Peritoneal macrophage infiltration is correlated with baseline peritoneal solute transport rate in peritoneal dialysis patients

Background. High baseline peritoneal solute transport rate is reportedly associated with reduced patient and technique survival in continuous peritoneal dialysis (PD) patients. However, the determinants of baseline peritoneal solute transport rate remain uncertain. The aim of this study was to investigate the relationship between peritoneal local inflammation, angiogenesis and systemic inflammation and baseline peritoneal permeability. Methods. Peritoneal biopsy specimens from 42 pre-dialysis uraemic patients and 11 control individuals were investigated. Immunohistochemistry for CD68-positive macrophages, chymase- and tryptase-positive mast cells, interleukin-6 (IL-6)-positive cells, CD3-positive T cells, CD20-positive B cells, neutrophils and CD31- and pathologische anatomie Leiden-endothelium (PAL-E)-positive blood vessels in the peritoneum was performed. Baseline dialysate-to-plasma ratio for creatinine (D/P Cr) was determined within 6 months of PD induction. Clinical and laboratory parameters were measured at the time of peritoneal biopsy. Factors associated with peritoneal permeability were assessed by multiple linear regression analysis. Results. Pre-dialysis uraemic peritoneum showed infiltration by CD68-positive macrophages, and mast cells, as compared with controls. Baseline D/P Cr was correlated with density of CD68-positive macrophages (P < 0.001), IL-6-positive cells (P < 0.001), CD31-positive (P < 0.05) and PAL-E-positive blood vessels (P < 0.05) and serum albumin (P < 0.05). However, baseline peritoneal permeability was not correlated with infiltration by mast cells, B cells, T cells, neutrophils, serum C-reactive protein or other clinical factors. On multiple linear regression analysis, the number of CD68-positive macrophages in peritoneum was an independent predictor for baseline peritoneal permeability (P = 0.009). Conclusions. Peritoneal macrophage infiltration is predominant in uraemic patients and is an important factor in predicting baseline peritoneal permeability.