title: Evaluation of a simple test to estimate urine saturation with calcium oxalate in stone-forming patients.
abstract: In 43 patients with recent-onset calcium oxalate nephrolithiasis (25 male, 18 female; age range: 17-61 yr), urine saturation with calcium oxalate (CaOx) was calculated using a computer program (Equil-AT). The results in kJ/mol (normal < or = 2.0) were compared with those obtained with a simple test consisting of the addition of increasing amounts of calcium and oxalate to 3 tubes containing 10 ml urine. Development of turbidity in tube I denotes urine supersaturation with CaOx; turbidity in tubes II or III indicates lesser degrees of saturation, while a lack of turbidity (NT: no turbidity) shows undersaturation. Both saturation estimates were performed using aliquots of 24-hour urine collections. Twenty-one samples developed turbidity in tube I, 9 in tube II, and 6 in tube III, while 7 showed NT. There were no significant differences in Equil-AT values between II and III and between III and NT (p < 0.05 for I vs II and I vs III). High computer-calculated saturation values were found in 86% of group I samples and 22% of group II samples. None of the urines exhibiting turbidity in tube III or NT had high saturation values as estimated by Equil-AT. The turbidity test was also performed using freshly voided morning urine samples from the same patients. The results agreed with those obtained using the same test on aliquots of 24-hour collections, although in 10.8% of patients the morning test indicated higher levels of saturation. It is concluded that the turbidity test is a rapid, inexpensive and accurate way of estimating urine saturation with CaOx in the outpatient clinic.
authors.affiliation: Endocrinology Service, Hospital Español, Rosario, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Sánchez
authors.forename: A
authors.initials: A
authors.lastname: González
authors.forename: H D
authors.initials: HD
authors.lastname: Sarano
authors.forename: S
authors.initials: S
authors.lastname: Reinaldi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002129:Calcium Oxalate / Q000652:urine*; D003460:Crystallization; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D012984:Software; D013997:Time Factors; D014556:Urine / Q000737:chemistry
chemical_list: D002129:Calcium Oxalate