CELL-POPULATIONS PRESENT IN THE NOCTURNAL PERITONEAL EFFLUENT OF PATIENTS ON CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS AND THEIR RELATIONSHIP WITH PERITONEAL FUNCTION AND INCIDENCE OF PERITONITIS

Objective: To study the relationship between peritoneal effluent cells and infection rate and to relate this population with functional char acteristics. Design: Prospective, longitudinal, and comparative study. Setting: Outpatient continuous ambulatory peritoneal dialysis (CAPD) unit of a university medical center. Participants:Seventy-one uninfect ed patients, treated for 0 - 156 months on CAPD, in stable condition w ere studied (33 female, 38 male). Interventions: Nocturnal peritoneal effluent (NPE) was drained with EDTA (2.5 mmol/L) at 37-degrees-C and centrifuged at 2500 rpm for 9 minutes. Measurements: Accumulated perit oneal inflammation days/year and ultrafiltration/diffusion (mass trans fer coefficients (MTCs) for small molecules) capacities were recorded. Cellular count (cells/night) was performed using a Neubauer chamber. Macrophage function was assessed by cytochemical (lysosomal enzyme con tent: ANAE, beta-glucuronidase, acid phosphatase) and immunohistochemi cal procedures (expression of membrane antigens, CD4, 11b, 11c, 14, 16 , 25, 35, and 71). Results: The macrophage is the most frequently appe aring cell in the NPE. Cell count decreases over time on CAPD (from 20 x 10(6) to 5 x 10(6) after the first year). Intrapatient variability was low, but interpatient differences were marked. Mesothelial cell co unt remained stable over time (0.25 - 0.5 X 10(6)). Four of our patien ts showed a ''transforming'' change in these cells. Previous incidence of peritonitis and values of functional measurements did not correlat e with cell count or expressions of macrophage function (lysosome enzy me content and percentage of cells expressing different membrane antig ens). Conclusion: There is difficulty interpreting the results on peri toneal effluent cells and their relationship with the incidence of per itonitis and functional characteristics of the peritoneum. No definite conclusions can be drawn other than the great interpatient and intrap atient variability. The presence of abnormal peritoneal cells with und etermined origin and function suggests the need for periodic studies o f peritoneal effluent cells on long-term CAPD patients.