The importance of the peritoneal microcirculation is dependent on its use as an exchange organ, and this chapter will focus on those aspects of the transport barrier that affect the use of the peritoneal cavity in therapy. Therapy can be divided into two broad categories: (a) removal of waste metabolites and water by peritoneal dialysis from the body of a renal failure patient and (b) regional drug delivery, exemplified by intraperitoneal (IP) chemotherapy for metastatic ovarian or colorectal cancer. Whereas the goals of intraperitoneal chemotherapy are different from those of peritoneal dialysis, the transport mechanisms are basically the same. In intraperitoneal chemotherapy drugs are dissolved within a 2- to 3-L solution of dialysis fluid, which is instilled into the peritoneal cavity and allowed to absorb into the surrounding tissue. While in the cavity, the drugs diffuse across the peritoneum, through the tissue space, and into the blood vessels. A prime concern is maximizing the concentration in the targeted peritoneal metastases. In contrast, the goal of dialysis is to maximize transfer of water and solutes from the blood of anephric patients to the solution in the cavity. As illustrated in Figure 1, blood circulates through microvessels in the tissue below the peritoneum, and solutes and water must transport across the endothelium of the capillary, through the tissue interstitium, and across the peritoneum to the dialysis fluid, which is drained every 2 to 6 hours and replaced with fresh solution.
This functional view of the peritoneal microcirculation calls for an integrative approach that includes discussion of the lymphatic drainage of the cavity, the microvasculature, the interstitium surrounding the microvasculature, and the anatomic peritoneum. The system elements are made up of cells that are highly reactive to immunologic stimuli and which in turn affect transport across the peritoneum. In addition to the elements of the transport system, the area of contact between a solution in the peritoneal cavity and the tissue determines the route of absorption, metabolism, and rate of transfer. Each of these elements will be integrated to provide a conceptual model of the transport of solutes and water across the peritoneum.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.