Medical Encyclopaedia › Kidney stones (short definition)
In brief: Kidney stones are solid deposits that form in the kidney from components of urine. If they enter the ureter, they can cause violent, cramp-like pain – renal colic. Urinary stones are common and often recur.
Formation and types of stone
Stones form when stone-forming substances in the urine are supersaturated and crystallise. The most common are calcium oxalate stones, followed by uric acid, calcium phosphate and infection stones; cystine stones in a hereditary metabolic disorder are rare. Contributing factors are a low fluid intake, heavy sweating, a diet rich in animal protein and salt, overweight, diabetes, gout, chronic inflammatory bowel disease and certain medicines.
Symptoms
Stones in the kidney often go unnoticed. If a stone moves into the ureter, wave-like, very severe pain occurs in the flank, which can radiate to the lower abdomen, groin or genital area, often with nausea, vomiting, an urge to urinate and blood in the urine.
Warning signs of an emergency
Fever or chills during colic can indicate an obstructed, infected kidney. This condition can lead to blood poisoning (urosepsis) and must be treated in hospital immediately; urine drainage is then usually relieved with a ureteral stent or a catheter through the skin. Pain that can hardly be controlled, no urine output or a stone in a person with only one functioning kidney also require immediate medical care.
Treatment
In the acute phase, painkillers are the priority, often non-steroidal anti-inflammatory drugs such as diclofenac, and if necessary also metamizole or opioids. Small stones up to about five to six millimetres often pass by themselves; medicines such as tamsulosin can make it easier for ureteral stones to pass (not licensed for this – so-called off-label use). Larger stones or stones that do not pass are fragmented with shock waves from outside (ESWL), removed with a laser via ureteroscopy, or, for large kidney stones, treated through a small access through the skin (percutaneous nephrolithotomy). Uric acid stones can often be dissolved with medication by alkalinising the urine.
Prevention
Anyone who has had a stone once has a significantly increased risk of further stones. The most important measure is to drink enough so that about two to two and a half litres of urine are passed every day. Little salt, moderate consumption of animal protein, a normal calcium intake from food and a healthy body weight also help. A stone analysis and, for recurrent stones, a metabolic work-up show whether targeted dietary changes or medicines make sense.
Related terms in the encyclopaedia
Renal colic, Tamsulosin, Ureter, Calcium oxalate, Uric acid, Haematuria, Shock wave lithotripsy, Ureteroscopy, Urosepsis, Gout
Sources
- Deutsche Gesellschaft für Urologie (DGU): S2k-Leitlinie „Diagnostik, Therapie und Metaphylaxe der Urolithiasis“, AWMF-Register 043-025 (Stand 2019, in Überarbeitung)
- European Association of Urology (EAU): Guidelines on Urolithiasis (jährliche Aktualisierung)
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.