A distributed model of fluid and mass transfer in peritoneal dialysis.

A mathematical model has been developed to study peritoneal fluid and solute transfer. The model uses the concept of a distributed capillary system within the peritoneal tissue. The model accounts explicitly for transport across the capillary membrane, through interstitial tissue, and across the mesothelium. The capillary and mesothelial membranes are modeled using pore theory and a dual pathway (through pores and across cells) for fluid transfer. The nonperitoneal tissues are modeled as a single body pool. Lymphatic uptake from the peritoneal cavity is included. Model parameters were found from the literature and by simultaneously fitting experimental data for dialysate volume and dialysate concentrations of blood urea nitrogen, glucose, creatinine, and inulin. The model was also shown to predict concentration gradients within several tissues surrounding the peritoneal cavity. Variation of the model parameters revealed the importance of the mesothelial cell layer in peritoneal ultrafiltration. The results of model simulations indicate an initial transfer of fluid from the tissue space to the peritoneal cavity followed by transcapillary fluid transfer.