Bacteriology of upper urinary tract stones

Extensive cultures of stones and urine were performed in 215 patients who underwent an operation for upper urinary tract calculi. Microorganisms could be cultured from the stone in 1 of every 3 patients. Despite the extended culture technique urease-producing microorganisms could be cultured from the stone in only 48% of the patients with calculi that contained magnesium ammonium phosphate. This finding suggests that an infection with urease-producing microorganisms is not obligatory for the formation of this type of stone. Of the patients with calcium oxalate phosphate stones 32% had positive stone cultures, which distinguished them from patients with pure calcium oxalate stones, only 8% of whom had a positive stone culture (p less than 0.001).