Oxalate Clearances in Calcium Oxalate Stone Forming Patients

A primary defect in membrane transport of oxalate across red blood cells has been reported in patients with idiopathic renal lithiasis (IRL); corrected by thiazide diuretics (TZ). To assess whether this is reflected in abnormal renal tubular handling of oxalate, we evaluated renal handling of oxalate in normals, patients with RL and primary hyper-oxaluria (l°ox) where the load is increased. Using an enzyme assay for oxalate (DM Wilson and RR Liedtke, Clin Chem 37: 1229 [1991]) with sensitivity of 0.5 μM/L, we established a normal value for plasma oxalate of 1.88 μM/L (N=33); range 1.11-5.15 μM/L. Since Pox is dependent on GFR, rising to 5 μM/L at GFR of 10 mL/min and rapidly below this, to 53 and 17 μM/L pre-and post-dialysis, we studied normals and stone subjects with GFR (iodothalamate clearance method) >70 mL/min. Data were developed on renal handling as follows: