Omentum and Metastatic Ovarian Cancer

A Curtain of Fat That Drapes Over Your Abdominal Organs

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Ovarian Cancer. Tetra Images / Getty Images

The omentum is a large fatty structure which literally hangs off the middle of your colon and drapes over the intestines inside the abdomen. Sometimes ovarian cancer spreads to the omentum. 

Anatomy and Structure of the Omentum

The omentum is a two-layered structure that is like a parachute, covering and surrounding the organs of the abdominal cavity. Its consistency is somewhere between that of lumpy linen and jello.

The omentum is broken down into two parts, which in adults are mostly fused together.

  • The greater omentum: hangs down from the stomach
  • The lesser omentum: hangs down from the liver

Purpose and Function of the Omentum

It is not clear why the omentum was designed as part of the human body, but it does reach every organ in the abdomen. So, it may act as a bandage in cases of bad infection or intestinal rupture, as it drapes over and attaches itself to areas of inflammation. 

Some other possible functions include:

  • Maintaining the positions of organs in the abdomen, including keeping the intestines and stomach near the liver
  • Acting as a storage depot for fat (see abdominal obesity below)

The Omentum and Ovarian Cancer Metastases

The omentum is important in ovarian cancer because it has a lot of tiny blood vessels. So cancer cells that have broken away from the ovary like to implant and grow there—this is known as omental metastasis.

The omentum also has a rich supply of lymphatic or immune areas known as "milky spots."

The omentum becomes very important in advanced ovarian cancer when debulking or cytoreduction surgeries are performed. These surgeries are done to remove as much cancer as possible, so there is less cancer left to treat with chemotherapy.

When much of the cancer is removed surgically, there is a greater chance that chemotherapy will be able to get rid of the leftover cancer cells before they become resistant to the chemotherapy medications.

Understanding the structure of the omentum makes is easier to understand why this debulking surgery in ovarian cancer is so difficult. It is a tedious and time-consuming surgery that takes great precision, as small clusters of cancer cells can be interspersed throughout the blood-vessel-rich omentum.

In addition, in order to get optimal cytoreduction, the surgery can take many hours. Another challenge is that the surgical time may be limited by a patient's inability to withstand an extended surgery under general anesthesia.  

Other Conditions Involving the Omentum

Several other conditions are related to the structure and function of the omentum:

  • Abdominal obesity: The omentum acts as a storage area for fat. When there is excessive storage of fat in the omentum, people develop an apple shaped body form known as abdominal obesity. This is referred to by many people as belly fat. Abdominal fat is one of the risk factors for metabolic syndrome. People with this syndrome are at a higher risk of developing heart disease.
  • Adhesions: Abdominal adhesions or scar tissue that forms throughout the omentum in response to abdominal surgery, infections, or inflammatory conditions involving the omentum can be a very serious condition. In fact, it is a common cause of emergency abdominal surgery for bowel obstructions and can also be a cause of infertility and chronic pain.

Sources:

Koppe MJ, Nagtegaal ID, de Wilt JH, Ceelen WP. Recent insights into the pathophysiology of omental metastases. J Surg Oncol. 2014 Nov;110(6):670-5.

Sorensen EW, Gerber SA, Sedlacek AL,  Rybalko VY, Chan VM, Lord EM. Omental immune aggregates and tumor metastasis within the peritoneal cavityImmunol Res. 2009. 45(2-3):185-94.

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