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 characteristics.

DESIGN

Prospective, longitudinal, and comparative study.

SETTING

Outpatient continuous ambulatory peritoneal dialysis (CAPD) unit of a university medical center.

PARTICIPANTS

Seventy-one uninfected patients, treated for 0-156 months on CAPD, in stable condition were 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 peritoneal inflammation days/year and ultrafiltration/diffusion (mass transfer 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 content: ANAE, beta-glucuronidase, acid phosphatase) and immunohistochemical procedures (expression of membrane antigens, CD4, 11b, 11c, 14, 16, 25, 35, and 71).

RESULTS

The macrophage is the most frequently appearing 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 count remained stable over time (0.25-0.5 x 10(6)). Four of our patients showed a "transforming" change in these cells. Previous incidence of peritonitis and values of functional measurements did not correlate with cell count or expressions of macrophage function (lysosome enzyme content and percentage of cells expressing different membrane antigens).

CONCLUSION

There is difficulty interpreting the results on peritoneal effluent cells and their relationship with the incidence of peritonitis and functional characteristics of the peritoneum. No definite conclusions can be drawn other than the great interpatient and intrapatient variability. The presence of abnormal peritoneal cells with undetermined origin and function suggests the need for periodic studies of peritoneal effluent cells on long-term CAPD patients.