CALCIUM-OXALATE STONE AGGLOMERATION REFLECTS STONE-FORMING ACTIVITY -CITRATE INHIBITION DEPENDS ON MACROMOLECULES LARGER THAN 30 KILODALTON

To evaluate the clinical utility of in vitro calcium oxalate monohydra te (COM) crystallization kinetics measurements and to determine the ef fect of quantitative removal of urinary Tamm-Horsfall glycoprotein on such measurements, we examined 24-hour, room temperature urine collect ions of patients from our Stone Clinic and of normal subjects from our research laboratories at Ochsner Medical Institutions in New Orleans, LA, and compared their COM kinetic parameters in vitro before and aft er urine ultrafiltration (30 kd). Data from 53 calcium oxalate stone-f orming patients (26% women; mean age, 47 years) who demonstrated radio graphic or other evidence of forming at least one stone were compared with data from 22 healthy volunteers (25% women; mean age, 40 years). Hypercalciuria (>7.5 mm/24 hr), hyperoxaluria (>0.5 mm/24 hr), and hyp ocitraturia (<2.0 mm/24 hr) were present in 38%, 26%, and 26% of the p atient population, respectively. Urinary creatinine, urate, calcium, c itrate, phosphate, oxalate, pH, volume, total immunoreactive-disaggreg ated Tamm-Horsfall glycoprotein, and the urine's effects on COM solubi lity, percent crystal growth inhibition, and crystal agglomeration inh ibition [tm] were determined. Calcium oxalate monohydrate agglomeratio n inhibition, [tm], was reduced in stone-forming patients. It decrease d with increasing stone frequency, making [tm] a useful tool for measu ring the risk of stone recurrence. Urinary Tamm-Horsfall glycoprotein and citrate concentrations were linearly related to COM agglomeration inhibition. Their effects were synergistic. Tamm-Horsfall glycoprotein removal from urine reduced COM agglomeration inhibition dramatically. Alkali therapy increased urinary citrate concentration and increased [tm]. Calcium oxalate monohydrate crystallization kinetics measurement s and their interactions with urinary constituents provide valuable, n oninvasive guidelines for the physician for evaluating and treating pa tients who wilt form subsequent calcium oxalate stones. (C) 1994 by th e National Kidney Foundation, Inc.