Peritoneal

Peritoneal refers to the peritoneum, the serous membrane that lines the abdominal cavity and covers most abdominal viscera. The peritoneum has two continuous layers: the parietal peritoneum lining the inner surfaces of the abdominal and pelvic walls, and the visceral peritoneum covering the external surfaces of most abdominal organs. The peritoneal cavity is a potential space containing a small amount of lubricating serous fluid that reduces friction during movement.

The peritoneum forms folds and structures that support and connect organs, including mesenteries, omenta, and ligaments. These folds route blood vessels, nerves, and lymphatics to the organs and help compartmentalize the abdomen. Distinctions are made between intraperitoneal organs, which are largely enveloped by visceral peritoneum and suspended by a mesentery, and retroperitoneal organs that lie behind the peritoneal cavity.

Functions of the peritoneum include providing lubrication to minimize friction between organs, offering mechanical support, and housing immune cells such as peritoneal macrophages. The peritoneal cavity can participate in fluid and protein exchange and can accommodate small fluid shifts without compromising organ function.

Clinical relevance: peritonitis is inflammation of the peritoneum, often due to infection or irritation. Ascites is the buildup of fluid within the peritoneal cavity, associated with liver disease, cancer, or heart failure. Peritoneal dialysis uses the peritoneal membrane as a dialysis surface to remove waste products from the blood. Metastatic spread within the peritoneal cavity is known as peritoneal carcinomatosis.

Etymology: the term derives from Greek peritoneon, meaning “stretched over.”