A potential role of fecal oxalate-degrading activity in oxalate homeostasis in end-stage renal disease patients; a descriptive pilot study

Introduction: End-stage renal disease (ESRD) patients have significant differences in plasma oxalic acid (POx) concentration under the same treatment conditions. Objectives: In the present study, we adopted the method of redoximetric titration with a KMnO4 solution to evaluate the effect of total fecal oxalate-degrading activity (ODA) on oxalate homeostasis in ESRD patients which has never been reported before. Patients and Methods: A total of 56 participants were enrolled in this cross-sectional pilot study, including 24 healthy volunteers (a control reference group) and 32 ESRD patients. Among the ESRD patients, there were 21 hemodialysis (HD) and 11 peritoneal dialysis (PD) patients. Total ODA in fecal samples as well as POx concentration, daily urinary oxalate (UOx) and PD effluent oxalate excretion were determined. Cohen’s d was computed to calculate the effect size using post-hoc analysis. Results: Total ODA in fecal microbiota ranged from -23 to 24%/0.01 g of feces and was statistically higher in healthy volunteers compared with the ESRD patients. The ESRD patients with positive total fecal ODA status had higher UOx excretion level and lower POx concentration compared with the patients with negative total fecal ODA status. Cohen’s d effect size was 1.99 and 1.05, respectively. Total fecal ODA was an independent risk factor associated with POx elevation in the ESRD patients. Conclusion: Our pilot study firstly demonstrated a potential role of total fecal ODA in oxalate homeostasis in ESRD patients. The results might be useful for determining sample size considerations and providing groundwork for future research projects.