A biochemical basis for grouping of patients with urolithiasis.

The urinary excretion of calcium, magnesium, oxalate, creatinine, phosphate and urate was investigated in patients with urolithiasis and in normal subjects. The excretion of oxalate and urate per mole creatinine and the quotients calcium/magnesium, calcium X oxalate/magnesium and calcium X oxalate/(magnesium X creatinine) were significantly higher in stone formers than in normal subjects. The mean creatinine-correlated urinary excretion of calcium was higher and of magnesium lower in patients with urolithiasis, but the differences were statistically not significant. The urine investigation was supplemented with analysis of calcium, magnesium, creatinine, urate, bicarbonate and chloride in serum and a qualitative analysis of stone composition. A simple schedule for a biochemical grouping of patients with urolithiasis is presented and on the basis of the analytical findings it was possible to classify 67% of patients with so-called 'idiopathic stone disease' according to these principles.