The Lesser Sac (Omental Bursa)
The lesser sac is an extensive, irregular peritoneal pouch located posterior to the stomach and the lesser omentum. It allows the stomach to move freely against the structures of the posterior abdominal wall.
Anatomical Boundaries
- Anterior: Posterior wall of the stomach and the lesser omentum.
- Posterior: Pancreas, left kidney, left adrenal gland, and the diaphragm.
- Superior: Liver (caudate lobe).
- Inferior: Transverse mesocolon.
Communication: The Epiploic Foramen
The lesser sac communicates with the greater sac via the Epiploic Foramen (Foramen of Winslow).
| Direction | Boundary of Epiploic Foramen |
|---|---|
| Anterior | Hepatoduodenal ligament (containing the portal triad). |
| Posterior | Inferior Vena Cava (IVC). |
| Superior | Caudate lobe of the liver. |
| Inferior | First part of the duodenum. |
High-Yield Exam Pearl:
Because the portal triad (common bile duct, hepatic artery, and portal vein) lies anterior to the epiploic foramen, an actively bleeding vessel in this region can be controlled by inserting a finger into the foramen and clamping the hepatoduodenal ligament (the Pringle Maneuver).