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.