Anatomy, Abdomen and Pelvis: Foramen of Winslow (Omental Foramen, Epiploic Foramen)

Embryology

The embryonic foregut is suspended from the abdominal wall by ventral and dorsal mesentery. The liver develops within the ventral mesentery. The portion of the ventral mesentery between the liver and abdominal wall persists in the mature fetus as the falciform ligament. The segment of the ventral mesentery between the stomach and liver persists as the lesser omentum, including the hepatogastric and hepatoduodenal ligaments.

The part of the dorsal mesentery attached to the stomach persists as the greater omentum. The stomach shifts to the right during the first 90° of intestinal rotation, carrying the lesser omentum. The right side of the stomach and the lesser omentum lie against the posterior abdominal wall without fusion. The space posterior to the stomach constitutes the lesser sac.

Subsequent counterclockwise rotation of the midgut by 180° occurs around the axis of the superior mesenteric artery. The 3rd portion of the duodenum extends transversely across the peritoneal cavity, posterior to the superior mesenteric artery. This section of the duodenum and the pancreas becomes secondarily retroperitoneal, forming the posterior wall of the lesser sac.

The transverse colon also crosses the peritoneal cavity transversely but lies anterior to the superior mesenteric artery. Attachment of the greater omentum to the transverse colon completes the separation of the lesser sac from the greater sac, leaving only the small window at the free distal margin of the hepatoduodenal ligament, the foramen of Winslow.[5]

Surgical Considerations

Identification of the foramen of Winslow in the operating room is straightforward due to the pliability of viable tissue. Identification in stiff, nonpliable fixed tissue in the dissecting laboratory presents greater difficulty.

Localization of the foramen begins at the hepatogastric ligament. Following the lesser curvature of the stomach distally leads to the pylorus, where the lesser omentum becomes the hepatoduodenal ligament. Tracing the duodenum distally to the termination of the hepatoduodenal ligament permits insertion of a finger along the free edge of the ligament into the foramen of Winslow.

The cystic duct may be followed to the junction with the common hepatic duct, which continues along the course of the common bile duct within the hepatoduodenal ligament toward the foramen of Winslow. Mobilization of the hepatic flexure of the colon allows the 2nd portion of the duodenum to be traced proximally to the 1st portion of the duodenum, forming the inferior boundary of the foramen of Winslow.[6][7]

Clinical Significance

The foramen of Winslow is clinically notable for 2 reasons. First, the foramen constitutes a potential site for internal herniation, although hernias in this location are exceedingly rare.[8][9] Presenting symptoms typically reflect intermittent bowel obstruction and are nonspecific. Prior to the advent of modern imaging, diagnosis was frequently established only during laparotomy, and delays contributed to significant mortality. Computed tomography now facilitates diagnosis. Management consists of hernia reduction, with or without resection of nonviable viscera. Laparoscopic repair has also been reported.

The hepatic artery, portal vein, and common bile duct pass through the hepatoduodenal ligament immediately adjacent to the foramen of Winslow. This proximity allows rapid control of hepatic inflow in cases of uncontrolled hepatic hemorrhage. Insertion of the forefinger through the foramen permits compression of the vessels between the thumb and finger. For increased stability, 1 jaw of a vascular clamp may be placed through the foramen to compress the hepatic artery and portal vein.

Both techniques represent variations of the Pringle maneuver, first described by James Hogarth Pringle in 1908.[10] Pringle, born in Australia of Scottish descent, trained at the University of Edinburgh and was appointed surgeon at the Royal Infirmary of Glasgow in 1896. He gained recognition for the management of fractures, traumatic injuries, and radical amputations. Pringle’s 1908 publication, "Notes on the Arrest of Hepatic Hemorrhage due to Trauma," established him as a pioneer in trauma surgery.

Other Issues

The foramen of Winslow constitutes a distinct anatomical structure. Formation of this feature is readily explained by embryologic development. The foramen represents a rare site of clinical concern for the surgeon and serves as a notable landmark for identification in the dissection laboratory.