Greater Sac

The greater sac is the largest and most prominent portion of the peritoneal cavity. It occupies the majority of the abdominopelvic space and extends from the diaphragm superiorly to the pelvic floor inferiorly. This compartment contains most of the abdominal organs and is subdivided by peritoneal reflections and mesenteries into functional spaces that guide the flow of peritoneal fluid and define anatomical relationships. The greater sac is continuous with the lesser sac (omental bursa) via the epiploic foramen, allowing communication between anterior and posterior peritoneal compartments.

Location and Boundaries

The greater sac spans the entire height of the peritoneal cavity and occupies the area anterior and lateral to the stomach and abdominal viscera.

Superior to Inferior Extent

• Superiorly: Diaphragm (including subphrenic spaces)
• Inferiorly: Pelvic cavity, down to rectouterine pouch in females or rectovesical pouch in males

Anterior and Posterior Boundaries

Boundary	Structure
Anterior	Parietal peritoneum of the anterior abdominal wall
Posterior	Posterior abdominal wall and retroperitoneal organs

Communication with the Lesser Sac

The lesser sac (omental bursa), located posterior to the stomach, communicates with the greater sac through the **epiploic (omental) foramen**, also known as the **foramen of Winslow**.

Epiploic Foramen Boundaries

• Anterior: Hepatoduodenal ligament (contains portal triad)
• Posterior: Inferior vena cava
• Superior: Caudate lobe of the liver
• Inferior: First part of the duodenum

Subdivision of the Greater Sac

The transverse colon and its mesocolon divide the greater sac into two primary compartments:

1. Supracolic Compartment

Located above the transverse mesocolon, this compartment contains:

• Liver
• Stomach
• Spleen
• Lesser omentum
• Portions of the diaphragm

2. Infracolic Compartment

Located below the transverse mesocolon, this compartment contains:

• Small intestine (jejunum and ileum)
• Ascending colon
• Descending colon
• Root of the mesentery

The infracolic compartment is further divided by the root of the mesentery into:

• Right infracolic space
• Left infracolic space

Paracolic Gutters

These are longitudinal channels formed by the lateral peritoneal reflections of the ascending and descending colon. They facilitate the movement of fluids and infections within the greater sac.

Paracolic Gutter	Location	Notes
Right	Lateral to ascending colon	Provides a pathway from pelvis to subhepatic space
Left	Lateral to descending colon	Limited superiorly by the phrenicocolic ligament

Dependent Spaces within the Greater Sac

1. Subphrenic Spaces

• Located between diaphragm and liver
• Right subphrenic space: Between liver and diaphragm, anterior to the coronary ligament
• Left subphrenic space: Between left lobe of liver and diaphragm

2. Hepatorenal Recess (Morison’s Pouch)

• Between liver and right kidney
• Most dependent space in supine patients — common site for fluid accumulation

3. Pelvic Pouches

These include:

• Rectouterine pouch (Pouch of Douglas): Between rectum and uterus (females)
• Rectovesical pouch: Between rectum and bladder (males)

Clinical Importance

Ascites

• Fluid collects in the dependent parts of the greater sac — pelvic pouches and hepatorenal recess

Peritonitis

• Inflammation can involve any area of the greater sac, with fluid and pus tracking through paracolic gutters

Peritoneal Carcinomatosis

• Malignant cells may seed along peritoneal surfaces, particularly in greater sac compartments

Surgical Access

• Knowledge of sac subdivisions is crucial for laparotomies, laparoscopy, and abscess drainage

Summary Table: Greater Sac Compartments

Region	Contents	Clinical Note
Supracolic compartment	Liver, stomach, spleen	Common site of subphrenic abscesses
Infracolic compartment	Small intestine, colon	Tracks fluid to pelvis
Right paracolic gutter	Along ascending colon	Infection route to Morison’s pouch
Left paracolic gutter	Along descending colon	Limited superiorly by ligament
Pelvic pouches	Rectouterine/rectovesical spaces	Most dependent in upright position