Sclerosing mesenteritis is an idiopathic, chronic, non-neoplastic inflammatory and fibrotic process of mesenteric fat tissue. Mesenteric panniculitis (inflammatory predominant), mesenteric lipodystrophy (fat necrosis predominant), and retractile mesenteritis (fibrosis predominant) represent different stages of the same disease spectrum. The most characteristic CT findings are 'misty mesentery' (hazy increased density of mesenteric fat), 'fat ring sign' (preserved fat ring around mesenteric vessels), and 'tumoral pseudocapsule' (thin soft tissue capsule around the inflammatory mass). Typically seen in males over 50-60 years. Most cases are asymptomatic and discovered incidentally. Treatment with corticosteroids and tamoxifen may be effective.
Age Range
40-80
Peak Age
60
Gender
Male predominant
Prevalence
Uncommon
Sclerosing mesenteritis is a chronic inflammatory process that begins idiopathically in mesenteric fat tissue. Pathogenesis is not fully understood but autoimmune mechanisms, ischemic injury, prior surgery, or infection may be triggers. Histologically three components coexist: (1) fat necrosis — lipocyte degeneration and foamy macrophage infiltration, (2) chronic inflammation — lymphocyte and plasma cell infiltration, (3) fibrosis — collagen accumulation and fibrotic bands. The 'misty mesentery' finding on CT reflects increased density of mesenteric fat due to inflammatory edema and cell infiltration — normal mesenteric fat density is -100 to -130 HU, rising to -40 to -60 HU in affected areas. 'Fat ring sign' results from preserved normal fat layer around mesenteric vessels not being affected by the inflammatory process — preservation of perivascular fat is a specific feature of sclerosing mesenteritis distinguishing from peritoneal carcinomatosis. 'Tumoral pseudocapsule' represents reactive fibrous tissue accumulation around the inflammatory mass.
Preserved normal fat ring around mesenteric vessels on CT — perivascular fat layer unaffected by inflammatory process. Presence of this preserved fat ring in the setting of misty mesentery is considered pathognomonic for sclerosing mesenteritis and distinguishes from carcinomatosis.
Diffuse hazy density increase in mesenteric fat on CT — 'misty mesentery' finding. Normal mesenteric fat density is -100 to -130 HU, rising to -40 to -60 HU in affected areas. This density increase may be homogeneous or mildly heterogeneous. Mesenteric root (jejunal mesentery) is the most commonly affected area.
Report Sentence
Diffuse hazy density increase is seen at the mesenteric root and jejunal mesentery (misty mesentery); consistent with sclerosing mesenteritis.
Preserved normal fat ring around mesenteric vessels (SMA/SMV branches) — 'fat ring sign.' While the inflammatory process affects mesenteric fat, the perivascular fat layer is preserved creating a hypo-dense halo around vessels. This finding is highly specific for sclerosing mesenteritis and distinguishes from carcinomatosis.
Report Sentence
Preserved normal fat ring around mesenteric vessels is seen (fat ring sign); this finding is pathognomonic for sclerosing mesenteritis.
Thin (1-3 mm), smooth-contoured, enhancing soft tissue capsule around the inflammatory mass — 'tumoral pseudocapsule.' This capsule defines the boundary of the inflammatory process with surrounding normal tissue. Pseudocapsule presence reflects the fibrotic stage of sclerosing mesenteritis.
Report Sentence
A thin, smooth-contoured pseudocapsule is seen around the inflammatory mass; supports the fibrotic stage of sclerosing mesenteritis.
Affected mesentery shows heterogeneous signal on T2-weighted images — inflammatory areas hyperintense (edema and cell infiltration), fibrotic areas hypointense (collagen accumulation). Fat ring sign can also be seen on MRI — perivascular fat maintains hyperintense signal on T1 and T2. Pseudocapsule is seen as a hypointense ring on T2.
Report Sentence
Heterogeneous signal is shown in the mesentery on T2-weighted sequence — hyperintense inflammatory and hypointense fibrotic areas coexisting; consistent with sclerosing mesenteritis.
Mass-like soft tissue area with hazy density increase at the mesenteric root on non-contrast CT. Calcification is rare. Significantly different from normal mesenteric fat density (-40 to -60 HU vs normal -100 to -130 HU). Small well-defined lymph nodes may accompany.
Report Sentence
Mass-like hazy density increase is seen at the mesenteric root on non-contrast CT; may be consistent with sclerosing mesenteritis.
Hyperechoic, heterogeneous, well-defined mass at the mesenteric root on US. Appears more echogenic than normal mesenteric fat. Minimal vascularity on Doppler. Bowel loops may be displaced by the mass.
Report Sentence
A hyperechoic, heterogeneous mass is seen at the mesenteric root; may be consistent with sclerosing mesenteritis.
Criteria
Inflammation predominant. Lymphocyte and macrophage infiltration dominant. Misty mesentery prominent on CT. Asymptomatic or abdominal pain. Self-limited.
Distinct Features
Most prominent misty mesentery on CT; fat ring sign positive; pseudocapsule may not yet be formed.
Criteria
Fibrosis predominant. Collagen accumulation and mesenteric retraction dominant. Risk of bowel obstruction. May require treatment.
Distinct Features
Pseudocapsule prominent on CT; mesenteric retraction and bowel kinking; hypointense areas on T2 MRI (fibrosis).
Criteria
Fat necrosis predominant. Foamy macrophage infiltration dominant. Focal fat necrosis nodules in the setting of misty mesentery on CT. Earliest histological stage.
Distinct Features
Small soft tissue nodules in the setting of misty mesentery on CT; fat ring sign positive; pseudocapsule absent or minimal.
Distinguishing Feature
In carcinomatosis fat ring sign is absent, peritoneal nodules are irregular and large, ascites is prominent; in sclerosing mesenteritis fat ring sign is positive, nodules are small and well-defined.
Distinguishing Feature
Lymphoma shows discrete enlarged lymph nodes and sandwich sign; sclerosing mesenteritis shows diffuse misty mesentery and fat ring sign — different morphological patterns.
Distinguishing Feature
Lipoma is an encapsulated mass at homogeneous fat density (-80 to -120 HU); sclerosing mesenteritis shows diffuse misty mesentery (-40 to -60 HU) and is not encapsulated.
Distinguishing Feature
TB peritonitis shows peritoneal thickening, ascites and necrotic lymph nodes; sclerosing mesenteritis shows misty mesentery, fat ring sign and non-necrotic small nodules.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthSclerosing mesenteritis is generally benign, self-limited, and most cases are asymptomatic. Biopsy may be needed for differential diagnosis from carcinomatosis and lymphoma — especially if fat ring sign is absent or atypical findings are present. Corticosteroids and tamoxifen are effective in symptomatic cases. Surgery may be needed if bowel obstruction develops. Prognosis is generally good and spontaneous regression may occur. Follow-up with CT every 6-12 months is sufficient to assess treatment response.
Sclerosing mesenteritis is generally benign and may not require treatment. Corticosteroids or tamoxifen can be used in symptomatic patients. Biopsy may be needed to differentiate from lymphoma and carcinoid. Fat ring sign and misty mesentery strongly support diagnosis.