The study protocol is approved by a local Ethics Committee and registered in Domestic Clinical Trial Registry (Identifier 0119U000002). Writing informed consent is obtained from all subjects participating in the study.

The study will enroll 300 participants (250 CKD patients at stage 1-5 and 50 healthy subjects). Routine biochemical parameters including blood and daily dialysate concentration of urea and creatinine, serum albumin, C-reactive protein (CRP), glucose, electrolytes, and lipid profile parameters will carry out. Total oxalate-degrading activity in fecal samples, as well as plasma oxalic acid concentration, daily urinary oxalate excretion and peritoneal dialysis effluent oxalate concentration (if any) will determine. Uric acid will also measure in serum, urine and dialysate of peritoneal dialysis patients.

The study will be followed up for 3 years. The primary endpoint is cardiovascular events, secondary endpoints are dialysis adequacy and all-cause mortality. All the endpoints will be collected, as well as other outcomes, such as chronic inflammation, dyslipidemia and dialysis dose, and so on. The outcomes will be analyzed using statistical software.