Purpose or Case Report: Omental infarction and epiploic appendagitis are subtypes of a broader entity of abdominal fat necrosis known as intraperitoneal focal fat infarction (IFFI). IFFI is an uncommon cause of acute abdominal pain in children, and a known mimicker of acute appendicitis. The CT appearance of IFFI is well described, but the appearance is less familiar on MRI and is a potential imaging pitfall. Familiarity with the MRI appearance of IFFI is particularly timely, given the growing use of MRI in the evaluation of right lower quadrant pain in children. The purpose of this educational exhibit is to review the clinical history, pathologic appearance and treatment of IFFI, and describe MRI features that will allow the radiologist to make the correct diagnosis.
Methods & Materials: A retrospective case review was performed of the local PACS and electronic medical record at our institution on all MR examinations performed for appendicitis from December 2016 to October 2017. Available clinical history, laboratory results, imaging, pathology and follow-up were reviewed
Results: One hundred one appendicitis protocol MRIs were performed between December 2016 and October 2017. Of those, four patients were diagnosed with omental infarction or epiploic appendagitis based on surgical pathology or clinical features, which represented 4% of the cases clinically suspected to be acute appendicitis. Of these four cases ultimately diagnosed as IFFI, one MRI was initially interpreted as possible appendicitis, and one as Meckel’s diverticulitis versus omental infarct. The third and fourth cases were diagnosed as omental infarction and epiploic appendagitis by MRI, with concordant clinical course and follow-up.
The four cases share the following common MRI features: localized T2 hyperintense inflammatory changes within the right lower hemiabdomen, interposed between the ascending colon and anterior abdominal wall; mild diffuse signal loss within the circumscribed changes from fat suppression on T2FS sequence compared to T2 sequence; noninflamed appendix identified distant from or near the inflammatory changes. Peripheral clefts of fluid around the localized inflammatory changes were noted in several cases.
Conclusions: IFFI is an uncommon cause of acute abdominal pain in children, and can clinically mimic acute appendicitis. Characteristic MR features described in this educational exhibit will aid the radiologist in making the correct diagnosis, leading to proper management and avoidance of unnecessary surgery