What are the compartments of the retroperitoneum and their contents?
The anterior pararenal space, perirenal space, and posterior pararenal space are the main retroperitoneal compartments, which are separated from each other by fascial planes. The anterior pararenal space, which contains the ascending colon, descending colon, second through fourth portions of the duodenum, and pancreas, is located anterior to the anterior renal fascia and medial to the lateroconal fascia and is contiguous across the midline. The bilateral perirenal (or perinephric) spaces contain the kidneys, renal pelves and proximal ureters, adrenal glands, and fat and are located between the anterior and posterior renal fascia. The posterior pararenal spaces contain fat are located posterior to the posterior renal fascia and external to the lateroconal fascia, and are contiguous with the properitoneal fat of the abdomen. The retroperitoneal fascial planes are not composed of single membranes but are laminated. As such, although they may serve as barriers to disease spread, these potentially expansile fascial planes may alternatively serve as conduits of disease spread to other compartments in the abdomen and pelvis.