Plasma oxalate in patients with chronic renal failure receiving continuous ambulatory peritoneal dialysis or hemodialysis.

Plasma oxalate was measured in 20 patients receiving continuous ambulatory peritoneal dialysis (CAPD) and 20 patients receiving hemodialysis (HD). All patients had levels well above the reference range of less than 2.0 to 5.0 mumol/L (less than 0.18 to 0.44 mg/L), the medians being 34 mumol/L (2.99 mg/L) and 42 mumol/L (3.70 mg/L) for the two groups, respectively. Plasma oxalate did not differ significantly in the two groups. Plasma oxalate was not influenced by the number of months patients had received dialysis treatment, but a significant correlation was found between oxalate and creatinine in the 40 patients studied (P less than 0.02, r = 0.38). Predialysis oxalate levels were reduced by approximately 60% following HD, but returned to 80% of the predialysis levels within 24 hours and 95% within 48 hours. Oxalate levels did not differ significantly in samples taken before, during, and after exchanges of CAPD fluid. That the patients treated with CAPD did not have higher oxalate levels than the HD group suggests that the continuous nature of the former treatment compensates for the lower oxalate clearance by the peritoneum. The reported higher risk of oxalosis associated with intermittent peritoneal dialysis has led to a similar risk being postulated for CAPD; however, the present study indicates that if such a risk exists, it cannot be explained by higher levels of oxalate or ionized calcium in these patients.