Diagnosis of omental infarction using Computed Tomography

Clinical History

A 61-year-old white male patient presented with a three-day history of increasing pain in his right upper abdomen. Prior to onset of these complaints, patient reported lifting multiple heavy objects during a move. At the time of presentation, the pain was not dependent on movement and was present at rest.

Imaging Findings

Computed Tomography (CT) revealed in the venous phase a hypodense (fat-equivalent attenuation) mass measuring about 7.3 × 6.4 × 4.4 cm caudal to the hepatic flexure of the colon. The mass displaced the colon and small bowel loops. On sagittal projection, the presence of a “whirl sign” was observed. In addition, there was non-specific intra-abdominal lymph node enlargement (up to 5 mm) and a moderate amount of ascites in the lower abdomen. Coincidental findings included multiple small hamartomas of the liver.

Discussion

The first report of omental torsion with secondary compromise of circulation was published by Oberst in 1882 [1].
Infarctions of the greater omentum are either primary or secondary, although the differentiation in the literature is not always uniform. Primary infarctions involve segmental necrosis secondary to omental torsion in the absence of other disorders. Secondary infarctions occur in the context of other disorders, most commonly in the post-operative period with omental rotation secondary to adhesions, and in peritoneal carcinosis. Infarctions secondary to venous thromboses are also assigned to the secondary group.
Primary torsion is a result of rotation of a part of the omentum along a longitudinal axis from some fixed point. Predisposing factors include anomalies of the omental contour (narrow base, division, inhomogeneous fat distribution), irregular omental vessels, mechanical alteration (blunt trauma to the abdomen), coughing and physical overexertion. Because of the larger proportion of the omentum that lies in the right half of the abdomen and the associated increased mobility, primary torsions occur predominantly on that side. Torsions are usually in a clockwise direction resulting in compromise of the veins draining the omentum. The subsequent congestion and oedema is followed by ischaemia and necrosis. Complications include extravasation of sanguinous ascites and aseptic peritonitis.
Secondary torsion is the result of rotation of a part of the omentum between its base and a second fixed point. Most commonly responsible are pre-existing pathological changes such as tumours, cysts, inflammatory changes, scar tissue and external hernias.
The present case most likely involves primary torsion of the omentum: onset of symptoms occurred in relation to an identified period of significant physical exertion in the absence of relevant pre-existing disorders.
The clinical picture was dominated by signs of local peritonitis or acute abdomen. Diagnosis should ideally be made on the basis on non-invasive examinations, especially in high-risk patients with significant concomitant disease. Here, abdominal CT plays an important role in visualising the characteristic signs of omental torsion. In addition, CT can identify a primary tumour or secondary masses in the omentum.
With respect to therapy options in cases of acute omental torsion, some authors prefer a laparoscopic approach with omental resection and the opportunity for expanded, direct diagnostics [2]. By contrast, other authors recommend a conservative approach as was used in the present case [3]. This is especially advisable in children in whom the probability of primary omental torsion is disproportionately higher than that of secondary omental torsion.

Differential Diagnosis List

Final Diagnosis

Omental infarction

URL:	https://eurorad.org/case/10694
DOI:	10.1594/EURORAD/CASE.10694
ISSN:	1563-4086