Diagnosis and Evaluation of Nephrolithiasis

The physician evaluating a patient with nephrolithiasis needs to keep in mind the relative prevalence of various stone types. Calcium salts (oxalate, phosphate, or mixed) are the most common stone types, together accounting for 70-75% of nephrolithiasis; low urinary volume, hypercalciuria, hyperoxaluria, hypocitraturia, and hyperuricosuria are identified risk factors. Stone analysis is the most direct way to identify stone type and allows for stone-specific therapy. Beyond this evaluation of patients with acute renal colic, the cost-effectiveness of additional testing is not established for all adult first-time stone formers. A major goal of stone prevention is to reduce supersaturation. The normally higher levels of two important stone constituents, and normally lower levels of citrate, explain much, though not all, of the increased risk of stones in men. The supersaturation ratios for each stone salt that are provided by specialty laboratories are particularly helpful.