macular degeneration.

Dual-energy CT

Computed tomography that measures with two different X-ray energies. This makes it possible to distinguish materials such as uric acid, iodine or calcium, for example to detect gout deposits or analyse kidney stones.

Duane syndrome

Congenital eye movement disorder in which the abducens nerve is absent or abnormally formed. Typically, sideways movement of one eye is restricted, and the eye retracts into the socket when looking inwards.

Dubin-Johnson syndrome

Harmless inherited disorder in which the liver excretes conjugated bilirubin poorly into the bile. It causes mild, fluctuating jaundice; the liver appears dark due to pigment deposits, and treatment is usually not needed.

Duchenne limp

Gait pattern in which the upper body tilts towards the same side when standing on the affected leg to compensate for weak hip abductors. It occurs, for example, in hip osteoarthritis or after hip surgery.

Duchenne muscular dystrophy

Most common muscular dystrophy in childhood, X-linked and almost only in boys, caused by absent dystrophin. Muscle weakness begins in early childhood in the pelvis and legs; later the heart and breathing are affected.

Ductal carcinoma in situ

Early form of breast cancer in which malignant cells are confined to the milk ducts and have not yet broken through the basement membrane. It is often detected as microcalcifications on mammography and usually treated surgically, sometimes with radiotherapy.

Ductus arteriosus

Blood vessel connecting the pulmonary artery and aorta in the unborn child that normally closes after birth. If it stays open, it can strain the heart.

Ductus venosus

Blood vessel in the unborn child that carries oxygen-rich blood from the umbilical vein past the liver directly into the inferior vena cava. After birth it closes and becomes the ligamentum venosum.

Duffy blood group system

Blood group system whose protein also serves as the docking site for the malaria parasite Plasmodium vivax. People without the Duffy antigen, common in West Africa, are therefore largely protected against this form of malaria.

Duhamel procedure

Operation for Hirschsprung’s disease in which healthy colon is pulled through behind the remaining aganglionic rectum and joined to it side by side.

Duke criteria

Diagnostic criteria for infective endocarditis consisting of major and minor criteria, especially blood cultures and cardiac imaging. The combination results in classification as definite, possible or rejected endocarditis.

Duke treadmill score

Prognostic score based on exercise duration, ST depression and chest pain during a treadmill stress test. It divides people with suspected coronary heart disease into low, intermediate and high risk groups.

Dukes classification

Historical staging of bowel cancer (A to D) by depth of invasion, lymph node involvement and distant metastases. It has largely been replaced by the TNM classification but still appears in textbooks and older reports.

Dulaglutide

GLP-1 receptor agonist injected once a week. In type 2 diabetes it lowers blood sugar, promotes slight weight loss and has reduced cardiovascular events in studies; nausea and diarrhoea are common.

Dullness to percussion

Muffled, short percussion sound when fluid, consolidated tissue or an organ lies beneath the tapped area instead of air-filled lung. Typical causes are pleural effusion or pneumonia.

Duloxetine

Antidepressant that inhibits the reuptake of serotonin and noradrenaline. Besides depression and anxiety disorders, it is also approved for painful diabetic polyneuropathy.

Dumping syndrome

Symptoms after stomach surgery because food passes into the small intestine too quickly. Nausea and circulatory symptoms occur shortly after eating, and sometimes low blood sugar later.

Dupilumab

Biologic (antibody) that blocks certain inflammatory messengers; used in moderate to severe atopic eczema and asthma.

Duplex kidney

Common congenital variant with two separate renal pelvis systems in one kidney, often with a double ureter. Usually without symptoms, it can favour urinary tract infections or reflux.

Duplication (genetics)

Structural chromosomal change in which a section of DNA is present twice. Depending on size and the genes involved, it may have no consequences or cause developmental disorders, for example in Charcot-Marie-Tooth neuropathy type 1A.

Dupuytren’s contracture

Thickening of the connective tissue of the palm that causes the fingers to bend increasingly.

Dura mater

Outermost, tough membrane of the brain and spinal cord that lines the inside of the skull. Bleeding between it and the bone is called an epidural haematoma, bleeding beneath it a subdural haematoma.

Dural arteriovenous fistula

Abnormal short-circuit connection between arteries of the dura mater and a venous sinus or veins. Symptoms range from pulsatile tinnitus to brain haemorrhage; depending on risk, treatment is endovascular, surgical or by radiotherapy.

Dural tail sign

Tail-like tapering contrast enhancement of the dura mater at the edge of a tumour on MRI. It is typical of, but not proof of, a meningioma.

Durie-Salmon staging

Older staging system for multiple myeloma based on haemoglobin, calcium, amount of paraprotein and bone lesions as a measure of tumour burden. Today the R-ISS is mainly used.

Durkan test

Test for suspected carpal tunnel syndrome in which the examiner presses on the carpal tunnel for about 30 seconds. Tingling in the area supplied by the median nerve is considered positive.

Duroziez’s sign

To-and-fro murmur over the femoral artery with light pressure from the stethoscope. It is a classic sign of severe aortic regurgitation.

Durvalumab

Immune checkpoint inhibitor against PD-L1 that releases the immune system’s brake on tumour cells. It is used in lung cancer and biliary tract cancer, among others; side effects are immune-mediated inflammation of various organs.

Dutasteride

Inhibitor of both forms of 5-alpha reductase that reduces the conversion of testosterone to dihydrotestosterone and thus slowly shrinks an enlarged prostate. The effect takes months to start, and the PSA value falls by about half.

Duty to document

Legal obligation of doctors and nurses to record findings, measures and information given to patients promptly in the medical record. Patients have the right to inspect their records.

Duty to inform patients

Legal obligation of doctors to inform patients before treatment in an understandable way about its nature, risks, alternatives and prospects of success. Without adequate information, consent is generally invalid.

Dydrogesterone

Progestogen similar to natural progesterone with hardly any androgenic effect. It is used, for example, in cycle disorders, endometriosis, hormone replacement therapy and to support the second half of the cycle in fertility treatment.

Dyke-Davidoff-Masson syndrome

Rare consequence of early childhood brain damage with wasting of one cerebral hemisphere and compensatory thickening of the skull on that side. Seizures, hemiparesis and developmental disorders are typical.

Dynamic hip screw

Implant for fractures of the upper femur near the hip in which a sliding screw brings the fracture ends together under load. It is used mainly for stable fractures.

Dynapenia

Age-related loss of muscle strength that can occur independently of loss of muscle mass. It increases the risk of falls and need for care and can be markedly influenced by strength training.

Dysaesthesia

Unpleasant, often burning or electric abnormal sensation that occurs spontaneously or is triggered by normally harmless stimuli. It is a typical symptom of nerve damage, for example in polyneuropathy.

Dysarthria

Speech disorder due to impaired control of the speech muscles, in which pronunciation sounds slurred but language comprehension is preserved. When it occurs suddenly, it can be a sign of stroke.

Dyscalculia

Persistent difficulties with numbers and arithmetic despite normal intelligence.

Dyschezia

Difficult or painful defecation, for example with anal fissures, pelvic floor dysfunction or endometriosis.

Dysdiadochokinesia

Inability to perform rapidly alternating movements, such as turning the hand back and forth, smoothly. It is a typical sign of cerebellar dysfunction; if the movement is impossible, it is called adiadochokinesia.

Dysferlinopathy

Inherited muscular dystrophy due to deficiency of the protein dysferlin, which is involved in repairing the muscle cell membrane. It usually begins in young adulthood with weakness of the calf or pelvic muscles and greatly raised CK.

Dyshidrotic eczema

Itchy eczema with small, deep-seated blisters on the palms, sides of the fingers and soles of the feet.

Dyskeratosis congenita

Rare inherited disease with impaired telomere maintenance. Classic signs are net-like skin pigmentation, stunted nails and whitish mucosal changes in the mouth; bone marrow failure and an increased cancer risk are dangerous.

Dysmenorrhoea

Painful menstrual periods; severe pain can indicate endometriosis.

Dysmetria

Disturbed accuracy of movements in which the target is overshot or undershot. It is a typical sign of cerebellar damage and is seen, for example, in the finger-nose test.

Dyspareunia

Recurrent pain during sexual intercourse. Causes can include vaginal dryness, infections, endometriosis or pelvic floor tension.

Dysphagia

Difficulty or pain when swallowing, which should be investigated by a doctor.

Dysphagia diet

Specially adapted diet for people with swallowing difficulties, with puréed, soft or thickened foods and drinks. The consistency is chosen on the basis of a speech and language therapy assessment to prevent choking.

Dysphonia

Disorder of voice quality such as hoarseness, roughness or rapid voice fatigue. If it lasts longer than three to four weeks, the larynx should be examined.

Dysplasia

Abnormal development or pathological change of a tissue; in cancer medicine, a possible precursor of cancer.

Dysplastic naevus

Mole with irregular shape, colour or border that shows cellular changes under the microscope. Many such naevi increase the risk of melanoma and require regular checks.

Dyspnoea

Shortness of breath, the subjective feeling of difficult or inadequate breathing at rest or on exertion. Causes include the heart, lungs, anaemia or psychological factors; sudden severe breathlessness is an emergency.

Dysthymia

Long-lasting, milder depressive low mood over at least two years.

Dystonia

Movement disorder with involuntary muscle contractions and abnormal postures, for example torticollis (wry neck).

Dysuria

Pain or burning when passing urine, typical of cystitis.

Medical Encyclopedia: D