Retroperitoneale

The retroperitoneum is the anatomical space in the abdomen and pelvis situated behind the peritoneum. It extends from the diaphragmatic hiatus to the pelvic brim and contains a set of organs and connective tissues that are not enclosed within a peritoneal cavity.

The peritoneum lines the abdominal cavity but covers only the anterior surface of most retroperitoneal organs. The space is commonly subdivided by fascial planes into the perirenal or perinephric space (around the kidneys and adrenal glands within Gerota’s fascia), the anterior pararenal space (between the anterior renal fascia and the peritoneum; it contains the pancreas, parts of the duodenum, and portions of the colon), and the posterior pararenal space (between the posterior renal fascia and the transversalis fascia; it contains fat, vessels, and nerves). These compartments help delineate the spread of disease and guide surgical approaches.

Contents and development: The retroperitoneal organs include the kidneys, adrenal glands, and ureters (primary retroperitoneal). Other organs are secondarily retroperitoneal, meaning they were initially intraperitoneal during development but become fixed behind the peritoneum with time; these include the pancreas (head and body), duodenum (parts II–IV), and the ascending and descending colon. The tail of the pancreas is intraperitoneal. The retroperitoneum also contains major vessels, such as the aorta and inferior vena cava, as well as associated lymphatics and nerves.

Clinical relevance: Its location behind the peritoneum affects how diseases spread and are detected, with imaging (CT or MRI) and surgical planning often focusing on fascial compartments and retroperitoneal planes.