Location and Communication
A probe passed through the epiploic foramen enters directly into the vestibule of the lesser sac (vestibulum bursae omentalis). This vestibule represents the rightmost part of the lesser sac, bounded superiorly by the caudate lobe of the liver, inferiorly by the duodenum, and posteriorly by the parietal peritoneum covering the inferior vena cava.
The lesser sac is a slit-like space located posterior to the stomach, forming the most isolated compartment of the supramesocolic compartment of the peritoneal cavity. The epiploic foramen serves as the sole natural communication between the greater peritoneal cavity and the lesser sac.
Anatomical Borders of the Epiploic Foramen
The foramen has the following clear anatomical boundaries:
- Hepatoduodenal ligament (lig. hepatoduodenale) — forms the anterior boundary. This ligament is the free right edge of the lesser omentum, extending between the porta hepatis and the superior part of the duodenal bulb.
- Parietal peritoneum and hepatorenal ligament (lig. hepatorenale) — form the posterior boundary, covering the inferior vena cava (v. cava inferior).
- Caudate lobe of the liver (lobus caudatus) — forms the superior boundary.
- Duodenorenal ligament (lig. duodenorenale) and the superior part of the duodenum (pars superior duodeni) — form the inferior boundary. The duodenorenal ligament is a broad peritoneal fold between the descending duodenum and the right kidney.
Topography of Adjacent Structures
The hepatoduodenal ligament transmits the common bile duct, the common hepatic and cystic ducts, and the proper hepatic artery; posterior to these structures lies the portal vein (v. portae). Lymph nodes and anterior/posterior hepatic nerve plexuses are also found within this ligament.
Clinical and Surgical Significance
The epiploic foramen plays a critical role in pathology and surgical procedures:
- Containment of Inflammation: During fibrinous peritonitis, peritoneal surfaces can rapidly adhere. Consequently, the epiploic foramen may become sealed by adhesions, completely isolating the lesser sac from the general peritoneal cavity. Purulent exudates from a perforated gastric ulcer or acute pancreatitis can thus be contained within the lesser sac.
- Spread of Infection: Conversely, purulent exudates from primary sources like an inflamed appendix or gallbladder can spread along peritoneal pathways into the lesser sac.
- Temporary Vascular Clamping (Pringle Maneuver): During hepatic hemorrhage, a surgeon's index finger can be inserted into the epiploic foramen, allowing the hepatoduodenal ligament to be compressed between the finger and thumb to temporarily occlude hepatic blood flow.
- Drainage: During biliary tract surgery (e.g., following cholecystectomy), corrugated drains or gauzes may be placed near the gallbladder bed and the epiploic foramen if indicated.
Relationship with the Lesser Sac (Omental Bursa)
The lesser sac lies posterior to the stomach. Its walls are formed by:
- Anterior wall: Posterior wall of the stomach, lesser omentum, and gastrocolic ligament (lig. gastrocolicum).
- Posterior wall: Parietal peritoneum overlying the abdominal aorta, inferior vena cava, left suprarenal gland, left kidney, and pancreas.
- Superior wall: Caudate lobe of the liver and partly the diaphragm.
- Inferior wall: Transverse colon and its mesentery (mesocolon transversum).
- Left wall: Spleen and its ligaments (splenorenal and gastrosplenic ligaments).
If the epiploic foramen is obliterated, surgical access to the lesser sac is achieved by dividing the gastrocolic ligament or entering through the transverse mesocolon.