Greater and lesser omenta: normal anatomy and pathologic processes.

The peritoneum is the largest serous membrane in the body and the one with the most complex structure. The omentum is a double-layered extension of the peritoneum that connects the stomach to adjacent organs. The peritoneal reflections form the greater and lesser omenta, and the natural flow of peritoneal fluid determines the route of spread of intraperitoneal fluid and consequently of disease processes within the abdominal cavity. The omenta serve both as boundaries for disease processes and as conduits for disease spread. The omenta are frequently involved by infectious, inflammatory, neoplastic, vascular, and traumatic processes. Computed tomography (CT) is a primary diagnostic method for evaluation of omental diseases, most of which may manifest with nonspecific clinical features. Multidetector CT with multiplanar reformation allows accurate examination of the complex anatomy of the peritoneal cavity, knowledge of which is the key to understanding the pathologic processes affecting the greater and lesser omenta. (c) RSNA, 2007.