We present two cases of peritonitis shortly after endoscopic examination of the large bowel with polypectomy in patients on continuous ambulant peritoneal dialysis (CAPD) despite the standard preventive measure to drain the dialysate from the abdomen prior to the procedure. We have reviewed the current literature on this topic. These cases demonstrate that the administration of prophylactic broad-spectrum antibiotics next to the drainage of the abdomen prior to colonoscopy in CAPD patients should be considered as recommended in the International Society for Peritoneal Dialysis (IS PD) guidelines 2005.