Describe the location of lesser sac.
Lesser sac is the smaller part of the peritoneal cavity that lies behind the stomach and lesser omentum. It allows expansion and mobility of stomach.
What are the parts/subdivisions of lesser sac?
Lesser sac is divided into five parts:
- Vestibule: part of lesser sac immediately to the left of epiploic foramen. It is a constricted area between the left gastropancreatic fold of peritoneum (produced by left gastric artery) and right gastropancreatic fold (raised by common hepatic artery)
- Body: lies behind the lesser omentum and stomach
- Superior recess: part behind the caudate lobe of liver
- Splenic recess: between the gastrosplenic and lienorenal ligaments.
- Inferior recess: between the folds of greater omentum (is obliterated in adults).
Describe the boundaries of lesser sac.
Boundaries of lesser sac are as follows:
- Anterior wall is formed by (from above downwards):
- Lesser omentum
- Posterior surface of stomach covered by peritoneum.
- Anterior two layers of greater omentum
- Posterior wall consists of (from above downwards):
- Peritoneum covering the structures forming stomach bed.
- Posterior two layers of greater omentum.
- Superior border is formed by the peritoneum extending from the caudate lobe of liver to the diaphragm.
- Inferior border is formed by junction of anterior two layers of greater omentum with its posterior two layers.
- Right border is formed by (from above downwards:
- Left border is formed by (from above downwards):
- Gastrophrenic ligament
- Gastrosplenic and lienorenal ligament
- Left border of greater omentum
Applied Aspect
Pseudopancreatic cyst
The lesser sac may get filled with fluid as a result of perforation of gastric ulcer on the posterior wall of stomach or from an inflamed pancreas to form pseudopancreatic cyst.
What are the boundaries of epiploic foramen?
Epiploic foramen/Foramen of Winslow:
- Is the communication between the greater and lesser sac.
- Is located at the level of the T12 vertebra.
Its boundaries are:
- Anteriorly: free edge of lesser omentum containing within its layers:
- Bile duct (in front and to the right)
- Hepatic artery (in front and to the left0
- Portal vein (behind)
- Posteriorly: Inferior vena cava covered by peritoneum
- Superiorly: Caudate process of liver
- Inferiorly: 1st part of duodenum
Applied Aspect
A loop of intestine may herniate through the epiploic foramen into the lesser sac.
If the herniated loop is strangulated, the reduction is not possible through epiploic foramen as none of its boundaries can be incised due to important relations.
- Anteriorly in the free margin of lesser omentum are hepatic artery, portal vein and bile duct.
- Posteriorly is inferior vena cava.
- Superiorly is caudate lobe of liver
- Inferiorly is first part of duodenum
The alternate approach is along the cleavage between the greater omentum and transverse mesocolon. The intestinal loop is deflated and then the loop of small intestine is withdrawn through the epiploic foramen.
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