[Remarks on the metabolic evaluation of renal lithiasis].

Metabolic studies include certain routine investigations but which may be more or less limited or extended according to the individual case on the basis of its severity and the chemical nature of calculi. These studies are based upon the following data: analysis of one or more stones, aided and guided by methodical macroscopic examination; urine microscopy; study of urine pH which should be done by the patient himself on several samples during the 24-hour period; blood and urine calcium/phosphate balance, without omitting the measurement of urinary urea which provides information concerning protein intake and indicates its influence; oxalate balance studies and hyperoxaluria are correlated with cases of lithiasis when stones contain only calcium oxalate or a mixture of oxalate and calcium phosphate; uric acid balance, where once again the measurement of urinary urea is of fundamental importance and shows that all cases of hyperuricuria are related to a diet excessively rich in meat; urinary cystine levels with the need for a Brand reaction almost routinely in all lithiasis sufferers; electrolyte studies which may reveal a renal tubular acidosis syndrome, in fact rare; and, finally, in certain cases a magnesium balance may show a decreased erythrocyte magnesium.