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Uric acid stones form in acidic urine — and unlike calcium stones, they can often be dissolved. How to prevent and treat them.
Evidence reviewed & updated: 2026-08 — reflects the latest published trials and guidelines.
Uric acid stones — about 5-10% of all stones — form when urine is persistently acidic (pH below ~5.5), which makes uric acid crystallize. Gout, diabetes, metabolic syndrome, and high purine intake are the classic associations. The good news: they can often be DISSOLVED by alkalinizing the urine with potassium citrate, and prevented by raising urine pH above 6.0.
Uric acid is a waste product of purine metabolism, excreted by the kidneys. At urine pH above 6.0, uric acid exists as soluble urate; below pH 5.5, it converts to insoluble uric acid and crystallizes. That's why chronic acidic urine — not necessarily high serum uric acid — is the main driver.
The acid-urine states: insulin resistance and diabetes (impaired kidney ammonia production), gout, chronic diarrhea (bicarbonate loss), and high animal-protein diets. People with metabolic syndrome are disproportionately affected.
Uric acid stones are radiolucent (they don't show on plain X-rays) — ultrasound or non-contrast CT finds them, and CT density can suggest the type. Serum uric acid is often (but not always) elevated; a 24-hour urine test confirms high urine uric acid.
The treatment advantage: uric acid stones can dissolve. Potassium citrate (or sodium bicarbonate) raises urine pH to 6.2-6.8 — the uric acid converts back to soluble urate and the stone melts over weeks to months. Allopurinol is added when urate production is high. Surgery is reserved for stones that don't dissolve or are obstructing.
Prevention targets urine pH and urate load: maintain urine pH 6.0-7.0 (alkalinization with potassium citrate is the mainstay), drink 2-2.5 L urine per day, limit purine-rich foods (organ meats, shellfish, anchovies, red meat), and limit alcohol — especially beer, which raises both urate and acid.
Avoid crash diets and rapid weight loss: fasting increases uric acid and acidifies urine, triggering stones — a known effect after bariatric surgery. If you have gout, treat it properly (allopurinol with renal dosing) — poorly controlled gout and stone disease travel together.
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