Root of the small-bowel mesentery: Correlative anatomy and CT features of pathologic conditions

The root of the small-bowel mesentery (SBM) is an important peritoneal fold that is contiguous to other peritoneal ligaments and mesocolons. Several p athologic conditions can occur in the SBM itself, and diseases that spread through the connections from adjacent organs frequently involve it. The roo t of the SBM is contiguous to the hepatoduodenal ligament around the superi or mesenteric vein (SMV) and contiguous to the right side of the transverse mesocolon around the gastrocolic trunk. The inferior mesenteric vein, whic h is a landmark of the descending mesocolon, runs along the left side of th e root of the SBM. Malignant neoplasms can spread to the SBM by means of di rect extension, extension along the neural plexus, extension along neighbor ing ligaments, or extension along lymphatic vessels. Inflammatory condition s such as pancreatitis and perforation of a jejunal diverticulum can also s pread to the SBM. Anomalies that can occur in the SBM include rotation anom alies and internal hernia. Vascular lesions of the SBM include thrombosis o f the superior mesenteric artery (SMA), acute SMV thrombosis, SMA dissectio n, arterioportal fistula, and portal venous gas. Other pathologic condition s that can occur in the SBM are edema or congestion, mesenteric tear, mesen teric panniculitis, and tumors or tumorlike lesions.