Mesenteric panniculitis. Part 1: MDCT--pictorial review.

Mesenteric panniculitis is an uncommon benign inflammatory condition of unknown etiology that involves the adipose tissue of the mesentery and for which an extremely varied terminology has been used, causing considerable confusion. It can be evaluated as a single disease with two pathological subgroups: Mesenteric Panniculitis (MP), representing the very large major subgroup where inflammation and fat necrosis predominate and Retractile Mesenteritis (RM), much rarely found, where fibrosis and retraction predominate. In histo-pathological terms the preferred terminology is sclerosing mesenteritis. We hereby extensively illustrate the characteristic MDCT findings of MP through pictures selected among a collection of cases constituted over a 5-year period. All patients were scanned with 64-row MDCT equipment. We also review the literature and discuss the differential diagnosis. The radiological diagnosis of MP was based on classical CT signs described in the literature and comprising: the presence of a well-defined "mass effect" on neighbouring structures (sign 1) constituted by mesenteric fat tissue of inhomogeneous higher attenuation than adjacent retroperitoneal or mesocolonic fat (sign 2) and containing small soft tissue nodes (sign 3). It may typically be surrounded by a hypoattenuated fatty "halo sign" (sign 4) and an hyperattenuating pseudocapsule may also surround the all entity (sign 5). The last two signs are considered inconstant but very specific. The absence of histological verification constitutes the weakness of our study. The differential diagnosis of MP is extensive and includes all disorders that can affect the mesentery. The most common ones are lymphoma, well-differentiated liposarcoma, peritoneal carcinomatosis, carcinoid tumor, retroperitoneal fibrosis, lipoma, mesenteric desmoid tumor, mesenteric inflammatory pseudotumor, mesenteric fibromatosis and mesenteric edema. PET/CT is proved useful to correctly exclude mesenteric tumoral involvement in patients presenting with typical MR The course of MP is favorable in most cases and progression of MP to retractile mesenteritis not only appears very being rare but finally remains doubtful.