Oral Vitamin D Supplementation Prevent Peritoneal Dialysis-related Peritonitis

176 eligible patients on PD at one month after being cured from an episode of peritonitis will be enrolled and randomized into two groups, including the intervention group administered Cholecalciferol (produced by Xymogen Company) 4000 U (2 capsules) per day, and the control group administered placebo 2 capsules per day. All participants will be followed for 24 months, or till the occurrence of death, permanently transfer to hemodialysis, loss of follow-up, or withdrawal from the study, whichever comes first. The primary outcome is the occurrence of subsequent peritonitis. The study aims to identify whether oral administration of vitamin D3 after curing an episode of peritonitis could reduce the risk of subsequent peritoneal dialysis-related peritonitis.