Greater sac anatomy

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Greater Sac - Anatomy

Definition and Overview

The peritoneal cavity is divided into two main subdivisions: the greater sac and the omental bursa (lesser sac). The greater sac constitutes the vast majority of the peritoneal cavity. It begins superiorly at the diaphragm and extends inferiorly into the pelvic cavity. It is entered once the parietal peritoneum has been penetrated.

Gray's Anatomy for Students, p. 363

The greater and lesser omentum divide the peritoneal cavity into the greater and lesser sacs. The lesser sac is contained behind the lesser and greater omentum, the stomach, and the transverse colon, and communicates with the greater sac through the foramen of Winslow (omental/epiploic foramen).

Sabiston Textbook of Surgery, p. 1447

Sagittal View - Greater Sac and Relations

Greater sac sagittal diagram showing diaphragm, liver, lesser omentum, stomach, greater omentum, transverse colon, small intestine, and the lesser sac (omental bursa) posteriorly

Fig. 4.54 - Greater and Lesser Sacs of the Peritoneal Cavity (Gray's Anatomy for Students)

Transverse Section - Omental Foramen and Boundaries

Transverse section showing continuity between greater sac, omental foramen, and lesser sac (omental bursa) with surrounding structures - portal vein, bile duct, hepatic artery, IVC, falciform ligament, stomach, spleen, kidneys

Fig. 4.55 - Transverse Section showing Continuity Between Greater and Lesser Sacs through the Omental (Epiploic) Foramen (Gray's Anatomy for Students)

Omental (Epiploic) Foramen - Boundaries

The omental foramen is the communication between the greater sac and the lesser sac. The structures bordering it (all covered with peritoneum) are:

Relation	Structure
Anterior	Portal vein, hepatic artery proper, bile duct (in the free edge of the lesser omentum)
Posterior	Inferior vena cava
Superior	Caudate lobe of the liver
Inferior	First part of the duodenum

Gray's Anatomy for Students, p. 363

Compartments of the Greater Sac

The transverse colon and its mesentery divide the greater sac into a supramesocolic and an inframesocolic compartment.

Diagram showing peritoneal cavity compartments - coronal view (A) and midsagittal view (B) - showing supramesocolic and inframesocolic spaces, paracolic gutters, lesser sac, mesenteries, and omentum

Fig. 21.47 - Division of Peritoneal Cavity (Grainger & Allison's Diagnostic Radiology)

1. Supramesocolic Compartment

(Diaphragm to transverse mesocolon)

Right supramesocolic space:

Right subphrenic space - over the diaphragmatic surface of the right lobe of liver; limited on the left by the falciform ligament and posteromedially by the right coronary ligament
Right subhepatic space (Morison's pouch / hepatorenal fossa) - between the liver and the right kidney; the most gravity-dependent space in the supine position; common site for fluid and abscess collection after biliary surgery

Left supramesocolic space (four intercommunicating compartments):

Left anterior perihepatic space - bounded by falciform ligament (right), liver surface (posteriorly), and diaphragm (anteriorly); affected by left lobe liver or gastric lesions
Left posterior perihepatic space (gastrohepatic recess) - posterior margin of the lateral segments of the left lobe; close to lesser curve of stomach and anterior duodenal wall
Left anterior subphrenic space - between anterior stomach wall and left hemidiaphragm; fluid here suggests gastric or splenic flexure perforation
Left posterior subphrenic / perisplenic space - posterior extension of the anterior subphrenic space

2. Inframesocolic Compartment

(Transverse mesocolon to pelvic rim)

Right infracolic space - the smaller of the two; terminates at the ileocaecal junction; bounded laterally by the ascending colon
Left infracolic space - larger; opens into the pelvis except where restricted by the sigmoid mesocolon; bounded laterally by the descending colon
Right paracolic gutter - alongside the ascending colon; freely continuous with the right perihepatic space superiorly and with the pelvic cavity inferiorly (important route for spread of infection and malignancy)
Left paracolic gutter - alongside the descending colon; cephalad continuation is partially restricted by the phrenicocolic ligament, limiting upward spread from the left side

3. Pelvic Peritoneal Cavity

Lateral paravesical spaces
Pouch of Douglas - rectouterine space (females) or rectovesical space (males); the most dependent portion of the entire peritoneal cavity in the erect posture
Grainger & Allison's Diagnostic Radiology, pp. 547-548

CT Peritoneogram - Greater Sac in Context

Sagittal CT peritoneogram showing lesser omentum, lesser sac, transverse mesocolon, greater omentum, small bowel mesentery, sigmoid mesentery, greater sac, and rectouterine pouch - L=liver, S=stomach, C=colon

Fig. 70.1 - CT peritoneogram illustrating mesenteries, greater sac, lesser sac, and omenta (Sabiston Textbook of Surgery)

Peritoneal Fluid Circulation

Peritoneal fluid circulates in a clockwise direction within the greater sac. The common sites where fluid (ascites, blood, pus) pools and where peritoneal implants are found are:

Rectovesical/rectouterine pouch (Pouch of Douglas) - most dependent in erect posture
Right paracolic gutter - most dependent in supine posture, connects freely with subhepatic space
Right subhepatic space (Morison's pouch)
Right subphrenic space
Left paracolic gutter (less free communication superiorly due to phrenicocolic ligament)

Sabiston Textbook of Surgery, p. 1447; Yamada's Textbook of Gastroenterology

Histology of the Peritoneum

The peritoneum (lining both greater and lesser sac) consists of:

Mesothelium - a single layer of simple cuboidal epithelium
Underlying mesenchymal cells

Functions include: protection of viscera, facilitation of smooth visceral movement, immunologic roles, and tissue repair/scar formation. The peritoneal surface area is very large, which facilitates both disease spread and therapeutic delivery (e.g., peritoneal dialysis, HIPEC).

Sabiston Textbook of Surgery, p. 1447

Clinical Relevance Summary

Feature	Clinical Significance
Morison's pouch (hepatorenal fossa)	First site of free fluid accumulation on FAST ultrasound in trauma
Pouch of Douglas	Palpable on PR/PV exam when fluid, pus, or tumour is present
Right paracolic gutter	Pathway for spread of appendicitis/peritonitis to right subphrenic space
Phrenicocolic ligament	Limits spread up the left paracolic gutter (contrast with right side)
Omental foramen	Bordered by portal triad anteriorly and IVC posteriorly; Pringle manoeuvre compresses it
Greater omentum	Acts as a "policeman of the abdomen" - walls off infection and perforations

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