Imaging Manifestations of Abdominal Fat Necrosis and Its Mimics

Abstract

Intraabdominal fat is a metabolically active tissue that may undergo necrosis through a number of mechanisms. Fat necrosis is a common finding at abdominal cross-sectional imaging, and it may cause abdominal pain, mimic findings of acute abdomen, or be asymptomatic and accompany other pathophysiologic processes. Common processes that are present in fat necrosis include torsion of an epiploic appendage, infarction of the greater omentum, and fat necrosis related to trauma or pancreatitis. In addition, other pathologic processes that involve fat may be visualized at computed tomography, including focal lipohypertrophy, pathologic fat paucity (lipodystrophies), and malignancies such as liposarcoma, which may mimic benign causes of fat stranding. Because fat necrosis and malignant processes such as liposarcoma and peritoneal carcinomatosis may mimic one another, knowledge of a patient's clinical history and prior imaging studies is essential for accurate diagnosis.

Evaluating the Patient with Right Lower Quadrant Pain

“…56 Presence of a whirled pattern of concentric vessels and/or stranding can be associated with omental torsion. 56,59 Unlike epiploic appendagitis, omental infarcts are not surrounded by a continuous hyperattenuating rim abutting the adjacent colon and do not contain a focus of central high attenuation (Fig. 15).…”

“…PET/CT shows mild uptake of fluorine 18 ( 18 F) fluorodeoxyglucose (FDG) corresponding to the encapsulated fat-attenuation mass. 59 Omental infarction may be managed conservatively with oral analgesics, nonsteroidal anti-inflammatory drugs, and/or prophylactic antibiotics. 60 However, if conservative management fails because of intractable pain, peritoneal signs, or complication, such as abscess or bowel obstruction due to persistence of infarct omental tissue, laparoscopy may be performed to provide prompt symptomatic relief.…”

Seeing past the appendix: the role of ultrasound in right iliac fossa pain

“…The adjacent bowel is usually spared, although rarely a degree of wall thickening may be seen. 16 A definitive diagnosis is difficult to make on clinical findings and ultrasound imaging alone, and further crosssectional imaging is usually required. Management is usually conservative, although it is important to be aware of potential complications such as abscess formation.…”

Beyond appendicitis

“…By CT scan, torsed epiploic fat appears as an ovoid, fat-density area anterior or anterolateral to the colon, with adjacent peritoneal enhancement; with omental torsion, swirling blood vessels within fat anterior to the bowel are visible. On ultrasound, both appear echogenic at the location of maximal tenderness [70]. In several retrospective series, omental infarction occurred in school-aged, overweight, predominantly male children; diagnosis was generally established by CT scan, and ultrasound had low to moderate sensitivity [71][72][73].…”