Omental infarction is a rare cause of acute abdomen resulting from vascular compromise of the greater omentum. This condition has a non-specific clinical presentation and is usually managed conservatively.
Along with epiploic appendagitis and perigastric appendagitis, the term omental infarction is grouped under the broader umbrella of intraperitoneal focal fat infarction 9.
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Clinical presentation
Patients may present with 1:
sudden onset of abdominal pain
right lower quadrant pain and tenderness
absence of fever and gastrointestinal symptoms
encountered in healthy patients, such as marathoners, because of low omental blood flow
Pathology
Primary omental infarction
The classic location of primary omental infarction is in the right lower quadrant medial to the ascending colon or cecum. The vascular compromise occurs along the right edge of the greater omentum where the arterial supply is usually tenuous.
Sometimes it is the result of kinking of venous channels in the inferior part of the greater omentum in the pelvis. Occasionally omentum twists on itself resulting in omental torsion leading to both arterial and venous compromise. The omentum may infarct without torsion, and this is called primary idiopathic segmental infarction 8.
Secondary omental infarction
post-surgery
abdominal trauma
omental inflammation
Radiographic features
Primary omental infarction is usually seen in the right lower quadrant. Secondary omental infarction is located at the site of initial insult. It is usually larger than 5 cm, which helps distinguish it from epiploic appendagitis 1.
Ultrasound
focal area of increased echogenicity in the omental fat
CT
focal area of fat stranding
swirling of omental vessels in omental torsion
hyperdense peripheral halo
encapsulated fatty lesion 10
Treatment and prognosis
This condition is often self-limiting and can be managed conservatively. Occasionally complications such as abscess formation occur which require surgery or radiological drainage.
Differential diagnosis
General imaging differential considerations include:
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usually smaller areas of fat stranding compared to the omental infarction
ovoid central area of preserved fat
hyperdense central dot (thrombosed vessel)
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more a clinical differential, as the appendix should be identified inflamed
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fat stranding surrounding a colonic diverticulum
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when differentiating from the omentum, remember that the mesentery always has a bowel loop at its end
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liposarcoma
peritoneal liposarcoma may resemble encapsulated omental infarction; thick enhancing septa are in favor of a liposarcoma 10