Kidney stones are hard deposits that form inside the kidneys from substances in urine. They can be tiny and pass without being noticed, or large enough to block part of the urinary tract and cause severe pain.
Kidney stones are also called renal calculi. They are common in urology and can recur. NHS information estimates that up to half of people who have had kidney stones will have them again within five years.
Formation
Stones form when waste products in urine crystallise and collect in the kidney. This is more likely when urine is concentrated, when a person does not drink enough fluid, when some medicines are being used, or when a medical condition raises levels of stone-forming substances in urine.
Common types include calcium oxalate stones, calcium phosphate stones, uric acid stones, struvite stones linked to infection, and cystine stones linked to cystinuria.
Symptoms
Small stones may cause no symptoms and pass in urine. Larger stones can cause renal colic, which is often severe pain in the side or back that may move towards the lower abdomen or groin.
Other symptoms can include blood in the urine, nausea, vomiting, needing to pass urine more often, pain when passing urine, cloudy or foul-smelling urine, fever or chills if infection is present, and difficulty passing urine if there is obstruction.
Fever, uncontrolled pain, vomiting, pregnancy, a single functioning kidney, reduced urine output or signs of infection with a suspected stone need urgent medical assessment.
Diagnosis
Diagnosis is based on symptoms, examination, urine testing, blood tests and imaging. CT is commonly used in adults when the diagnosis is uncertain or complications are suspected. Ultrasound may be used in some situations, including pregnancy and follow-up.
If a stone is passed or removed, analysis can help identify its type and guide prevention.
Treatment
Many small stones pass naturally. Treatment may include pain relief, anti-sickness medicine, fluids and observation. Some people are given medicines such as an alpha blocker to help a stone pass, depending on the stone and clinical circumstances.
Stones that are large, infected, stuck, causing ongoing obstruction, or unlikely to pass may need a procedure. Options include shock wave lithotripsy, ureteroscopy with laser fragmentation, percutaneous nephrolithotomy, or, rarely, open surgery.
Prevention
Prevention depends on the type of stone and the person's risk factors. General measures include drinking enough water to keep urine pale, reducing dehydration risk, moderating salt intake and following tailored dietary advice.
People with recurrent stones may need metabolic testing, medicine, specialist urology follow-up or dietetic advice. Advice differs by stone type, so broad restrictions without knowing the stone type can be unhelpful.
Complications
Possible complications include urinary tract infection, kidney infection, hydronephrosis, kidney damage, sepsis in infected obstruction, and recurrent stones. Prompt treatment is important where a stone is blocking urine flow and infection is suspected.
See Also
References
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