A retrospective analysis of the metabolic status of stone formers in the New York City metropolitan areas.

Eighty stone-forming patients were evaluated as outpatients for risk factors involved in stone formation. Analyses of the major stone risk parameters in the 24-hour collections indicated low volume (less than 2L) in about 79% of these patients. Forty percent of all patients were found to be hypocitraturic, 30% were hyperoxaluric, 18% were hypercalciuric, and 13% were hyperuricosuric. Sixty-one percent of the patients had a normal calcium load study; of these, four patients were uric acid stone formers. The remaining 39% of patients were classified as either absorptive hypercalciuric (16 patients), or fasting hypercalciuric with normal (12 patients) or elevated (3 patients) serum parathyroid hormone (PTH) levels. Of these 31 patients, 61% were not hypercalciuric on the basis of the 24-hour urine collections. The protocol provided a diagnosis in over 98% of patients. Low urinary volume was the only defect found in 5% of patients, while more than one risk factor was identified in 93%.