OMENTUM – Anatomy, Pathological conditions and

Surgical Importance

• OMENTUM is a fold of peritoneum extending from the stomach to adjacent abdominal organs.

• Aristotle (384-322 B.C.) described omentum as a warm fatty material attached to stomach which speeds digestion by its warmth

• Rutherford Morison developed the concept of the omentum as an "abdominal policeman"

Anatomy• Embryology of

peritoneum

• Omentum arises from dorsal and ventral mesenteries

• Stomach rotates by 90 degree to have lesser curvature on right and greater curvature on left

• Most of the ventral mesentery is reabsorbed the one persisting from ligamentum venosum, porta hepatis, proximal duodenum and lesser curvature is the lesser omentum

Greater omentum develops from dorsal mesogastrium

Greater omentum

• The greater omentum is a large fold of visceral peritoneum that hangs down from the stomach. It extends from the greater curvature of the stomach, passing in front of the small intestines and reflects on itself to ascend to the transverse colon before reaching to the posterior abdominal wall.

• Divided into two parts• The gastrocolic ligament extends between the

first part of the duodenum and great curvature of the stomach to the transverse colon. It contains the right and left gastroepiploic vessels

• The fat apron which hangs from the transverse colon to the free peritoneal cavity

• Arterial supply - right and left gastroepiploic arteries which anastomose and form the arc of Barkow.

• Venous drainage into portal system

• Lymphatics - two draining pathways

1. subpyloric nodes2. splenic nodes• Some studies reported

communication between the lymphatics of the omentum and the stomach

• Rich lymphatic vessels help in removing metabolic waste and excess fluid, destroying toxic substances, and fighting disease.

Lesser omentum

• a double-layered entity suspended between the lesser curvature of the stomach and the proximal ½ inch (2 cm) of the first part of the duodenum inferiorly and the porta hepatis and the fissure of the ligamentum venosum superiorly

• divided into two ligaments: the hepatogastric and the hepatoduodenal

• Contains the hepatic triad, branches of the anterior vagus nerve, some lymph nodes, and the right and left gastric arteries.

Lesser sac or Omental bursa• potential space behind the

stomach• It is demarcated anteriorly by

the quadrate lobe of the liver, the stomach, lesser omentum and gastrocolic ligament. Posteriorly it is marked by the pancreas. Its left lateral margin is made by the left kidney and adrenal gland. Its boundary on the right is made by the epiploic foramen and lesser omentum

Epiploic foramen • Also called foramen of Winslow• found just below the neck of the

gallbladder. • This foramen is bound anteriorly

by the right, free border of the duodenohepatic ligament, the fold forming the right termination of the lesser omentum, between the two layers of which are the hepatic artery, the portal vein, and the hepatic duct. It bound posteriorly by the inferior vena cava, which is covered by the peritoneum. Superiorly, it is bound by the caudate lobe of the liver and inferiorly, by the first portion of the duodenum and the hepatic artery

Pathological conditions of Omentum

Omental cysts• Etiology – obstructed omental

lymphatic channels• Unilocular or Multilocular • Asymptomatic or some times

mass palpable per abdomen• Complications – Torsion,

Infracts & rupture• Diagnosed by CT which shows

fluid filled, complex, cystic mass with septations

• Treatment- local excision

Omental torsion and infraction

• Due to axial twisting along its long axis• If twist is thight enough or venous obstruction is of

sufficient duration arterial in flow is compromised leadind to infraction and necrosis

• Two type 1)Primary- No cause usually on right side 2)Secondary – associated with other conditions like hernia, adhesions, tumors • Common in men seen in 4th and 5th decades

• Symptoms – abdominal pain usually on right side, nausea and vomiting in some cases

• o/e – localized abdominal tenderness, guarding present

• Differential diagnosis – should be differentiated from other rt sided abdominal pain like acute appendicitis, cholecytitis and twisted ovarian cysts

• Diagnosis is made by CT which shows omental mass

• Treatment – laprotomy and resection of involved omentum and correction of any related conditions

• Omental neoplasms• Usually rare and of soft tissue in origin• Mostly metastasis that has spread

transperitoneally from intra-abdominal cancer

Functions of Omentum

• Deposition of fat in form of adipose tissue• Immunity has milky spots which are macrophage

collections• Isolation of wound and infection• It limits intraperitoneal infection spread and are many

times found to encircle the concerned areas of trauma or infection

• Edema Absorption - lymphatic system has an enormous capacity to absorb edema fluid

• Stem cells

Clinical importance of Omentum

• Drainage – collection in anterior aspect of stomach is collected in greater sac and collection below liver is collected in leesser sac through epiploic foramen

• Surgical approach to retro peritoneum

• Division of either left or right gastroepiploic artery and vasa recta along the greater curvature of stomach with mobilization of omentum from transverse colon allows development of a vascularised omental pedicle flap

• Used to cover chest and mediastinal wounds after chest wall resection

• Used to prevent small intestine from entering pelvis after abdominal perineal resection thus preventing radiation enterits due to radio therapy for rectal cancer

• Formation of dense adhesions between omentum and sites of perforation or inflammation thus facilitates use as patch for duodenal perforation for ulcer disease known as Graham patch

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