"Tethered Fat Sign": The Sonographic Sign of Omental Infarction

Our purpose is to describe the ultrasound sign for a correct non-invasive diagnosis of omental infarction in children. From January 2014 to December 2018, a total of 234 children (109 boys and 125 girls, age range 3-15 y) with acute right-sided abdominal pain, admitted to our hospital with a presumptive diagnosis of acute appendicitis, were prospectively evaluated. In all patients, abdominal ultrasound was performed, and the omental fat was always evaluated. In 228 patients, the omental fat resulted to be normal or hyperechogenic, never tethered, and they results affected by other causes of abdominal pain different from omental infarction (such as appendicitis, pancreatitis, urolithiasis and others). In the remaining 6 children, we found a hyperechoic mass between the anterior abdominal wall and the ascending or transverse colon in the right abdomen quadrant, suggesting the diagnosis of omental infarction. This subhepatic mass was always tethered to the abdominal wall, motionless during respiratory excursions. We named this finding the "tethered fat sign." The diagnosis was confirmed with laparoscopy in 4 children. The other 2 children were treated with conservative therapy. In these 2 patients, a sonographic follow-up was performed, showing a progressive reduction in size of the right-sided hyperechoic mass. In conclusion, our study suggests that the presence of the "tethered fat sign" may be an accurate sonographic sign for non-invasive diagnosis of omental infarction in children.