Medical management: Uric acid and cystine stones

The main metabolic abnormality for uric acid stone formation is abnormally acidic urine (urinary pH < 5.5). The most important modalities of treatment in this condition include urinary alkalization to maintain a urinary pH between 6.0 and 6.5 and high fluid intake to ensure urine output above 2 L/day. Potassium alkali is the preferred treatment over sodium alkali treatment since it is effective in raising urinary pH, lowering urinary calcium excretion, and inhibiting sodium urate-induced calcium oxalate crystallizations. Cystinuria is an inherited disorder of dibasic amino acid transport, which clinically presents nephrolithiasis or bladder stones. Physicochemically, cystine has limited solubility in the urinary environment. Therefore, its precipitation solely depends on urinary cystine supersaturation. The early diagnosis of cystinuria is significant as early prevention and treatment measures may provide protection against renal function impairment. Prevention and treatment include the provision of high fluid intake and urine alkalinity in order to exceed a urinary cystine solubility threshold of 250 mg/L (1,000 μ[micro]mol/L). Specific treatment regimens are limited and only include chelation treatment with D-penicillamine or α(alpha)-mercaptopropionylglycine. These treatment regimens are usually effective, but a number of them confer side effects.