Sclerosing Mesenteritis: "Fat Ring Sign".

A 72-year-old man with hypertension and benign prostatic hyperplasia presented to the gastroenterology department with a several-year history of abdominal discomfort. He was afebrile, and his abdomen was soft without tenderness. Laboratory testing showed a leukocyte count of 8,900 per microliter (reference range, 3,500 to 8,500) and a serum C-reactive protein level of 0.53 mg per deciliter (reference range, 0.0 to 0.3). Computed tomography (CT) revealed a mesenteric mass with high attenuation and hypoattenuated fat surrounding the mesenteric vessels (so-called “fat ring sign”) (Fig. 1). Esophagogastroduodenoscopy and colonoscopy showed no identifiable causes of inflammation. Malignancies, IgG4-related diseases, and infections were excluded by further examination. Sclerosing mesenteritis was diagnosed by the abovementioned findings. Conservative therapy was initiated; thus, he has had no exacerbation for more than two years.

FIG. 1

Plain and contrast-enhanced abdominal computed tomography (CT) revealing a mesenteric mass with high attenuation and hypoattenuated fat surrounding the mesenteric vessels, the so-called “fat ring sign” (arrowheads) (A: plain CT, B: contrast-enhanced CT).

Sclerosing mesenteritis is a rare benign disease characterized by chronic inflammation involving the mesentery.12 The etiology is unknown.12 Sclerosing mesenteritis may be asymptomatic and found incidentally on imaging, or associated with non-specific symptoms including abdominal pain, fever, nausea, vomiting, change in bowel habits.12 In addition, sclerosing mesenteritis can occasionally result from mass effect on gastrointestinal lumen, mesenteric vasculature, or lymphatics (e.g., bowel obstruction, ischemia, chylous ascites).1

The differential diagnosis of sclerosing mesenteritis includes any condition associated with mesenteric edema, hemorrhage, and infiltration with inflammatory or neoplastic cells such as trauma, ischemia, cancer, autoimmune diseases, and infections.1 CT is useful for the diagnosis of sclerosing mesenteritis; particularly, “fat ring sign” which refers to a preserving rim of fat around a mesenteric vessel is an important diagnostic finding.12 If the mesenteric lymph node is ≥10 mm, malignancy must be excluded through biopsy or positron-emission tomography-CT.1 There is extremely limited evidence for management of sclerosing mesenteritis.1 Observation is recommended for asymptomatic or mildly symptomatic patients.1