Diagnostic Ultrasound - Abdomen and Pelvis

Epiploic Appendagitis
TERMINOLOGY
Abbreviations
• Epiploic appendagitis (EA)
Synonyms
• Appendicitis epiploicae
Definitions
• Primary EA refers to ischemic infarction of epiploic
appendage secondary to either torsion or spontaneous
central draining vein thrombosis
• Secondary EA is caused by inflammation of adjacent
structure
IMAGING
General Features
• Best diagnostic clue
○ Fat-containing ovoid structure with surrounding
mesenteric fat stranding adjacent to colonic wall
• Location
○ Rectosigmoid junction (57%)
○ Ileocecal region (26%)
○ Ascending colon (9%)
○ Transverse colon (6%)
○ Descending colon (2%)
• Morphology
○ Epiploic appendages are small (0.5-5 cm long and 1-2 cm
thick), fat-containing, peritoneal outpouchings arising
from antimesenteric serosal colonic surface
○ In acute EA, appendage becomes swollen with mean
diameter of 1.5-3.5 cm
Ultrasonographic Findings
• Grayscale ultrasound
○ Noncompressible hyperechoic oval mass adjacent to
colon
○ Hypoechoic rim of inflamed visceral peritoneum (93%)
deep to region of maximal tenderness
○ May contain central hypoechoic areas of hemorrhagic
change
○ Adjacent absent or minimal bowel wall thickening with
local mass effect
• Color Doppler
○ Absence of central blood flow (useful differentiating
feature from secondary epiploic appendagitis)
• Contrast-enhanced ultrasound
○ Rim of peripheral arterial hyperenhancement
○ Central nonenhancing hypoechoic regions
CT Findings
• CECT
○ Ovoid pericolonic fat-density lesion measuring < 5 cm
abutting antimesenteric colonic wall
○ Localized mass effect on adjacent bowel wall
○ Central dot sign: Central hyperattenuating focus
representing central engorged or thrombosed vessel
&/or central areas of hemorrhage
○ Hyperattenuating ring sign: 2-3 mm hyperdense rim
surrounding ovoid lesion representing inflamed visceral
peritoneum
○ Surrounding inflammatory changes: Fat stranding,
parietal peritoneal thickening, and mild localized
asymmetric adjacent colonic wall thickening
Imaging Recommendations
• Best imaging tool
○ When clinically suspected, focused high-resolution
ultrasound is preferred, especially in younger age group
– Often CT is performed in acute setting, if diagnosis is
clinically unsuspected
○ CT is performed for patients with inconclusive US
findings
○ CT aids differentiation from alternative pathology and
aids identification of secondary complications
• Protocol advice
○ Focused high-resolution ultrasound examination at point
of maximum tenderness: Searching for noncompressible
avascular hyperechoic oval mass with hypoechoic rim
○ Standard portal venous phase CECT
DIFFERENTIAL DIAGNOSIS
Segmental Omental Infarction
• Localized greater omental infarction secondary to torsion,
trauma, or central venous occlusion
• Lesion is centered within omentum and predominantly
occurs in right upper quadrant
• Focal lesion is larger (mean diameter: 7 cm)
• Absence of hyperattenuating ring sign
• Central dot sign may be present
• Can occur in pediatric population (15%)
Appendicitis
• Identification of abnormally noncompressible, inflamed
appendix with thickened enhancing wall
• ± calcified appendicolith
• Pericecal inflammation
• Increased color Doppler flow
Diverticulitis
• Secondary inflammation of epiploic appendages may be
seen
• Longer segment of colonic wall thickening
• Abscess formation more common
• May lead to colonic obstruction
• Tends to affect older patients (> 50 years)
• More likely to have elevated WBC count
Sclerosing Mesenteritis
• Distortion and thickening of small bowel mesenteric root
• Does not abut colonic wall
• Fat ring sign: Traversing mesenteric vessels have
surrounding spared fat halo
• Punctate calcification (rare) and small volume (usually < 5
mm) adjacent lymph nodes
Primary Tumors and Mesocolon Metastases
• Multiplicity and ill-defined margins
○ Lesions tend to be hypoechoic
• Centered on omentum and may be adherent to ventral
surface of colon
• History of primary neoplasm and absence of acute
abdominal pain at presentation
Diagnoses: Bowel
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