Urinary calculi composition in patients with spinal cord lesions.

Because of the reported production of predominantly phosphatic calculi by hypercalciuric patients there was a need to confirm the analysis of such stones using quantitative methods. Calcium, magnesium, ammonium, orthophosphate, oxalate, carbonate and urate were therefore determined in 148 calculi from 113 patients with spinal cord lesions. There were 145 (98%) composed of calcium phosphate and magnesium ammonium phosphate. Only trace amounts of calcium oxalate were present in most. The remaining 2% were calcium oxalate stones. The ratio of nonoxalate calcium to magnesium was inversely related to the duration of paralysis. This study revealed that, when this variable was taken into account, the composition of a stone was not related to its weight, site of occurrence, level of the cord lesion, sex of the patient, or therapy with acidifying drugs.