What is the clinical utility of urine crystal analysis, and which crystals are typical for certain metabolic conditions?

• A. Calcium oxalate stones are common; uric acid stones occur in gout or purine disorders; cystine stones in cystinuria.
• B. Struvite stones are most common in all stone formers.
• C. Uric acid stones are never associated with metabolic disorders.
• D. Cystine stones are most common in gout.

Answer: (A)

Urine crystal analysis helps identify which crystals are precipitating in the urine, providing clues about metabolic or urinary conditions that drive stone formation and guiding prevention and management. Calcium oxalate crystals are the most common type seen in stones, reflecting widely encountered risk factors such as high oxalate or calcium levels, low urine volume, or dietary influences. Uric acid crystals arise when the urine is acidic or uric acid production is high, and they are classically linked to gout or disorders of purine metabolism. Cystine crystals indicate cystinuria, a hereditary defect in amino acid transport that leads to recurrent cystine stones. The other statements don’t fit as well: struvite stones associate more with infection by urease-producing bacteria rather than typical metabolic stone formers; uric acid stones can indeed be related to metabolic conditions; and cystine stones are not a feature of gout.