Histologic change of peritoneal membrane in relation to adequacy of dialysis in continuous ambulatory peritoneal dialysis patients

Background. Long-term exposure of peritoneal membrane to bioincompatible dialysis solutions leads to structural changes and loss of ultrafiltration capability. Objective: We studied the possible relationship between histologic change and the transport characteristics of peritoneal membrane and adequacy of dialysis in continuous ambulatory peritoneal dialysis (CAPD) patients. Patients and Methods: The study included 18 CAPD patients (111 men, 7 women) who underwent a peritoneal biopsy either at initiation of treatment (group A, n = 9) or after a mean of 4 years on CAPD (group B, n = 9). The morphologic changes in the mesothelial cells and the vascular compartment and the thickness of the submesothelial collagenous zone were estimated and compared with observations from 6 patients with normal renal function who underwent biopsy of the parietal peritoneum during abdominal surgery. The relationship of the observed changes in CAPD patients to results from a peritoneal equilibration test (PET) and to adequacy of dialysis (total weekly creatinine clearance (M) and Kt/V urea] were also investigated. Results: The main histologic changes in both groups of patients were loss of mesothelial cells and decrease in the normal mesothelial surface, thickening of the submesothelial collagenous zone, and presence of vascular hyalinosis. The thickness of the submesothelial collagenous zone in both groups of patients was significantly greater than that found in controls (410 mum and 580 mum vs 50 mum, p < 0.05). Although no significant difference was found between morphologic change in the peritoneal membrane of uremic patients starting on CAPD and those who had been on peritoneal dialysis (PD) for a mean period of 4 years, a trend was observed toward more severe lesions in the latter patients. The PET, CCr, and Kt/V urea were not significantly different in the two groups of patients. Those parameters also showed no significant changes when examined at initiation of CAPD and after a mean of 4 years of PD in the same patients (group B). No significant correlations were observed between the histologic changes and the PET, CCr, or Kt/V in both groups of patients. Conclusions: Significant structural changes are observed in the peritoneal membrane of uremic patients, and those changes become worse with CAPD treatment. Structural changes are not followed by functional changes during the first 4 years on CAPD.