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Epiploic appendagitis

Epiploic appendagitis is a rare self limiting inflammatory/ischaemic process involving an appendix epiploica of the colon, and may either be primary or secondary to adjacent pathology. This article pertains to primary (spontaneous) epiploic appendagitis

Epidemiology

This condition usually affects patients in their 2nd to 5th decades with a predilection for women and obese individuals, presumably due to larger appendices 6

Clinical presentation

Clinically patients present with abdominal pain and guarding. It is essentially indistinguishable from diverticulitis and acute appendicitis (depending on location) and although an uncommon condition, it accounts for up to 7% of cases of suspected diverticulitis 1. Since there is focal peritoneal irritation, pain maybe more localized than in the other causes of acute abdominal pain.

Pathology

Epiploic appendagitis merely denotes inflammation of the one or more appendices epiploicae, which number 50-100 and are distributed along the large bowel with variable frequency 3-4,6:

  • rectosigmoid junction - 57%
  • ileocecal region - 26%
  • ascending colon - 9%
  • transverse colon - 6%
  • descending colon - 2%

The pathogenesis is thought to be due to torsion of a large and pedunculated appendix epiploicae, or spontaneous thrombosis of the venous outflow, resulting in ischaemia and necrosis 3.

Radiographic features

Ultrasound

Ultrasound guided by the patients area of maximal tenderness may reveal a rounded, noncompressible, hyperechoic mass, without internal vascularity, and surrounded by a subtle hypoechoic line 5. They are typically 2-4 cm in maximal diameter.

They typically exert local mass effect but are not usually associated with bowel wall thickening or ascites 5.

CT

CT appearances are usually characteristic consisting of:

  • a fat-density ovoid structure adjacent to colon, usually 1.5- 3.5cm in diameter 2
  • thin high-density rim (1-3mm thick) 5-6
  • surrounding inflammatory fat stranding, and thickening of the adjacent peritoneum
  • central hyperdense dot (representing the thrombosed vascular pedicle) 6

Chronically, an infarcted appendix epiploica may calcify, and may detach to form an intraperitoneal loose body. 

It may rarely involve the vermiform appendix epiploic appendages as so called epiploic appendagitis of the vermiform appendix 8, mimicking appendicitis both clinically and potentially on CT.

MRI

Although not frequently performed for this indication MRI features are also characteristic 6:

  • T1 - often shows a rounded high signal mass with slightly reduced signal compared to normal fat, due to inflammatory stranding; hypointense 2-3 mm rim
  • T2 - often seen as a high signal mass which attenuates on fat suppressed sequences; hyper-intense 2-3 mm rim with surrounding high signal stranding; central low signal vein
  • T1 C+ (Gd) - shows vivid rim enhancement

Treatment and prognosis

Epiploic appendagitis is a self limiting disease, and thus correct identification on CT prevents unnecessary surgery 2. Although it sometimes mimics acute abdominal diseases for which surgery is required, treatment options for epiploic appendagitis often do not include surgery, 

Differential diagnosis

Imaging differential considerations include

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