What Is Omenta?
Omenta (plural) or omentum (singular) is a large layer of fatty tissue that envelops the organs in the abdominal cavity. Besides storing the fat, the omentum also plays an important role in immunity and tissue regeneration.
The omentum is essential for neovascularization (formation of new blood vessels), hemostasis (stops bleeding), healing, regeneration, and as a culture medium for cell and tissue cultivation.
The body has two types of omentum -
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Greater omentum that covers the small and large intestines.
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Lesser omentum that covers the lower stomach and the duodenum. It houses the left gastric vessels and their associated lymph nodes, portal vein, hepatic artery, and hepatic lymph nodes.
Both types of omentum are covered by the visceral peritoneum (inner lining of the abdomen that covers the outer surface of the abdominal organs); the order goes like this- internal organs are covered by omentum (fat), which is again covered by the visceral peritoneum.
Because of the omentum’s capacity to migrate, adhere, and seal off the contaminated area, it is used during gastrointestinal surgeries, neurosurgeries, orthopedic surgeries, etc.
What Is Omental Torsion?
It is a condition where the omentum twists along its long axis to the extent that it loses its vascularity (blood supply). The twist is in a clockwise direction and is localized on the right side of the abdomen. The torsional force is enough to compromise (cut off) the venous return from the omentum, leaving only arterial flow; this will lead to excess blood flow with no way to return back.
This causes extravasation (leaking) of serosanguineous (blood mixed with serum) fluid into the peritoneal cavity causing sudden pain on the right side of the abdomen, often mimicking appendicitis, and it is associated with nausea, vomiting, and fever.
Why Does Omental Torsion Occur?
It is a cumulative effect of predisposing and precipitating factors. The predisposing factors are-
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Anatomic variations such as bifid (twisted) omentum, accessory (extra) omentum, and narrowed omentum pedicle (stalk).
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Obesity leads to an irregular accumulation of fat.
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Redundant venous veins twist around the shorter arteries.
The precipitating factors causing displacement of the omentum include-
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Trauma.
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Violent exercise.
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Hyperperistalsis (excessive involuntary constriction of the muscles in the small intestine).
There are two types of omental torsion - primary and secondary. Primary torsion is uncommon and occurs due to abnormal thickening of the ligaments in the omentum. Secondary torsion, on the other hand, is relatively common and often mistaken for appendicitis and is always caused due to an underlying pathology such as
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Cyst - Although rarely seen, omental cysts should be considered as a diagnosis hypothesis in children with abdominal pain.
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Tumor - Since the omentum has a rich supply of blood and lymph vessels, tumors can be derived from any of these structures.
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Intra-Abdominal Inflammation - Inflammation is an immune response to an underlying infection or abscess leading to the accumulation of fluid and excess pressure between the peritoneum and the omentum.
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Post-Surgical Wounds and Scarring - As a part of the repair process after abdominal surgery, the body replaces the damaged vascular soft tissue with thick collagen fibers, which predispose the omentum to torsion.
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Hernial Sacs - Seen in patients with an inguinal hernia; along with the small intestine, the omentum also gets strangled and infracted.
What Are the Investigations Done to Diagnose Omental Torsion?
Omental torsion is a surgical emergency; hence, extensive investigations are not recommended; however, the following tests are prerequisites for diagnosis-
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Computed Tomographic (CT) Scan - It is highly sensitive to omental masses and may show the characteristic twisted appearance of the twisted omentum.
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Magnetic Resonance Imaging (MRI) - It is effective in diagnosing complicated omental torsions associated with bleeding and abscesses.
Diagnosing omental torsion is extremely difficult because of the non-specific symptoms and insufficient evidence; an alternative strategy involves observing for abnormalities in the appendix, gallbladder, and pelvic cavity; if all of them are normal, it is likely that the symptoms are caused due to omental torsion. The presence of serosanguineous (serum mixed with blood) fluid is also characteristic of omental torsion.
How Is Omental Torsion Treated?
The first line of treatment is always conservative pharmacotherapy with analgesics, anti-inflammatories, and antibiotics; if the patient's conditions worsen, laparoscopic omentectomy is done to remove the affected portion of the omentum, along with the associated underlying causes for the torsion.
Laparoscopic Omentectomy -
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After anesthesia, the patient is placed in the supine position, and multiple small incisions are made over the abdomen. The abdominal cavity is accessed with the help of a trocar (a sharp surgical instrument with a cannula); consequently, four accessory trocars are placed in the right and left upper quadrant, lower left quadrant, and above the pubic bone.
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Abdominal exploration is done with a laparoscope introduced through the cannula of the trocar. In patients with omental torsion, the omentum will be hemorrhagic and ischemic and will be adhered to the right abdominal wall and transverse colon, but the appendix, gallbladder, and the transverse colon will appear normal.
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The procedure is continued by carefully resecting the adhesion between the omentum and the right abdominal wall and transverse colon. The twisted omentum is freed from all the adhesions, and the specimen is placed in a bag and removed through the small incision. The incisions are sutured, and the patient is under observation till their vitals are stable.
What Are the Complications of Omentectomy?
An omentectomy is a relatively safe procedure with minimal side effects; they are-
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Temporary pain or tenderness.
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Risk of bleeding, infection, and nerve damage.
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Fluid retention due to blocked lymphatic vessels.
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Small bowel obstruction is an exclusive complication of abdominal surgeries. The operated site, after healing, replaces the soft tissue with fibrous tissue, thereby reducing the lumen of the small intestine through which the food and liquids pass. This causes obstruction in the small intestine.
Irrespective of the complications, omentectomy is an emergency procedure and should be diagnosed and treated early to avoid life-threatening conditions.
What to Expect After Omectectomy?
The patient is given post-operative instruction on how to keep the incision sites clean and sent home after four to eight days. They are recalled for the post-operative follow-up to check for persisting symptoms and recurrence. Regeneration of the omentum after partial omentectomy is done by the underlying active omentum. The remaining healthy omentum releases angiogenic and growth factors to facilitate the growth of new blood and lymph vessels, assuring a fresh blood supply that salvages the tissue from ischemic damage.
Conclusion:
Omental torsion is a rare complication that can be treated successfully with laparoscopic omentectomy. The success of the procedure depends on the duration of the torsion because prolonged torsion increases inflammation which complicates the surgery. Omental torsion is one of those procedures that advocates early surgical intervention for better outcomes.
