Omental Torsion

Practice Essentials

Omental torsion is a condition in which the organ twists on its long axis to such an extent that its vascularity is compromised. Although it is rarely diagnosed preoperatively, knowledge of this entity is important to the surgeon because it mimics the common causes of acute surgical abdomen. Eitel first described omental torsion in 1899; since then, only about 300 cases have been reported.^[1]

Omental torsion usually occurs in adults. The twisted portion of the omentum tends to be localized to a right-side segment, thereby giving rise to the sudden onset of pain and signs of peritoneal irritation on the right side of the abdomen. The condition may be associated with nausea, vomiting, or low-grade fever. An abdominal mass may be palpable.

Ultrasonography (US) and computed tomography (CT) may show a characteristic appearance of twisted omentum; however, because the disease may mimic other surgical emergencies, extensive radiologic studies are usually not indicated.

Treatment consists of resection of the affected portion of the omentum. Any disease process associated with secondary torsion should be corrected.

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Pathophysiology

In omental torsion, the omentum twists around a pivotal point, usually in a clockwise direction (see the image below). Venous return is compromised, and the distal omentum becomes congested and edematous. Resultant hemorrhagic extravasation creates a characteristic serosanguineous fluid in the peritoneal cavity.

View Image

Example of primary torsion of omentum. Normal-appearing omentum can be seen above torsion point. Omentum below that point is edematous and congested.

As the torsion progresses, arterial occlusion leads to acute hemorrhagic infarction, and eventual necrosis of the omentum occurs. Spontaneous derotation may be possible and may explain omental adhesions in the right lower quadrant, which are often found during laparotomy and have no clear cause.

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Etiology

Torsion of the omentum may be either primary or secondary. In primary torsion, a mobile segment of omentum rotates around a proximal fixed point in the absence of any associated intra-abdominal pathology. Although the precise cause is unknown, both predisposing and precipitating factors in the pathogenesis of the condition can be identified.^{[2, 3, 4, 5, 6]}

Factors that predispose a patient to torsion include anatomic variations of the omentum itself, such as accessory omentum, bifid omentum, irregular accumulations of omental fat (in patients who are obese), and narrowed omentum pedicle. Any redundancy of omental veins may lead to kinking and twisting around the shorter and tenser arteries. The higher incidence of torsion on the right side of the omentum is related to the greater size and mobility of that side.

Precipitating factors are those causing displacement of the omentum, including trauma, violent exercise, and hyperperistalsis with resultant increased passive movement of the omentum.

Secondary torsion is more common than primary torsion and is associated with preexisting abdominal pathology, including cysts, tumors,^[7] foci of intra-abdominal inflammation, postsurgical wounds or scarring, and hernial sacs. Most cases of secondary torsion occur in patients with inguinal hernias.^[8]

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History and Physical Examination

Torsion of the omentum is difficult to diagnose clinically in the preoperative setting. Accurate preoperative diagnosis was reported in the range of 0.6-4.8%. In a report from Greece, for example, a 14-year-old boy who was admitted to the hospital for acute appendicitis was found during surgery to be suffering from omental torsion on the long axis.^[9]

Omental torsion usually occurs in adults (of either sex). The twisted portion of the omentum tends to be localized to a right-side segment, thereby giving rise to the sudden onset of pain and signs of peritoneal irritation on the right side of the abdomen. The condition may be associated with nausea, vomiting, or low-grade fever. An abdominal mass may be palpable in half of the patients.

This right-side acute pain with rebound tenderness is often mistaken for acute appendicitis,^[10] acute cholecystitis, or twisted ovarian cysts. At laparotomy, the finding of free serosanguineous fluid in association with a normal appendix, gallbladder, or pelvic organs should alert the surgeon to the possibility of omental torsion.

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Laboratory Studies

A complete blood count (CBC) may reveal moderate leukocytosis, which occurs in two thirds of cases of omental torsion.

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Imaging Studies

Reports suggest that ultrasonography (US) and computed tomography (CT) may show a characteristic appearance of twisted omentum; however, because the disease may mimic other surgical emergencies, extensive radiologic studies are usually not indicated.

CT may show a concentric distribution of fibrous and fatty folds converging radially toward the torsion.^{[11, 12]} US, on the other hand, may show a complex mass and mixture of solid material and hypoechoic zones.

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Procedures

Laparoscopy is a safe diagnostic and therapeutic modality.^{[13, 14]} In a report from Italy, for example, US and radiologic findings in three patients who presented with acute abdominal symptoms were unclear, prompting the use of diagnostic laparoscopy.^[15] In another report, laparoscopic examination allowed exploration of the entire peritoneal cavity, thereby facilitating an accurate diagnosis of omental torsion, followed by laparoscopic resection of necrotic omentum, in each patient.^[16]

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Surgical Therapy

Preoperative differential diagnosis includes acute appendicitis, acute cholecystitis, and twisted ovarian cysts. Torsion of the omentum is usually discovered during laparotomy or laparoscopy for an acute abdomen.^[13]  With the advent of diagnostic laparoscopy and the increased demand for laparoscopic appendectomy, omental torsion may become a more frequently recognized clinical entity.

Omental torsion should be considered if preoperatively diagnosed acute appendicitis is not found and if the gallbladder and ovaries reveal no disease. In addition, the presence of serosanguineous fluid in the peritoneal cavity mandates inspection of the omentum to exclude torsion.

Treatment consists of resection of the affected portion of the omentum. Any disease process associated with secondary torsion should be corrected.^[17]

An incision centered over the site of maximal tenderness facilitates the operative diagnosis and eases resection of the infarcted omentum. When a healthy appendix is found, the cause of the abdominal pain should be sought.

First, the cecum should be inspected for a perforated diverticulum. The terminal ileum is then examined for Meckel diverticulum and regional enteritis, and the pelvic organs are inspected and palpated for disease.

The gallbladder and duodenum should be visualized, and the mesentery should be evaluated for mesenteric lymphadenitis. Exploration of the abdomen should continue until the cause of acute abdominal symptoms has been identified. This may require extension of the original incision or creation of a new incision.

Successful treatment via a laparoscopic approach has been reported.^{[18, 19]}

Postoperative recovery is usually rapid, and morbidity is minimal. If left untreated, the natural process of omental torsion is necrosis and fibrosis.

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