Dialysate CA125 in stable CAPD patients: no relation with transport parameters.

We investigated dialysate CA125 concentrations (dCA125) and its possible relation to transport parameters in 67 stable CAPD patients. dCA125 can be regarded as a reflection of mesothelial cell mass or mesothelial cell turn-over. In every patient a standard peritoneal permeability analysis (SPA) was done. dCA125 was determined in the effluent of all SPA's. The examinations were done during a 4 h dwell with glucose 1.36%. In 29 tests dextran 70(milligrams) was added for fluid kinetics. dCA125 was positively related to age (p = 0.03) and negatively to the duration of CAPD (p = 0.0003). No correlation existed with peritonitis incidence (p = 0.21). Also, no relationship was present with the mass transfer area coefficient of creatinine, or with net ultrafiltration. The intrinsic permeability to macromolecules, expressed as the restriction coefficient (rc) was also not related to dCA125 (p = 0.14). Data on fluid kinetics showed that neither transcapillary ultrafiltration rate, effective lymphatic absorption rate, the change in intraperitoneal volume (delta IPV) nor glucose absorption were related to dCA125. A subgroup of patients (n = 20) had low CA125 values (< 11 U/ml). They were treated with CAPD for a longer period of time (23 vs 16 months, p = 0.02), and had a higher rc (2.59 vs 2.23, p < 0.0001). The relationship between low dCA125 and duration of CAPD can possibly be explained by vanishing of the mesothelial layer, as has been reported in patients on long-term CAPD. The higher rc of the low dCA125 group is probably also related to duration of CAPD, and not directly to the mesothelial cell mass, as the mesothelium is no osmotic barrier and because no pathophysiological mechanism can explain the relationship between a low mesothelial cell mass and a low permeability to macromolecules. It can be concluded that mesothelial cell mass is negatively related to the duration of CAPD treatment, but mesothelial cells are unlikely to play an important role in transport kinetics.