When should patients with symptomatic urinary stone disease be evaluated metabolically?

To determine the optimal time at which to assess the urinary risk factors for calcium stone formation, we followed 11 patients after an episode of acute renal colic with sequential 24-hour urine collections, first in the hospital and then at regular intervals after they were discharged from the hospital. The changes that occurred in the urinary risk factors were compared to those of a control group in which samples were collected during the same interval. The in-hospital 24-hour urine volumes were high but decreased gradually to approach the relatively constant volume of the control group by 3 months. The opposite trend occurred with respect to the 24-hour urinary excretion of calcium. There were no significant changes in the 24-hour urinary pH or excretions of oxalate, uric acid and alcian blue precipitable polyanions. The over-all effect was to cause a progressive increase in the probability of stones forming in the patients. The accurate assessment of the urinary risk factors of calcium stone disease requires at least a 3-month delay following acute renal colic. This delay usually will provide sufficient time for the stone to pass and for the patient to return to the normal dietary and fluid intake.