Oxalate balance studies in patients on hemodialysis for type I primary hyperoxaluria

Primary hyperoxaluria type I (PH1) always leads to end-stage renal failure (ESRF) due to deposition of calcium oxalate in the kidney. Regular dialysis therapy (RDT) can not overcome the excess production of oxalate, hence, systemic oxalate deposition occurs. The extent of tissue deposition and the rate at which oxalate accumulates influence the quality of life and survival of the patients. Therefore, an estimate of the oxalate balance needs to be made for patients on RDT. In this study, we suggest a simple model by which some of the main parameters of oxalate turnover can be assessed without using radioactive materials. Levels of oxalate, glycolate, and urea, and degrees of calcium oxalate saturation, were assessed on plasma ultrafiltrates from two patients with PH1, sampled before, at the end of a dialysis session, and over the entire interdialytic interval. In patients with PH1, oxalate increased linearly during the early phases and then the curve flattened at a concentration corresponding to approximately threefold saturation. The initial phase of the relationship was used to estimate generation rate of oxalate. The delayed phase was ascribed to the deposition of newly generated oxalate out of its miscible pool. Conversely, the relationship for glycolate and urea remained linear. This was also different from the values obtained in four patients with oxalosis-unrelated ESRF, whose oxalate levels increased linearly over the entire interdialytic interval. In the two patients with PH1, the overall oxalate generation was assessed at 4 to 7 mmol/d. The difference between generation and dialysis removal indicated that tissue deposition was greater than 50 mumol/kg body weight/d.(ABSTRACT TRUNCATED AT 250 WORDS)