Peritoneal dialysis: physiology, current applications and future directions.

The peritoneal dialysis system is a sophisticated dialyser. It probably represents a capillary kidney regulating the number of capillaries perfused, the nature of capillaries perfused, and the overall permeability of its membranes. Its sophistication far exceeds that available with extracorporeal man-made haemodialysis systems. However, because of limited pore area and inaccessible fluid film resistances, it will never be an efficient dialyser for small solute removal. One way to overcome this intrinsic inefficiency is to utilise CAPD which trades efficiency for time. Our first two years of experience with CAPD have answered many initial questions, at least in a preliminary fashion. The future of CAPD has exciting potential, but many questions remain.