Omental bursa

The omental bursa, (also known as the lesser sac by opposition of the greater sac that corresponds to the general peritoneal cavity), is a peritoneal recess situated dorsal to the stomach and ventral to the pancreas and transverse colon. The epiploic foramen (foramen epiploicum; foramen of Winslow) is the passage of communication between the general peritoneal cavity and the omental bursa.

Boundaries and Communications

Ventral wall

• Liver: Particularly the caudate lobe, closely associated via the lesser omentum.

• Stomach: Specifically its dorsal surface, which forms a major portion of the ventral wall.

• Lesser Omentum: Extends from the liver to the lesser curvature of the stomach.

Dorsal wall

• Pancreas: Primarily the body, embedded in the dorsal wall.

• Left Kidney and Adrenal Gland: Sometimes contributing to the dorsal relation.

• Transverse Mesocolon and transverse colon.

Cranial Boundary

• Caudate process of the liver, particularly in ruminants where the omental bursa is deep and extensive.

• Diaphragm, via the coronary ligament and falciform ligament attachments.

Caudal Boundary

• Greater omentum: The dorsal and ventral leaves envelop the bursa caudally.

• This area can be extensive in species like the ox, where the greater omentum forms a large peritoneal sling.

Right Margin

• Epiploic foramen (Foramen of Winslow): The only natural communication between the omental bursa and the greater peritoneal cavity. Located dorsal to the hepatoduodenal ligament.

Left Margin

• Blind end closed by the gastrosplenic ligament and the spleen, particularly prominent in species like the dog and horse.

Subdivisions of the Omental Bursa

The omental bursa consists of a series of pouches or recesses to which the following terms are applied:

• Vestibule of omental bursa: The portion immediately inside the epiploic foramen.

• Main Bursa: The largest compartment, behind the stomach.

• Dorsal omental recess

• Opening of caudal recess

• Caudal omental recess: Extends into the greater omentum, especially well-developed in ruminants and carnivores.

• Splenic recess

Species Variations

Dog and Cat

• The omental bursa is relatively modest in extent.

• The greater omentum is not as large as in ruminants but still envelops portions of intestines.

• The bursa contains a small caudal recess.

Horse

• The bursa lies between the stomach and pancreas.

• The greater omentum is relatively thin and short, limiting the extent of the bursa.

• The epiploic foramen is clinically significant due to its role in internal herniation.

Ruminants (Cattle, Sheep, Goats)

• The omental bursa is highly developed.

• The greater omentum forms a deep "supraomental recess" that houses loops of intestines.

• It is suspended from the dorsal body wall and creates a large sling.

• The caudal recess of the omental bursa is particularly deep and clinically relevant (e.g., site for omental herniation or abscesses).

Pig

• Intermediate between carnivores and ruminants in omental development.

• The bursa is relatively well developed but smaller than in cattle.