Lesser sac

The lesser sac or omental bursa is a potential peritoneal space within abdomen, part of the peritoneal cavity. It may be conceptualized as the space posterior to the lesser omentum, between the posterior wall of the stomach and surface of peritoneum which covers the anterior surface of the left kidney.1

The lesser omentum refers to the peritoneal ligaments extending from the lesser curvature of the stomach/duodenal bulb to the liver (gastrohepatic, hepatoduodenal ligaments). During embryologic development, the rotation of the stomach relative to the liver causes a 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 greater curvature of 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). 

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


As the lesser sac is a peritoneal space, all of its boundaries are lined by visceral or parietal peritoneum.

  • anterior
    • lesser omentum
    • visceral peritoneum along posterior stomach
    • gastrocolic omentum (between greater curvature of stomach and transverse colon)
  • left lateral
    • gastrosplenic and lienorenal ligaments
  • posterior
    • visceral/parietal peritoneum that covers diaphragm, pancreas, left kidney/adrenal gland, and duodenum
    • transverse mesocolon (between transverse colon and anterior surface of pancreas)
  • superior
    • peritoneum covering caudate lobe of the liver
Anatomy: Abdominopelvic
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Article information

rID: 33840
Section: Anatomy
Tag: refs
Synonyms or Alternate Spellings:
  • Omental bursa

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