Longitudinal study of peritoneal membrane function in continuous ambulatory peritoneal dialysis: Relationship with peritonitis and fibrosing factors

Background: The 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. Patients: We studied 105 unselected CAPD patients, Average age at enrollmen t was 50.7 +/- 11.3 years. Methods: A PET was performed at enrollment. Peritoneal transport was expres sed as dialysate-to-plasma creatinine ratio at 4 hours (D/P). Fibrosing fac tors and mesothelial cell markers, including TGF beta, epidermal growth fac tor (EGF), platelet-derived growth factor (PDGF), hyaluronan, and cancer an tigen 125 (CA125), were measured in overnight peritoneal dialysate effluent (PDE). Patients were followed for two years. Peritonitis episodes were rec orded. Severe peritonitis was defined as an episode that required catheter removal or antibiotic therapy for more than 3 weeks. After two years, 75 pa tients were still alive and on CAPD. Results: The PET was repeated in 64 patients, of whom 35 were male and 9 ha d diabetes. The change in D/P over two years was represented as DeltaD/P. N o 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 DIP wa s observed, The DeltaD/P had normal distribution and was inversely correlat ed with D/P at baseline (r = -0,427, p < 0.005). Both results suggest a reg ression-to-mean phenomenon. The <Delta>D/P had no significant correlation w ith the total number of peritonitis episodes (Spearman r = 0.052, p = 0.74) , but after severe peritonitis, affected patients had higher DeltaD/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), <Delta>D/P was weakly correlated with baseline TGF beta level (r = -0 .506, p < 0.01). No correlation was seen between the levels of other fibros ing factors and change in peritoneal transport. Conclusions: Our findings suggest that the centripetal change of peritoneal transport probably reflects a regression-to-mean phenomenon. Peritoneal tr ansport increases after severe peritonitis. The role of TGF<beta> levels in PDE with regard to longitudinal change in peritoneal transport requires fu rther study.