Epiploic appendagitis and omental infarction are benign self-limiting conditions that are more frequent than generally assumed. Both disorders fre-
quently mimic symptoms of an abdominal surgical emergency, often leading to clinical misdiagnosis of appendicitis. Discriminating between both conditions is of no practical relevance since treatment and prognosis are identical (van Breda Vriesman and Puylaert 2002). Spontaneous and complete resolution of symptoms, typically within 2 weeks, is the rule. Obesity seems to be an important risk factor for primary omental torsion in children. Varjavandi et al. (2003) postulated that the increased fat deposition in obese children outstrips the blood supply to the developing omentum. This could lead to either relative ischemia as the inciting event, increased omental weight leading to torsion, or traction to the most distal parts of the omentum. At gray-scale and color Doppler sonography, the more frequent appearance is a hyperechoic mass containing poorly defined nodular or linear hypoechoic areas with few vessels within the mass and hyperemia in the peripheral area. The hyperechoic area corresponds to preserved omental tissue with edema and vascular congestion, the avascular hypoechoic areas
Fig. 1.76a-c. Omental infarction. a Hyperechoic mass just behind the abdominal wall (arrows). b Axial CT image shows an area of fat stranding indicating inflamed mesenteric fat (arrows). c Another patient. Longitudinal US at the sub-hepatic region shows a hyperechoic mass just underneath the anterior abdominal wall that progressively attenuates the sound suggesting a fat origin (arrows). B,dilated bowel loops; L, liver corresponding to infarcted tissue (Baldisserotto et al. 2005). Sometimes a progressive sound attenuation is detected (Fig. 1.76). Small amounts of free intraabdominal fluid between bowel loops and in the cul-de-sac are routinely observed (Theriot et al. 2003). The lesion is more conspicuous on CT studies, appearing as a well-circumscribed region of inflamed omental mass interspersed with hyper-attenuating stripes and inflammatory stranding (Fig. 1.76). The underlying colon, terminal ileum, and appendix remain unaffected (Birnbaum and Jeffrey 1998).
Epiploic appendices are pedunculated adipose structures protruding from the serosal surface of the colon. An epiploic appendix might incidentally undergo infarction because of torsion or spontaneous venous thrombosis. The condition has been called epiploic appendagitis (van Breda VriesmaN and Puylaert 2002). It is considered, as with omental infarction, a self-limited process, and the appropriate management is conservative. The inflamed mass is often delineated by a hypoechoic ring on US.
The corresponding CT findings consist of a small pedunculated fat-attenuation mass with a hyperat-tenuating rim (BiRNbaum and JEffREy 1998).
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