M-mode ultrasound for assessment of the "tethered fat sign" in children: an easily performed way to certify a dynamic process as a still picture.

ABSTRACT

Background: Omental infarction is a rare pediatric disease. Ultrasound is a useful modality for a non-invasive pre-operative differential diagnosis between inflammatory conditions (as appendicitis) and omental infarction, especially by detecting immobility of the omentum adhered to the abdominal wall ("tetherd fat sign"). However, this is a dynamic sign that cannot be documented in a static image with B-mode technique. The goal of this work is to incorporate the versatile function of motion mode (M-mode) into omental infarction diagnosis to describe how the M-mode is useful in the evaluation of fat motion in children suspected of having omental infarction. In 2019 we suggested a new Ultrasound sign named "tethered fat sign" for an accurate non-invasive diagnosis of omental infarction in children. This finding was observed in 6 of the 234 seen children of our previous study with 4 laparoscopic confirmed diagnosis. Methods: From January 2019 to July 2021, we evaluated 195 children (91 boys and 104 girls, from 3 to 15 years) admitted to our Santobono-Pausilipon Children Hospital with acute right-sided abdominal pain. Abdominal ultrasound was performed to all the patients and the investigation of "tethered fat sign" was always included. Results: In 7 patients ultrasound showed the presence of a hyperechoic oval mass localized in the right upper abdominal quadrant and in 2 of these M-mode documented a normal subhepatic fat moving during respiratory movements in relation with the abdominal wall. The remaining 5 patients had an omental infarction showed as a subhepatic motionless mass tethered to the abdominal wall on M-mode. In these patients, a sonographic follow-up was performed every 15 d for 2 months showing a progressive reduction in size of the right-sided hyperechoic mass. Conclusions: In the evaluation of all children who showed the presence of the "tethered fat sign" the use of M-mode provide a certified image in diagnostic ultrasound.