Oxalate in Urine and Plasma Re-Visited: Evidence for Mild Hyperoxaluria in 24-h Urine Samples from Male and Female Patients with Calcium Urolithiasis

Abstract

In the past, a myriad of laboratory techniques has been employed for measuring oxalate, a small molecule in urine and plasma, A questionable reliability of the methods in use renders uncertain the validity of reports on oxalate in recurrent calcium urolithiasis (RCU). Apart from the analytical problems, mixing of male and female and younger and older human beings all within one group may lead to substantial errors, as was exemplified for other substances possibly involved in crystal- and stone-forming processes (1). Until recently, no superior analytical method for oxalate analysis was available. However, advances in analysis have recently been made with the advent of ion chromatography (2). Oxalate levels in urine and plasma are considered key factors for understanding the pathophysiology of RCU, the former because of its strong contribution to supersaturation with calcium oxalate, the latter because its knowledge is a pre-requisite for interpreting the renal tubular handling of oxalate. We report data on oxalate in urine and plasma obtained with the use of ion chromatography.