Regarding six cases of mesenteric panniculitis: US, spiral CT, Magnetic Resonance.

PURPOSE: Mesenteric panniculitis is a rare inflammatory disease. The inflammation produces a lesion which appears as a mass, and normally produces abdominal pain without any other significant clinical signs. The radiological pattern is not typical, but the diagnosis is aided by a number of elements which are important to recognise in order to avoid invasive diagnostic methods or therapy. Six cases are presented, all evaluated with sonography, Color-Doppler US, Spiral CT and Magnetic Resonance Imaging (MRI).

MATERIALS AND METHODS: We evaluated six patients with negative clinical histories and endoscopic examinations. The patients reported the recent onset of indefinite symptoms and abdominal pain treated at home. Abdominal plain film radiography, performed also in the upright position, was negative in all cases. All the patients underwent abdominal sonography and Colour-Doppler ultrasound. Spiral CT scanning was carried out with 5-mm slice thickness, a pitch of 1.3, and single breath-hold volumetric acquisitions starting 60 s after intravenous injection of iodinated contrast medium. Only in one case, where Crohn's disease was suspected and subsequently not confirmed, did we perform small bowel enema with transparent contrast medium to distend the bowel loops. MR imaging was performed using a medium-field 0.5 T magnet, T1-weighted Fast SE, T2-weighted Fast SE and Fast STIR sequences. We considered: the mass effect of the lesion; the presence of vascular infiltration; the presence of a peripheral pseudocapsule; the presence of perivascular loose tissue proper, having densitometric characteristics distinctive from the remaining fatty tissue of the diseased mesentery.

RESULTS: In all cases ultrasound detected only an central abdominal mass. The fatty content of the mass, however, reduced US transmission, preventing the acquisition of more complete information. The color-Doppler US also produced little data, except some isolated colour spots within the mass. In no case did CT directly detect a peripheral pseudocapsule, although it did identify a difference in density between the perivisceral abdominal loose tissue and the mesentery proper, which is hyperdense. The vessels inside the mesentery on no occasion appeared infiltrated. The CT scans were unable to identify differential elements between the perivascular loose tissue and the fatty tissue of the main mass. MRI, on the other hand, enabled the detection of the peripheral pseudocapsule which surrounded the mesenteric mass as a band of tissue with low signal intensity in all the sequences performed. In fast STIR sequences suppression of the fat signal of the mesenteric mass was insufficient, being suppressed only in the adipose tissue surrounding the arterial branches of the mesenteric artery. Four of the six patients underwent exploratory laparotomy. The histological examination of the biopsies revealed a massive inflammatory infiltration of the mesentery, with relatively little involvement of the perivascular adipose tissue.

CONCLUSIONS: In mesenteric panniculitis, sonography and spiral-CT are useful in focusing diagnostic attention on the mesentery, but only MRI is capable of providing the information necessary formulating a complete diagnosis of the disease.