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Sclerosing mesenteritis

Sclerosing mesenteritis is an uncommon idiopathic disorder characterised by chronic non-specific inflammation involving the adipose tissue of the bowel mesentery 1.

Epidemiology  

Typically this condition afflicts adults in their 60s with mild male predilection although reports vary 1,2,4.

Clinical presentation

Often sclerosing mesenteritis is asymptomatic, but may present with nonspecific abdominal pain, altered bowel habits, and weight loss. Occasionally, intermittent partial bowel obstruction is encountered 2. A firm left upper quadrant / central abdominal mass may be felt 2.

Pathology

The small bowel mesentery is affected in most cases although the sigmoid mesocolon and omentum can also be occasionally be involved. 

The disease is said to pass through three stages, although some authors believe these to be separate entities 4:

  1. mesenteric lipodystrophy: degeneration of mesenteric fat
  2. mesenteric panniculitis: inflammatory reaction
  3. retractile mesenteritis / sclerosing mesenteritis: fibrosis, which may be associated with distortion or lymphatic obstruction

Macroscopically, the mesentery is thickened with either solitary or multiple focal masses 4.

 It may be related to Weber-Christian disease 2.

Histology

Histology demonstrates 1:

  1. lipid-laden macrophages (mesenteric lipodystrophy)
  2. lymphocytic aggregates and lymphoid follicles (mesenteric panniculitis)
  3. variable amounts of fibrosis (retractile mesenteritis)
Associations

Numerous associated conditions have been variably described including 1,4

  • malignancy
  • recent abdominal surgery 4
  • systemic inflammatory conditions
  • autoimmune conditions (may be related to IgG4-related disease)

There is debate about the association between systemic inflammatory conditions and mesenteric panniculitis. Determining causation is difficult. The term "secondary mesenteric panniculitis" is reserved by some authors for patients with systemic inflammatory conditions. Most authors would not use the term when there is a local cause for mesenteric inflammation.

    Radiographic features

    CT

    CT features are somewhat dependent on the main tissue component and include

    • well-demarcated or ill-defined mesenteric masslike lesion with surrounding "misty" attenuation
    • "misty" soft-tissue attenuation

    The mesentery demonstrates mass effect and may have a ground glass opacity (misty mesentery). Typically the traversing mesenteric vessels and soft tissue nodules have a spared fat halo (this has sometimes been referred to as the fat ring sign). Its orientation is aligned with the root of the jejunal mesentery. Punctate/coarse calcifications (~20%) as well as small lymph nodes (usually <5 mm) may be present within the region.

    Ultrasound

    Ultrasound typically demonstrates distortion and thickening of the root of the mesentery with slight decrease in echogenicity. Mass effect may be evident. 3

    A halo of sparing around vessels may be also seen on ultrasound as a region of hyperechoic fat 3.

    MRI

    Findings are similar to CT. One report describes a fibrous capsule around the inflammation 12.

    FDG PET-CT

    May have high accuracy for the differentiation between

    • sclerosing mesenteritis (or one of its stages): not FDG-avid
    • malignant mesenteric involvement: FDG-avid

    especially in patients with lymphoma 10. If in doubt, biopsy may be indicated in selected patients, even in asymptomatic lesions 11.

    Treatment and prognosis

    The mainstay of treatment is supportive, as the disease is typically self limiting. If severe or protracted medical therapy with corticosteroids, cyclophosphamide or azathioprine can be contemplated 2. Mesenteric panniculitis cannot be completely resected and surgery is of no benefit. In up to 15% of cases, local lymphoma eventually develops 2, 4.

    Differential diagnosis

    General imaging differential considerations include:

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