Impact of Regular or Extended Hemodialysis and Hemodialfiltration on Plasma Oxalate Concentrations in Patients With End-Stage Renal Disease

INTRODUCTION: Calcium oxalate supersaturation is regularly exceeded in the plasma of patients with end-stage renal disease (ESRD). Previous reports have indicated that hemodialfiltration (HDF) lowers elevated plasma oxalate (P(Ox)) concentrations more effectively compared with hemodialysis (HD). We reevaluate the therapeutic strategy for optimized P(Ox) reduction with advanced dialysis equipment and provide data on the effect of extended treatment time on dialytic oxalate kinetics. METHODS: Fourteen patients with ESRD who underwent HDF 3 times a week for 4 to 4.5 hours (regular HDF; n = 8) or 7 to 7.5 hours (extended HDF; n = 6) were changed to HD for 2 weeks and then back to HDF for another 2 weeks. P(Ox) was measured at baseline, pre-, mid-, and postdialysis, and 2 hours after completion of the treatment session. RESULTS: Baseline P(Ox) for all patients averaged 28.0 ± 7.0 μmol/l. Intradialytic P(Ox) reduction was approximately 90% and was not significantly different between groups or treatment modes [F(1) = 0.63; P = 0.44]. Mean postdialysis P(Ox) concentrations were 3.3 ± 1.8 μmol/l. A rebound of 2.1 ± 1.9 μmol/l was observed within 2 hours after dialysis. After receiving 2 weeks of the respective treatment, predialysis P(Ox) concentrations on HD did not differ significantly from those on HDF [F(1) = 0.21; P = 0.66]. Extended treatment time did not provide any added benefit [F(1) = 0.76; P = 0.40]. DISCUSSION: In contrast to earlier observations, our data did not support a benefit of HDF over HD for P(Ox) reduction. With new technologies evolving, our results emphasized the need to carefully reevaluate and update traditional therapeutic regimens for optimized uremic toxin removal, including those used for oxalate.