Supracolic compartment

Greater omental sac

The intricate folding of the midgut and hindgut during embryological development has resulted in the convoluted nature of the peritoneal cavity. The greater omentum – double membranous layer of peritoneum extending inferiorly from the greater curvature of the stomach – covers the intestines before turning superiorly to attach to the transverse colon. All the structures deep to the greater omentum are therefore said to be in the greater omental sac (bursa); or simply, the greater sac.

Lesser omental sac

Since there is a greater omentum and corresponding omental sac, there is also a lesser omentum with its lesser omental sac. The lesser omental sac (bursa) lies deep to the lesser omentum, which is attached along the lesser curvature of the stomach and along the hepatic fissure of ligamentum venosum and the porta hepatis. This sac is limited anteriorly by the quadrate lobe of the liver, the gastrocolic ligament and the lesser omentum. The parietal peritoneum forms the posterior limit of the space.

Deep to this layer is the left suprarenal gland along with the superior part of the left kidney, the neck and body of the pancreas, and the diaphragm. Also related posteriorly are the abdominal aorta, celiac trunk and its branches, and the inferior phrenic arteries.

Superiorly, the lesser omental bursa continues into a superior recess which extends cranially between the esophagus and the inferior vena cava. To the left it is limited by the left kidney and the left adrenal gland. To understand the right limitations of the sac, recall the fact that the lesser omentum is divided into a gastrohepatic and a hepatoduodenal part. The hepatoduodenal part, which transmits the portal triad (hepatic artery proper, bile duct and hepatic portal vein), forms the right anterior border of the lesser omental bursa.

Also to the right, the inferior vena cava is located posteriorly, the superior part of the duodenum inferiorly, and the caudate process of the caudate lobe of the liver superiorly. These limitations form the epiploic foramen of Winslow, which allows communication between the lesser sac and the greater sac. Finally, the transverse mesocolon, which attaches to the mesocolic taenia of the transverse colon, limits the lesser omental bursa inferiorly.

Subphrenic space

The transverse colon has an additional function in dividing the peritoneal cavity. Its mesocolon serves as an anteroposterior divisive line that partitions the peritoneum into a supracolic and an infracolic compartment. In addition to the lesser omental bursa, the supracolic region houses subphrenic and subhepatic spaces. The subphrenic space lies immediately inferior to the diaphragm and superior to the liver.

It can be divided into a right and left subphrenic space by the falciform ligament of the liver. The right subphrenic space is limited posteriorly by the coronary ligament and relates directly to the anatomical right lobe of the liver (namely, the right lateral, anterior and superior parts).

The left subphrenic space is substantially larger than the right and has been described as having anterior and posterior segments. Overall, the left subphrenic space relates to the anterior parts of the cardia and fundus of the stomach, the spleen’s diaphragmatic region and the anterosuperior extent of the anatomical left lobe of the liver. It is restricted posteriorly by the left triangular ligament and inferomedially by the lienogastric, lienorenal and phrenicocolic ligaments. The latter three ligaments also aid in partially separating the subphrenic space from the left paracolic gutter.

Subhepatic space

Below the liver, but above the transverse mesocolon, are the subhepatic spaces of the abdomen. The pars descendens of the duodenum (the second or descending part) forms the medial extent of the right subhepatic space; also known as the hepatorenal pouch of Morrison. The lateral boundary is formed by the right lateral abdominal wall. Superiorly, the coronary ligament limits the space while the anterosuperior part of the upper pole of the right kidney forms the posterior boundary. The left subhepatic space or the lesser omental bursa communicates with the right subhepatic space via the epiploic foramen of Winslow.