A distributed model of bidirectional protein transport during peritoneal fluid absorption.

The present article provides a theoretical description of the changes of interstitial hydrostatic pressure, tissue hydration, and protein distribution in the tissue during a peritoneal dwell with isotonic fluid. The mathematical model is based on the concept of uniformly distributed capillary and lymphatic systems within a deformable, porous tissue. Protein transport was analyzed for diffusive and convective transport of serum albumin (SA) and radiolabeled albumin (RISA; added to dialysis fluid) using Darcy's law for fluid flux through the tissue and the two-pore theory for water and protein flow across blood capillary walls. Numerical results showed a local increase of interstitial hydrostatic pressure and tissue hydration over physiologic level in the tissue layer close to the peritoneal surface. The water inflow to the tissue displaced interstitial SA into the deeper tissue layers and yielded RISA accumulation in the tissue at a concentration locally higher than that in the dialysis fluid. The description of water flow agreed with clinical data, but yielded a higher-than-expected hydrostatic pressure in the deep tissue layers. The steady-state rates of fluid and RISA absorption from the peritoneal cavity, but not of SA clearance, agreed with the clinical data.