Omentum

• The omentum is a large, fatty apron-like fold of peritoneum in the abdomen.
• It plays vital roles in immune defense, fat storage, and wound healing.
• The greater omentum hangs from the stomach and transverse colon, while the lesser omentum connects the stomach to the liver.
• It can be affected by various conditions, including inflammation, cysts, and metastatic cancer.
• Its unique properties make it a target for both diagnostic imaging and surgical intervention.

What is the Omentum?

The Omentum refers to a large, apron-like fold of visceral peritoneum that extends from the stomach and drapes over the intestines within the abdominal cavity. It is primarily composed of adipose tissue (fat), blood vessels, nerves, and lymphatic tissue. This structure is a crucial component of the abdominal anatomy, playing a protective and functional role. The omentum meaning and location are central to understanding its significance; it acts as a mobile, immunological organ that can migrate to sites of inflammation or injury.

Omentum Anatomy and Function

The omentum is broadly divided into two main parts: the greater omentum and the lesser omentum. The greater omentum is the larger and more prominent of the two. It originates from the greater curvature of the stomach and the first part of the duodenum, hanging down over the small intestine and colon like an apron before folding back up to attach to the transverse colon. This extensive structure gives it considerable mobility within the abdomen.

The lesser omentum, in contrast, is a smaller, double layer of peritoneum that extends from the lesser curvature of the stomach and the beginning of the duodenum to the liver. It forms the anterior wall of the omental bursa (lesser sac) and contains important structures like the hepatic artery, portal vein, and common bile duct.

The omentum function and anatomy are intrinsically linked to its physiological roles. Its primary functions include:

• Immune Defense: Rich in macrophages and lymphocytes, the omentum acts as an “abdominal policeman,” migrating to sites of infection or inflammation to wall off affected areas and prevent the spread of pathogens.
• Fat Storage: The abundant adipose tissue serves as a significant energy reserve for the body.
• Wound Healing and Adhesion Formation: It can adhere to injured organs, providing a source of blood supply and cells that aid in tissue repair. This characteristic, while beneficial for healing, can also lead to problematic adhesions post-surgery.
• Fluid Absorption: It helps to absorb peritoneal fluid, maintaining fluid balance within the abdominal cavity.

Conditions Affecting the Omentum

The omentum, despite its protective role, can be involved in various pathological processes. Diseases affecting the omentum can range from benign conditions to aggressive malignancies. Common conditions include:

• Omental Cysts: These are rare, fluid-filled sacs that can be congenital or acquired. They are often asymptomatic but can cause abdominal pain or a palpable mass if large.
• Omental Torsion: This occurs when the omentum twists on its vascular pedicle, leading to ischemia and necrosis. It typically presents with acute abdominal pain and can mimic appendicitis or cholecystitis.
• Omentitis: Inflammation of the omentum, which can be primary (rare) or secondary to other abdominal conditions like appendicitis, diverticulitis, or surgical trauma.
• Metastatic Cancer: The omentum is a common site for metastatic spread, particularly from gastrointestinal, ovarian, and breast cancers. Cancer cells can implant and grow on the omental surface, leading to omental caking or carcinomatosis, often associated with ascites (fluid accumulation in the abdomen). For instance, ovarian cancer frequently metastasizes to the omentum, with studies indicating omental involvement in approximately 70-80% of advanced cases (Source: American Cancer Society).
• Primary Omental Tumors: While rare, primary tumors such as leiomyosarcoma or liposarcoma can originate in the omentum.

Diagnosis of omental conditions often involves imaging techniques like ultrasound, CT scans, or MRI, which can reveal abnormalities in its size, texture, or the presence of masses or fluid. Treatment depends on the underlying condition, ranging from conservative management for mild inflammation to surgical resection for tumors or torsion.