Omental Infarction

Omental infarction (OI) is a condition where the greater omentum is subjected to ischemic damage due to interrupted blood flow. It is rare and often characterized by right lower quadrant abdominal pain [1]. One in one thousand laparotomies performed is secondary to acute abdomen arising from OI.

OI can be classified into primary and secondary [2]. In primary disease, the exact pathogenesis is unknown. There is a greater incidence of OI on the right hand side, and literature suggests that the reason lies in abnormal vasculature, stemming from embryonic factors, making it particularly vulnerable to congestion and decreased blood flow [3]. This is often referred to as primary idiopathic segmental OI [4]. In some cases the omentum first twists around itself, which then leads to OI. Conditions that predispose to omental torsion are obesity, adhesions, increased peristalsis, intra abdominal masses, and increased abdominal pressure [5]. Obesity is thought to increase the risk of torsion because of the additional fat tissue that disrupts the arterial blood supply and increases the weight of the omentum [6]. Males are more affected by idiopathic OI than females. OI has been known to occur in children as well, notably those who are obese. Secondary OI results from various medical conditions such as trauma, surgery, vascular disease and hypercoagulable states.

Because of its uncommon occurrence and non specific presentation, OI is frequently misdiagnosed, as clinicians suspect more common causes of acute abdomen, namely appendicitis, acute cholecystitis, peptic ulcer disease and so on [7]. Constitutional symptoms such as fever, as well as gastrointestinal upset (nausea, vomiting, diarrhea) are usually absent. Right sided guarding may be elicited [3].

As the clinical picture is unreliable in diagnosis, more emphasis has been placed on imaging modalities. Because of their improved availability, accuracy, and thus detection rate, fewer exploratory laparotomies are being done [2] [8]. Furthermore, this may explain the apparent increased incidence of omental infarction, added to more awareness of the condition by physicians [9]. Radiology is thus paramount, as it confirms the diagnosis and influences management.

In primary omental OI, abnormalities are likely to be present in the right lower quadrant, whereas secondary OI mostly appears at the site of the causative injury. The distinction between idiopathic omental infarction, and infarction secondary to torsion can only be definitively made intra-operatively.

Imaging:

• Abdominal ultrasound: This may show a focused hyper-echoic accumulation of fat that is not compressible.
• Computerized tomography (CT): This may show a well demarcated lesion with fat stranding, between the anterior abdominal wall and the bowel [10]. Omental torsion may be indicated by twisted blood vessels, which is known as the swirl sign [8]. The whole lesion may have a hyperdense rim around it. Pelvic and abdominal CT scanning is the imaging modality of choice [11].

1. Kamaya A, Federle MP, Desser TS. Imaging manifestations of abdominal fat necrosis and its mimics. Radiographics. 2011;31(7):2021-2034.
2. Itenberg E, Mariadason J, Khersonsky J, Wallack M. Modern management of omental torsion and omental infarction: a surgeon's perspective. J Surg Educ. 2010;67(1):44-47.
3. Battaglia L, Belli F, Vannelli A, et al. Simultaneous idiopathic segmental infarction of the great omentum and acute appendicitis: a rare association. World J Emerg Surg. 2008;3:30.
4. Al-Jaberi TM, Gharaibeh KI, Yaghan RJ. Torsion of abdominal appendages presenting with acute abdominal pain. Ann Saudi Med. 2007;20(3-4):211-213.
5. Goti F, Hollmann R, Stieger R, Lange J. Idiopathic segmental infarction of the greater omentum successfully treated by laparoscopy: report of case. Surg Today. 2000;30(5):451-453.
6. Fragoso AC, Pereira JM, Estevão-Costa J. Nonoperative management of omental infarction: a case report in a child. J Pediatr Surg. 2006;41(10):1777–1779.
7. Danikas D, Theodorou S, Espinel J, Schneider C. Laparoscopic treatment of two patients with omental infarction mimicking acute appendicitis. JSLS. 2001;5(1):73–75.
8. Yoo E, Kim JH, Kim MJ, Yu JS, Chung JJ, Yoo HS, Kim KW. Greater and lesser omenta: normal anatomy and pathologic processes. Radiographics. 2007;27(3):707-720.
9. van Breda Vriesman AC, Puylaert JB. Epiploic appendagitis and omental infarction: pitfalls and look-alikes. Abdom Imaging. 2002;27(1):20-28.
10. Singh AK, Gervais DA, Lee P, Westra S, Hahn PF, Novelline RA, Mueller PR. Omental infarct: CT imaging features. Abdom Imaging. 2006;31(5):549-554.
11. Naffaa LN, Shabb NS, Haddad MC. CT findings of omental torsion and infarction: case report and review of the literature. Clin Imaging. 2003;27(2):116-118.