Metabolic evaluation in patients with infected nephrolithiasis: Is it necessary?

Fifty-four patients with infected renal lithiasis underwent complete metabolic evaluation searching for underlying factors contributing to stone formation including urine analysis and culture. Metabolic abnormalities were significantly more present in patients with mixed infected stones (struvite+/-apatite and calcium oxalate) than in patients with pure infected stones (struvite+/-carbonate apatite): hypercalciuria in 40%, hyperoxaluria in 34% and hyperuricosuria in 28% (p < 0.05). Urinary excretion of citrate was low in both groups without statistically significant difference (238+/-117 mg/24 h vs 214+/-104 mg/24/h, t = 0.72, p = 0.5). The few metabolic abnormalities present in patients with pure infected stones should suggest that urinary tract infection could change the urine chemistry in a lithogenic direction and be only cause of stone formation.