Fractional Oxalate Clearance in Subjects with Normal and Impaired Renal Function

Abstract

The ¹⁴C-oxalate clearance was determined in 13 healthy subjects and 22 patients with various diseases and varying degrees of renal functional impairment, including 5 patients with primary hyperoxaluria (PH). The clearances of oxalate (C_ox) and creatinine (C_cr) were correlated (r = 0.95). The regression line intersects the ordinate at the origin, while the regression coefficient is 2.0. This implies that the fractional C_ox is constant, irrespective of the underlying disease and the degree of renal failure. Plasma oxalate (P_ox), as calculated from the urinary oxalate excretion (U_ox) and C_ox, was elevated in patients with severely impaired kidney function and those with PH. Plasma creatinine (P_cr) and P_ox were correlated as well (r = 0.83). P_ox values of patients with PH were above the 95% confidence limits of the regression line. It is of practical importance that Pox can be estimated from U_ox and C_cr when a ¹⁴C-oxalate clearance test cannot be performed. The reasons for the constancy of the C_ox/C_cr ratio are discussed, and it is suggested that the effective renal plasma flow (ERPF) is the regulating factor for the tubular secretion of oxalate.

Renal Oxalate Handling in Normal Subjects and Patients with Idiopathic Renal Lithiasis: Primary and Secondary Hyperoxaluria

“…Cattell et al, (3) showed that the FE 0 x in dogs was 1.28 using isotope dilution and perfusion techniques; secretion was blocked by PAR. Human studies showed that FE 0 x ranged from 1.05 to 1.9 in normal subjects and 1.85 to 1,67 in hyperoxaluric patients (4)(5)(6). Most of these studies are suspect because of indirect or insensitive measures of plasma oxalate (Pox), or non-physiological conditions.…”

Plasma Oxalate in Chronic Renal Failure and Normal Subjects: Methodological Problems

“…The results of serum oxalate determinations in normal subjects reported by Borland et al [1] in their recent paper (0-55 um ol/l) are far out of the range found in normal subjects as determined by in vivo isotope clearance meth ods (below 3 pm ol/l) [2], The reason why in many earlier studies in which chemical methods were used concentra tions are reported exceeding these low values by one order of magnitude is not clear [3), but in more recent studies [2,3,[6][7][8][9][10][11][12][13] normal values much closer to the true value were found, i.e. at least lower than 6 pm ol/l (table 1).…”

Urinary Oxalate Excretion during Intravenous Infusion of Diuretics in Man

“…We are unaware of studies in man examining intrarenal oxalate handling. In earlier studies in man, we found a constant ratio of about 2 between the clearances of l4C-oxalate and creatinine [7,8]. In this letter, we present the oxalate excretion in two studies before and after intravenous infusion of diuretics in healthy sub jects.…”