We evaluated the usefulness of periodic abdominal irrigation through the peritoneal catheter preserved after termination of peritoneal dialysis (PD) to prevent encapsulating peritoneal sclerosis (EPS). The study group included 8 patients in whom PD had been terminated (mean age: 53.1 +/- 7.1 years; mean PD duration: 119.6 +/- 37.8 months). The abdominal cavity was periodically irrigated through the peritoneal catheter preserved after PD discontinuation. The appearance rate of cancer antigen 125 (CA125-AR), corrected by body surface area, was obtained every 3 months from 4-hour dwells. Based on the creatinine levels in 4-hour dwells and plasma, the dialysate-to-plasma creatinine (D/P Cr) was also obtained. Following abdominal irrigation for more than 12 months, the peritoneal catheter was removed and a biopsy specimen was taken from the peritoneum. The CA125-AR increased 3 months after PD discontinuation, but decreased thereafter. Encapsulating peritoneal sclerosis developed in 3 of 4 patients who lacked parietal mesothelial cells (PMCs) in a peritoneal specimen. In contrast, a good prognosis was obtained in 4 patients who had PMCs. The maximum value of the change in CA125-AR (delta CA125-AR, as compared with the value at PD discontinuation) was significantly greater in the PMC+ group than in the PMC- group (8.0 +/- 2.7 vs. 3.4 +/- 3.1, p < 0.001). The D/P Cr at catheter removal was lower in the PMC+ group than in the PMC- group (0.45 +/- 0.21 vs. 0.85 +/- 0.18, p < 0.05). Our findings suggest that periodic abdominal irrigation through the peritoneal catheter preserved after PD enhances the recovery of peritoneal damage. The CA125-AR value is a useful marker of viability and proliferation of PMCs.