In the present study, we investigated longitudinal changes in peritoneal function, as calculated by the personal dialysis capacity (PDC) test, after patient withdrawal from 17 years of continuous ambulatory peritoneal dialysis (CAPD). In July 1982, a 42-year-old female was started on CAPD because of chronic renal failure. She performed CAPD without any trouble for 17 years. In July 1999, hemodialysis was introduced because of ultrafiltration failure. The CAPD catheter remained in place, and the patient subsequently performed intra-abdominal lavage, using a standard peritoneal dialysis (PD) solution, for 3 years. A PDC test was performed every 6 months before and after withdrawal from CAPD. In July 1999, the PDC test indicated a membrane area of 59,748 cm/1.73 m2, absorption of 2.72 mL/min/1.73 m2, plasma loss of 0.049 mL/min/1.73 m2, and ultrafiltration volume (UFV) of -666 mL/24 h. The dialysate-to-plasma ratio (D/P) of creatinine after 4 hours was 0.96. An abdominal computed tomography (CT) scan showed calcification of the peritoneum. In March 2000, the PDC showed an area of 44,929 cm/1.73 m2, absorption of 1.43 mL/min/1.73 m2, plasma loss of 0.092 mL/min/1.73 m2, and alpha UFV of 213 mL/24 h. In August 2000 (1 year after CAPD withdrawal), the area was 38,492 cm/1.73 m2; the absorption, 1.74 mL/min/1.73 m2; the plasma loss, 0.053 mL/min/1.73 m2; and the UFV, 348 mL/24 h. Long-term intra-abdominal lavage induced a gradual reduction in membrane area, which returned to the normal range (19,028 cm/1.73 m2) after 3 years. Ultrafiltration volume showed a gradual increase and reached its peak level (403 mL/24 h) in July 2002. After 3 years, the D/P creatinine was 0.82. However, an abdominal CT scan showed no change in the calcification of the peritoneum. From those data, we conclude that, in long-term CAPD patients, intra-abdominal lavage can induce improvement in peritoneal function, but not in calcification of the peritoneum.