Surface-Active Material in Peritoneal Effluent of CAPD Patients

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Abstract
The dialysis effluent of patients on continuous ambulatory peritoneal dialysis contains a surface-active material (SAM). This is composed of phospholipids; on thin-layer chromatography, this appears to be mainly phosphatidylcholine. Similar to the material described by Hills on the pleural surfaces of dogs (4), this SAM markedly reduces surface tension and promotes water repellency. The authors postulate that it may playa role in ultrafiltration and in the prevention of infection in CAPD patients. In the 10 years since its introduction, continuous ambulatory peritoneal dialysis (CAPD) has come into increased use to treat patients with chronic renal failure. Two problems stand in the way of the success of CAPD: infection of the peritoneum, and loss of ‘ultrafiltration’ -partitioning of water between the peritoneal cavity and the extracellular space (1, 2). The peritoneal membrane has not been studied extensively and we have a limited understanding of the exchange or non-exchange of water and other materials at this surface (3). Hills and co-workers (4) who demonstrated surface-active material (SAM) in washings of the pleural space of dogs have shown that biological SAM's, in addition to lowering surface tension, can lubricate a membrane as a boundary or adherent-type lubricant (4) and can confer water repellency to the surface (5,6). The present preliminary study was undertaken to determine whether the effluent dialysate of patients undergoing CAPD contained a similar surfaceactive material -a finding that would imply its presence on the peritoneal membrane. Secondly, if the dialysate contained SAM, whether that presence might be correlated with successful or complicated CAPD.