ROLE OF LYMPHATICS IN PERITONEAL-DIALYSIS

There is a renewed interest in understanding the precise role of lymph atics in the ultrafiltration kinetics during peritoneal dialysis. In t he normal state, lymphatics draining the peritoneal cavity are the pri ncipal means of removal of intraperitoneal isosmotic fluid and macromo lecules. During a hypertonic peritoneal dialysis exchange, after peak intraperitoneal volume is achieved, fluid removal proceeds at an almos t linear rate, causing intraperitoneal fluid volume to reduce. The iso smotic fluid removal from the peritoneal cavity could occur through th e microcirculatory capillaries or through the lymphatic capillaries dr aining the peritoneal cavity. Animal and human studies suggest that th is fluid loss occurs primarily through lymphatics. The two indirect me thods of lymph flow measurements, plasma appearance and peritoneal dis appearance of tracer colloid, show conflicting results. Although direc t measurement of lymph flow rates through cannulation of mediastinal l ymph vessels in animals suggests a significant flow through the lymph channels in response to intraperitoneal fluid instillation, lymph flow modification at the lymph node level may prevent use of this techniqu e to assess the precise role played by lymphatics in fluid kinetics du ring peritoneal dialysis. By analogy with ascites and by extrapolation from previous studies of drain volumes after infusion of isotonic and hypertonic solutions, the average daily lymph absorption rate during CAPD may be predicted to be at least 1 liter per day.