Sclerosing Mesenteritis

Published on 19/07/2015 by admin

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Last modified 19/07/2015

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 Misty mesentery: Increased attenuation of mesentery with fat stranding and induration

image Thin (usually < 3 mm) pseudocapsule encasing inflamed mesentery (tumoral pseudocapsule sign)
image Cluster of mildly enlarged mesenteric nodes
image Usually located in left upper quadrant mesentery
image Mesenteric vessels and nodes have halo of spared fat (fat ring or fat halo sign)
• Chronic phase

image Chronic fibrosis results in discrete fibrotic soft tissue mass with desmoplastic reaction
image “Stellate” appearance with calcification within mass
image Encasement of mesenteric vessels (especially portomesenteric veins) with resultant collaterals

– Small bowel wall edema and mucosal hyperemia as result of lymphatic/venous obstruction and ischemia
image Tethering of bowel loops can lead to bowel obstruction

TOP DIFFERENTIAL DIAGNOSES

• Retroperitoneal and mesenteric lymphoma
• Carcinoid tumor
• Mesenteric edema
• Desmoid tumor (fibromatosis)
• Carcinomatosis (mesenteric metastases)
• Primary visceral malignancy
• Inflammatory pseudotumor

PATHOLOGY

• Unknown etiology, but associations with prior surgery, trauma, infection, autoimmune diseases, and malignancies
• Classified histologically into 3 types or stages based on predominant tissue type in mass

image Mesenteric lipodystrophy: Fat necrosis > inflammation or fibrosis
image Mesenteric panniculitis: Acute inflammation ± fat necrosis > fibrosis
image Retractile mesenteritis: Fibrosis/retraction > inflammation or fat necrosis

CLINICAL ISSUES

• Acute mesenteritis can be cause of acute abdominal pain
• Natural history or frequency of progression to chronic fibrotic phase not well understood

image Most patients have stable or slowly progressing disease without symptoms
• Common complications in chronic phase include bowel obstruction, urinary tract obstruction, and bowel ischemia
• Treatment: Immunosuppressive therapy should be attempted initially

image Limited role for surgery, as surgical excision is very difficult in advanced cases due to vascular involvement
image
(Left) Initial CECT evaluation in an elderly man with abdominal pain shows infiltration of the jejunal mesentery marked by a pseudocapsule image.

image
(Right) Axial CECT in the same patient shows clusters of mildly enlarged mesenteric nodes image. No diagnosis was made at this time, and the patient was not given treatment.
image
(Left) The same patient returned for evaluation 5 years later, having had chronic pain intermittently for the entire time without a diagnosis being made. Axial CECT shows a soft tissue mass image in the mesentery that encases and narrows the mesenteric vessels.

image
(Right) Axial CECT in a 2nd study of the same patient shows a focus of calcification image within the fibrotic mesenteric mass. The infiltrated mesentery and pseudocapsule image are still evident. This case illustrates progression of the disease over time.

TERMINOLOGY

Synonyms

• Retractile mesenteritis, fibrosing mesenteritis, mesenteric panniculitis, mesenteric lipodystrophy, liposclerotic mesenteritis, systemic nodular panniculitis, xanthogranulomatous mesenteritis

Definitions

• Idiopathic inflammatory and fibrotic disorder affecting mesentery of unknown etiology

IMAGING

General Features

• Best diagnostic clue

image “Misty mesentery” with surrounding pseudocapsule, clustered prominent mesenteric lymph nodes, and halo of spared fat surrounding nodes and vessels
• Location

image Most common site: Root of jejunal mesentery

– 90% involve small bowel mesentery and primarily to left of midline (jejunal mesentery)
image Occasionally: Colon (transverse or rectosigmoid)
image Rarely: Peripancreatic, omentum, and retroperitoneum
• Morphology

image Mostly characterized by mixture of mesenteric inflammation, fat necrosis, and fibrosis
• Key concepts

image Uncommon, benign, inflammatory process involving mesenteric fat
image Classified histologically into 3 types or stages based on predominant tissue type in mass

– Mesenteric panniculitis: Acute inflammation ± fat necrosis > fibrosis
– Mesenteric lipodystrophy: Fat necrosis > inflammation or fibrosis
– Retractile mesenteritis: Fibrosis/retraction > inflammation or fat necrosis
image Retractile mesenteritis

– Considered as final, chronic form, with collagen deposition, fat necrosis, fibrosis, and tissue retraction
image Often associated with other idiopathic inflammatory disorders (> 1 condition may be present)
image May coexist with malignancy (e.g., lymphoma, breast, lung, colon cancer, and melanoma)

CT Findings

• Acute mesenteritis (mesenteric panniculitis and lipodystrophy)

image Often associated with misty mesentery: Increased attenuation of mesentery with fat stranding and induration

– Nonspecific finding that can be seen with other etiologies
– Usually located in left upper quadrant mesentery
– Often discrete fat-attenuation “mass” with increasing soft tissue component as disease progresses
image Thin (usually < 3 mm) pseudocapsule encasing inflamed portion of mesentery (tumoral pseudocapsule sign)
image Cluster of mesenteric nodes (only rarely enlarged > 1 cm) within misty mesentery

– Mesenteric vessels and nodes have halo of surrounding spared fat (fat ring or fat halo sign)
• Chronic phase (retractile mesenteritis)

image Chronic fibrosis results in discrete fibrotic soft tissue mass with desmoplastic reaction

– Usually located in root of mesentery (left upper quadrant)
– Mass often has “stellate” appearance with internal calcification (and within adjacent lymph nodes)

image Can rarely show internal cystic or necrotic components
– Encasement of mesenteric and collateral vessels with frequent narrowing/occlusion of portomesenteric veins

image Collaterals or engorged vessels may be present
image Small bowel wall edema and mucosal hyperemia as result of lymphatic/venous obstruction and ischemia
– Tethering of bowel loops can lead to bowel obstruction

MR Findings

• Variable signal intensity due to varying elements of inflammation, fat necrosis, calcification, and fibrosis
• Acute mesenteritis (panniculitis and lipodystrophy)

image T1WI: Mixed signal intensity
image T2WI: Mixed signal intensity (usually mildly hyperintense)
• Chronic phase (retractile mesenteritis): Imaging findings of mature fibrotic reaction

image T1WI: Decreased signal intensity
image T2WI: Very low signal intensity
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