Imaging Pearls ❯ Small Bowel ❯ Omentum
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- Omental Infarction: Facts
- Omental infarction, with or without torsion, is a rare cause of acute abdominal pain, which makes it a difficult and unusual diagnosis to make. When compared with appendicitis, torsion has an incidence of 0.0016% to 0.37%, which is a ratio of less than 4 cases per 1000 cases of appendicitis.
- The primary symptom associated with omental torsion is pain, which is frequently localized in the right lower quadrant of the abdomen. The onset of pain is usually sudden and does not radiate to the abdominal wall . In many cases, the pain localizes in the right lower quadrant and reveals signs of peritoneal irritation. - “ Omental torsion can present in 2 ways. In primary torsion, anatomic malformations such as a bifid or accessory omentum cause a spontaneous torsion; sudden movements, violent exercise, and hyperperistalsis have been implicated as precipitating factors. Obesity is also a well-documented risk linked to primary torsion, with one study documenting that almost 70% of patients with omental infarction were obese. It is postulated that excess fat unevenly distributed in the omentum acts as a lead point for torsion. Secondary torsion occurs most often because of hernia, tumor, or adhesion, with the dependent omentum becoming fixed in the torsed position and unable to untwist. Both of these processes may lead to infarction of the affected omentum.
“Acute Abdomen due to Primary Omental Torsion and Infarction
S. Occhionorelli et al.
Case Reports in Surgery
Volume 2014, Article ID 208382 - “ Differential diagnosis should include appendicitis, cholecystitis, cecal diverticulitis, perforated duodenal ulcer, abdominal wall hematoma, and intestinal obstruction. In women of reproductive age, salpingitis, ovarian cyst torsion, and ectopic pregnancy should also be considered. In children, differential diagnosis should also include Meckel diverticulum and mesenteric adenitis. Finally, torsion of accessory spleen is another diagnostic possibility, due to the fact that accessory spleen, when it exists, usually resides inside the omentum.”
Acute Abdomen due to Primary Omental Torsion and Infarction
S. Occhionorelli et al.
Case Reports in Surgery
Volume 2014, Article ID 208382 - “Specific CT findings in omental torsion include diffuse streaking in a whirling pattern of fibrous and fatty folds . A basic advantage of CT versus a US scan is the reliability of identifying the mass in the characteristic location between the anterior abdominal wall and the colon.”
Acute Abdomen due to Primary Omental Torsion and Infarction
S. Occhionorelli et al.
Case Reports in Surgery
Volume 2014, Article ID 208382 - “ Intraabdominal fat is a metabolically active tissue that may undergo necrosis through a number of mechanisms. Fat necrosis is a common finding at abdominal cross-sectional imaging, and it may cause abdominal pain, mimic findings of acute abdomen, or be asymptomatic and accompany other pathophysiologic processes. Common processes that are present in fat necrosis include torsion of an epiploic appendage, infarction of the greater omentum, and fat necrosis related to trauma or pancreatitis.”
Imaging manifestations of abdominal fat necrosis and its mimics.
Kamaya A, Federle MP, Desser TS
.Radiographics. 2011 Nov-Dec;31(7):2021-34
- Omental Infarction: Facts
- Right sided
- Cause: congenitally fragile blood supply to omentum
- susceptible to infarction
- Self-limited
- Conservative treatment usually is satisfactory - Omental Infarction: Facts
- Rare cause of an acute abdomen with an equivalent of less than four cases per 1000 cases of appendicitis
- Can be misdiagnosed as appendicitis, peptic ulcer disease, cholecystitis, pancreatitis
- Right half of omentum is more commonly involved than the left side of the omentum - Secondary Omental Infarction: Facts
- Usually near site of prior surgery or inflammation
- Can be confused with a range of pathologies including appendix epiploicae
- Either primary or secondary omental infarction can result from omental torsion or vascular occlusion - “The diagnosis of omental infarction is based primarily on CT findings of a triangular or oval heterogeneous fatty mass that is located between the anterior abdominal wall and the transverse or ascending colon fat density [9]. Omental torsion as a cause of omental infarction is suggested at CT when a whirled pattern of concentric linear strands is seen. Distinction from diverticulitis can be made by lack of an adjacent diverticulum, abscess, and bowel wall thickening.”
Omental Infarct: CT imaging Features
Singh AK et al.
Abdom Imaging (2006) 31:549-554 - “Unlike acute appendagitis, in which CT changes re- solve completely, 6 months after the acute presentation omental infarcts in our series had shrunk but did not resolve in any patient. In general, the heterogeneous fatty lesion in the omentum shrank and developed a well-de- fined hyperdense rim on follow-up CT scan.”
Omental Infarct: CT imaging Features
Singh AK et al.
Abdom Imaging (2006) 31:549-554