Clinical History
A 75-year-old woman with anorexia and non-specific diffuse abdominal pain in the last month, with almost complete spontaneous resolution. Clinical examination and extensive blood analyses showed no relevant findings.
Imaging Findings
Post contrast CT images of the abdomen and pelvis, in the portal phase of enhancement, were obtained. An 8.7 x 6.4 cm mesenteric soft-tissue mass was detected, located in the small bowel mesentery, approximately in mid-line, extending inferior to the right hemiabdomen. The lesion trapped mesenteric vessels, with mild vascular engorgement but with no significant reduction of calibre (Figures 1 and 2). We did not detect presence of pathological mesenteric or retro-peritoneal lymph nodes, making the diagnosis of lymphoproliferative disorder unlikely.
Since the patient was almost asymptomatic and there was no significant vascular compromise, no treatment was administrated. Follow-up CT examination after 9 months showed spontaneous size reduction of the mesenteric mass (Figures 3 and 4).
Discussion
The term sclerosing mesenteritis refers to a spectrum of rare conditions of unknown cause characterized by chronic inflammatory changes affecting the mesentery. Sclerosing mesenteritis is considered a single disease divided into three variants on the basis of the tissue predominance in the mass: mesenteric panniculitis when chronic inflammation predominates, mesenteric lipodystrophy characterized mainly by fat necrosis and retractile mesenteritis when there is a preponderance of fibrosis [1, 2]. In most patients, the condition consists of a mixture of the three phenomena (inflammation, necrosis and fibrosis). However, in some patients, the mass will demonstrate sufficient preponderance of one tissue type to allow its categorization into one distinct histologic sub-type [1].
The CT appearance of sclerosing mesenteritis can vary from subtle increased attenuation in the mesentery to a solid soft-tissue mass [1, 3]. While the mass is typically ill-defined, heterogeneous and of relatively reduced attenuation in mesenteric panniculitis, it is usually denser, more homogeneous and better-defined in retractile mesenteritis [2]. The disorder mainly involves the mesentery of the small bowel, but can occasionally involve the mesocolon. It rarely involves the peripancreatic region, omentum, retro-peritoneum or pelvis [1, 4]. Partial intestinal luminal narrowing is a common finding in retractile mesenteritis, but complete stenosis is infrequent [4, 5]. Enlarged mesenteric or retro-peritoneal lymph nodes may also be described [1]. The ‘misty mesentery sign’ refers to the presence of subtle increased attenuation in the mesentery at CT, often associated with small to borderline-sized nodes [2].
One distinguishing feature of this process is the presence of a peripheral band of soft-tissue attenuation that limits the normal mesentery from the inflammatory process, which has been called tumoral pseudo-capsule and seems to appear in up to 50% of patients [2, 4]. The mass may also involve the mesenteric vessels and collateral circulation may be found as a result. The presence of a halo of fat around the involved vessels, which is called ‘fat ring sign’, has been described in sclerosing mesenteritis and it is a valuable clue to distinguish this disease from other infiltrating processes such as lymphoma, carcinoid tumour or carcinomatosis [1, 4, 5]. Calcifications in the central necrotic area and cystic components may also be found [1, 5].
The prognosis of the disease is variable and three modes of progression have been described: partial or complete resolution of the inflammatory process, a non-progressive course and an aggressive course that occasionally has a fatal outcome [4]. However, most patients has a favourable prognosis [4, 5].
Differential Diagnosis List
Sclerosing mesenteritis with fibrosis preponderance (retractile mesenteritis)
Lymphoma
Desmoid tumour
Carcinoid tumour
Inflammatory pseudotumour
Primary mesenteric mesothelioma
Carcinomatosis
Final Diagnosis
Sclerosing mesenteritis with fibrosis preponderance (retractile mesenteritis)
