Longitudinal Study of Peritoneal Membrane Function in Continuous Ambulatory Peritoneal Dialysis: Relationship with Peritonitis and Fibrosing Factors

Abstract

BackgroundThe peritoneal equilibration test (PET) is a useful assessment of peritoneal function in continuous ambulatory peritoneal dialysis (CAPD) patients. However, the natural course of longitudinal change in peritoneal transport is not well defined.PatientsWe studied 105 unselected CAPD patients. Average age at enrollment was 50.7 ± 11.3 years.MethodsA PET was performed at enrollment. Peritoneal transport was expressed as dialysate-to-plasma creatinine ratio at 4 hours (D/P). Fibrosing factors and mesothelial cell markers, including TGFJJ, epidermal growth factor (EGF), platelet-derived growth factor (PDGF), hyaluronan, and cancer antigen 125 (CA125), were measured in overnight peritoneal dialysate effluent (PDE). Patients were followed for two years. Peritonitis episodes were recorded. Severe peritonitis was defined as an episode that required catheter removal or antibiotic therapy for more than 3 weeks. After two years, 75 patients were still alive and on CAPD.ResultsThe PET was repeated in 64 patients, of whom 35 were male and 9 had diabetes. The change in D/P over two years was represented as ΔD/P. No significant change in peritoneal transport was seen after two years (D/P: 0.56 ± 0.12 vs 0.55 ± 0.13). A centripetal pattern of change in D/P was observed. The ΔD/P had normal distribution and was inversely correlated with D/P at baseline ( r = -0.427, p < 0.005). Both results suggest a regression-to-mean phenomenon. The ΔD/P had no significant correlation with the total number of peritonitis episodes (Spearman r = 0.052, p = 0.74), but after severe peritonitis, affected patients had higher ΔD/P than patients who experienced no severe infection (0.040 ± 0.136 vs -0.032 ± 0.120, p < 0.05). For patients with no episodes of severe peritonitis (n = 47), ΔD/P was weakly correlated with baseline TGFβ level ( r = -0.506, p < 0.01). No correlation was seen between the levels of other fibrosing factors and change in peritoneal transport.ConclusionsOur findings suggest that the centripetal change of peritoneal transport probably reflects a regression-to-mean phenomenon. Peritoneal transport increases after severe peritonitis. The role of TGFβ levels in PDE with regard to longitudinal change in peritoneal transport requires further study.