Kidney stones are hard, pebble-like deposits that form in one or both kidneys when certain minerals and other substances become concentrated in urine. Small stones may pass through the urinary tract with little or no discomfort, while larger stones can become stuck, block urine flow and cause severe pain or bleeding.
Symptoms
Symptoms can begin when a stone moves into the ureter, the tube that carries urine from the kidney to the bladder. They may include:
- sharp or severe pain in the back, side, lower abdomen or groin
- pain that comes and goes in waves
- pink, red or brown urine caused by blood
- nausea or vomiting
- pain or burning when urinating
- a frequent or urgent need to urinate
- cloudy or foul-smelling urine
Some small kidney stones cause no symptoms.
When urgent care is needed
Seek prompt medical care for severe pain, blood in the urine, persistent vomiting, inability to urinate or only passing a very small amount of urine. Fever or chills together with suspected kidney stone symptoms can indicate infection and obstruction and require urgent assessment. Use your local emergency medical service for severe illness, confusion, collapse or other life-threatening symptoms.
Why kidney stones form
Kidney stones can form when urine contains high concentrations of substances such as calcium, oxalate, phosphorus or uric acid. The main stone types include calcium stones, uric acid stones, struvite stones associated with infection and cystine stones related to an inherited condition.
Risk is higher in people who do not drink enough fluid, have had stones before, have a family history of stones, have recurrent urinary infections or certain digestive, metabolic or urinary tract conditions. Some medicines can also increase risk.
Diagnosis
A healthcare professional may use medical history, physical examination, urine tests, blood tests and imaging. Urinalysis can detect blood, minerals and signs of infection. Blood tests may identify abnormalities that contribute to stone formation. Imaging such as CT can show a stone’s size and location and whether it is blocking the urinary tract.
If a stone passes or is removed, laboratory analysis can identify what it is made of. People with recurrent stones may need additional testing, including a 24-hour urine collection, to guide prevention.
Treatment
Treatment depends on the stone’s size, location, type and whether it is causing blockage, infection or severe symptoms. Many small stones pass without a procedure. A healthcare professional may recommend fluids when appropriate and prescribe pain or other medicines.
Larger stones, stones that block urine flow or stones causing severe persistent symptoms may need a procedure. Treatment options include shock wave lithotripsy to break a stone into smaller pieces, ureteroscopy to remove or break up a stone, and percutaneous nephrolithotomy for selected larger stones.
Preventing another kidney stone
Prevention is most effective when it is tailored to the type of stone and the person’s test results. Drinking enough fluid, mainly water, is one of the most important measures for most people unless a healthcare professional has advised fluid restriction.
Depending on the stone type, dietary changes may involve reducing excess sodium or adjusting animal protein, calcium or oxalate intake. Do not unnecessarily eliminate calcium from the diet. Some people need medicines such as potassium citrate, a thiazide-type diuretic or other treatment based on the cause of their stones.
Related topics
- Blood in Urine (Hematuria)
- Bladder Stones
- Urinary Tract Infection
- Kidney Failure
- Kidneys and Urinary Tract
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases: Kidney Stones
- NIDDK: Symptoms and Causes of Kidney Stones
- NIDDK: Diagnosis of Kidney Stones
- NIDDK: Treatment for Kidney Stones
Last reviewed: 4 September 2026. This page provides general health information and does not replace individual medical assessment, diagnosis or treatment.