Lymphatic Absorption in CAPD Patients with Loss of Ultrafiltration Capacity

Abstract

During continuous ambulatory peritoneal dialysis (CAPD) treatment, loss of ultrafiltration capacity (UFC) is a common complication that can be associated with increased peritoneal fluid absorption rate. The aim of the present study was to investigate the relative importance of lymphatic absorption for total peritoneal fluid absorption in patients with permanent loss of UFC associated with a high peritoneal absorption rate (K_E, ml/min; high-K_E group, n = 4). Clinically stable CAPD patients (n = 23) as well as patients with loss of UFC associated with increased diffusive mass transport coefficients (K_BD, ml/min; high-K_BD group, n = 8) served as control groups. The patients were investigated with a 6-hour dwell study with 3.86% glucose solution. The total fluid absorption rate was estimated by the disappearance rate (K_E) of ¹³¹I-radioiodinated human serum albumin (RISA) from the peritoneal cavity, and the lymphatic absorption rate was estimated by the rate of RISA appearance in plasma (K_PP, ml/min). The values of K_E and K_PP in the high-K_E group (4.65 ± 0.93 and 0.42 ± 0.31 ml/min, respectively) were markedly higher than in the clinically stable CAPD patients (1.77 ± 0.60 and 0.15 ± 0.06 ml/min, respectively; both p E group). In the high-K_BD group, K_E was lower (2.19 ± 0.38 ml/min, p E group, whereas K_PP was similar (0.26 ± 0.09 ml/min, NS). The fraction of K_E which could be accounted for by K_PP was on average only 9 + 5% in the high-K_E group and did not differ from the fractions in the clinically stable patients or in the high-K_BD group (9 ± 5 and 12 ± 4%, respectively). In 5 patients in whom plasma RISA activity was measured for 24 h from the beginning of the 6-hour dwell study, a continuous increase of the RISA level in plasma was observed during this time period. We conclude that although K_PP was increased in patients with UFC loss associated with high K_E, it accounted for only a minor part of K_E. Furthermore, the relatively slow but prolonged appearance of RISA in plasma indicates that the interstitial compartment may serve as a reservoir of macromolecules which are slowly absorbed by local lymphatics. The present study supports previous findings that direct lymphatic absorption is only of relatively minor importance for the fluid absorption in peritoneal dialysis.