[Studies of urinary risk factors in urolithiasis]

Urinary excretions of calcium, oxalate and uric acid were estimated in 160 stone-formers (male 118, female 42) and 257 healthy controls (male 207, female 50). Stone-formers were divided into two groups according to their stone analysis: calcium containing stone-formers and non-calcium stone-formers. Calcium stone-formers were divided again into those who had a single stone episode and multiple or recurrent stone episodes. Urinary calcium and oxalate showed significant increases in calcium stone-formers, while urinary uric acid increased only in male calcium stone-formers. Recurrent calcium stone-formers demonstrated significant high levels of urinary calcium excretion especially in males, whereas no difference of urinary oxalate excretion between recurrent and single stone-formers. The frequency distributions on the excretion of three subjects were estimated respectively in patients with calcium stone and in controls. Relative risks, risk curves and stone probabilities were proposed and compared. The higher excretion values of urinary calcium and oxalate closely related to higher risks of forming calcium stones. On the other hand, urinary uric acid did not have such a relation to calcium stone formation. We defined the states which urinary excretions exceeded 95% upper confidence limits of normal controls as hyperexcretions. Hypercalciuria was more than 200 mg/day in male and female, hyperoxaluria was 50 mg/day in male and 45 mg/day in female and hyperuricosuria was 850 mg/day in male and 650 mg/day in female according to our definition. Among male calcium stone-formers, hypercalciuria was found in 45.3%, hyperoxaluria in 26.4% and hyperuricosuria in 15.1%. While in female calcium stone-formers, hypercalciuria in 23.7%, hyperoxaluria in 26.3% and hyperuricosuria in 13.2%. Of the male calcium stone-formers 57.5% showed either or both hypercalciuria and hyperoxaluria, and recurrent stone-formers also demonstrated a higher incidence among them. Excretion products of urinary calcium and oxalate were calculated and compared in each group. Calcium stone-formers showed significant high values especially in male recurrent stone-formers. The estimation by combining some risk factors will provide more useful means of assessing severity of urinary calculous diseases and therapeutic effects of their various treatments.