Structures of the retroperitoneum

The retroperitoneum is the space just posterior to the peritoneal cavity and anterior to the paraspinous musculature (eg, psoas and quadratus lumborum, bilaterally). Superiorly, the retroperitoneum is bordered by the diaphragm, and inferiorly, it forms a natural extension into the pelvis. The retroperitoneum includes the bilateral kidneys and adrenal glands, perirenal fat, aorta, vena cava, and iliac vessels as well as the duodenum and pancreas. The ascending and descending colon are considered partially retroperitoneal.