Lesser sac

Last revised by Heba Abdelmonem on 28 Mar 2023

The lesser sac or omental bursa is a potential peritoneal space within the abdomen, part of the peritoneal cavity

The lesser sac may be conceptualized as the space posterior to the lesser omentum, between the posterior wall of the stomach and the surface of the peritoneum that covers the anterior surface of the left kidney 1.

The epiploic foramen (of Winslow) is the only natural communication between greater and lesser sacs 3.

As the lesser sac is a peritoneal space, all of its boundaries are lined by visceral or parietal peritoneum 3. On the left side, the lesser sac is partially divided by a peritoneal fold over the left gastric fold, named pancreatogastric fold 3.

  • anterior

    • lesser omentum

    • visceral peritoneum along the posterior surface of the stomach

    • gastrocolic omentum (between greater curvature of the stomach and transverse colon)

  • left lateral

  • right lateral

  • posterior

    • visceral/parietal peritoneum that covers the diaphragm, pancreas, left kidney/adrenal gland, and duodenum

    • transverse mesocolon (between the transverse colon and anterior surface of the pancreas)

  • superior

    • peritoneum covering the caudate lobe of the liver

  • superior (hepatic) recess - between caudate lobe of liver and diaphragm; it is partially separated from splenic recess by gastropancreatic fold

  • splenic recess - between splenic ligaments and stomach

  • inferior (omental) recess - between the stomach and transverse colon

The lesser omentum is composed of two peritoneal ligaments that extend from the lesser curvature of the stomach and duodenal bulb to the liver, the gastrohepatic, and hepatoduodenal ligaments, respectively. During embryologic development, the rotation of the stomach relative to the liver causes redundancy in the mesentery about the stomach. 

As the greater curvature of the stomach rotates anterolaterally, a recess is formed between the redundant dorsal peritoneal ligament connecting the greater curvature of the stomach to the dorsal abdominal wall. Simultaneously, the lesser curvature of the stomach rotates posteromedially, and the ventral peritoneal ligament between stomach and liver becomes the lesser omentum, an incomplete boundary separating the main peritoneal cavity (greater sac) from the posterior recess (lesser sac). 

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Figure 2
    Drag here to reorder.
  • Case 2: lesser sac collection due to perforated peptic ulcer
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.