Renal calculi occur in up to 6% of the population; men are affected more often than women.
• Stone composition. Most (75%) stones are calcium oxalate stones. Magne-sium ammonium phosphate (“struvite”) stones are associated with infection by urea-splitting bacteria (proteus), and these stones often form large staghorn calculi. Uric acid stones are seen in gout, leukemia, and in patients with acidic urine. Cystine stones are uncommon.
• Pathology. Most stones are unilateral stones that are formed in the calyx, pelvis, and urinary bladder.
• Clinical features. Calcium stones are radiopaque and can be seen on x-ray. Renal colic may occur if small stones pass into the ureters. Stones may cause hematuria, urinary obstruction, and predispose to infection.
• Treatment of stones is with lithotripsy or endoscopic removal.