[Preventive measures in stones due to infection, uric acid and cystine]

General prophylaxis of renal stone formation consists of 1. high fluid intake and 2. modest consumption of protein-rich foods. Specific prophylactic measures are based on pathophysiologic mechanisms of stone formation. In infection-induced renal stones, combined treatment with culture specific antibiotics and complete stone removal is of utmost importance. In all cases where stone fragments cannot be removed completely and/or partial obstruction remains, long-term antibiotics in combination with urine acidification by methionine (urine pH 5.6 to 6.2) are most appropriate. Prophylaxis of uric acid stones primarily consists of reducing purine intake and alkalizing the urine by potassium citrate. Only if this regimen failed or gout occurred, allopurinol should be administered. In patients with cystine stones, urine volume should be increased to greater than 3000 ml/die. Alkalizing the urine to a pH greater than 7.5 rises cystine solubility, whereas cystine excretion may be reduced by a diet low in sodium and/or low in methionine/cysteine. Thiols form mixed thiol-cysteine disulfides that are many times more soluble than cystine in urine; because of their high rate of adverse side-effects, however, these compounds are of lowest priority in the treatment of cystine stones. There is no convincing evidence for the efficacy of high dose ascorbic acid treatment in cystinuria.