The epiploic (omental) foramen is a passageway between the greater peritoneal sac and the lesser peritoneal sac. It is located posterior to the hepatoduodenal ligament and the first part of the duodenum. The caudate lobe of the liver forms the posterior wall of the epiploic foramen. The aorta is retroperiteoneal, and it does not form a boundary of this foramen