Uric Acid Nephrolithiasis — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

ModerateNephrologyUric Acid NephrolithiasisRACP Adult Medicine

A 65-year-old man presents with renal colic. CT KUB shows bilateral radiolucent stones. His serum urate is 0.55 mmol/L. 24-hour urine shows acidic pH (5.0), elevated uric acid excretion, and low urine volume. What type of stones are most likely?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Uric acid

Radiolucent stones (invisible on plain X-ray but visible on CT) with hyperuricosuria and persistently acidic urine pH (<5.5) are characteristic of uric acid stones. Acidic urine pH is the primary driver of uric acid crystallisation. Management includes urinary alkalinisation (target pH 6.0–7.0 with potassium citrate), increased fluid intake (>2.5 L/day), dietary purine restriction, and allopurinol for hyperuricaemia. Potassium citrate is the cornerstone of medical dissolution therapy.

Reference: eTG – 2025 – Nephrology; EAU – 2024 – Urolithiasis Guidelines