Mesenteric panniculitis BEN ROMDHANE MH Hopital AVICENNE BOBIGNY

Mesenteric panniculitis inflammatory disorder of the fatty tissue of the bowel mesentery Uncommon several names( resulting in considerable confusion ): lipodystrophy, mesenteric Weber-Christian disease, fibrosing mesenteritis, sclerosing mesenteritis retractile mesenteritis

varied terminology reflects the pathological spectrum now considered to be one single disease chronic nonspecific inflammatory process in the mesentery rarely may lead to fibrosis and retraction If inflammation predominates over fibrosis the process is known as mesenteric panniculitis when fibrosis and retraction predominate, terms: fibrosing mesenteritis, retractile mesenteritis or sclerosing mesenteritis are more commonly used

MP supposed to be very rare, approximately 250 cases reported in the literature With increased use of abdominal diagnostic imaging, MP is diagnosed more often Recently reported prevalence of 0.6% of all patients undergoing an abdominal CT for various indications

Pathogenesis infiltration of mesenteric fat by : inflammatory cells, mainly lymphocytes and fat-laden macrophages with inflammation, a mixture of fat necrosis and fibrosis may be present in the mesentery exact cause remains unclear

MP occurs independently or in association with other disorders A variety of possible causative factors have been proposed: autoimmune disorders ischemia prior abdominal surgery

also suggested paraneoplastic response This possible association with a concomitant malignancy highlighted in a study by Daskalogiannaki reporting the presence of a coexisting abdominal or distal malignancy in 69% of patients with CT features of MP In other studies prevalence of malignancy not different from general population of patients undergoing CT for all various indications

Clinical characteristics mostly middle or late adulthood, male predominance. Clinical manifestations may be related to the inflammation or to mass-effect Presenting symptoms may vary may also be entirely asymptomatic commonly include non-specific abdominal pain Palpable abdominal mass may be present may lead to the clinical misdiagnosis (aortic aneurysm ...)

Laboratory findings: often within the normal range or demonstrate non-specific findings: mild leucocytosis and elevation of the erythocyte sedimentation rate. before the advent of modern diagnostic imaging, MP was diagnosed exclusively as an unexpected finding at exploratory laparotomy or autopsy

Diagnosis A definite diagnosis of MP can be made only by pathologic analysis However, the incidental benign and often asymptomatic nature of MP usually does not justify biopsy In these cases, diagnosis may be suggested by characteristic imaging features from the radiological literature from pathologically proven cases

US features often quite subtle may be easily overlooked poorly defined hyperechoic change of the mesenteric fat decrease in mesenteric compressibility may be seen in various conditions with mesenteric involvement( lipomatous tumors... CT always recommended to analyze any US-found mesenteric abnormalities

A. C. van Breda Vriesman Eur Radiol (2004)

CT features increased density of mesenteric fatty tissue (approximately− 40 to −60 HU) compared to the attenuation values of normal retroperitoneal or subcutaneous fat (−100 to −160 HU) hyperattenuating fat surrounds mesenteric vessels but does not displace them some regional mass-effect by displacing locally small bowel loops mass most frequently located at the left side corresponding to jejunal mesentery

Piessen G Annales de chirurgie 131 2006

Other CT features reported may be valuable clues for the diagnosis: the fat-ring sign, tumoral pseudocapsule soft-tissue nodules

Fat-ring sign Fat-ring sign or “fatty halo 75–85% low-density fat surrounding vessels and nodules preservation of normal fat density, corresponding to unaffected noninflamed fat interposed between vessels or nodules and inflammatory cells at histopathology non-specific also reported incidentally in non-Hodgkin’s lymphoma in which chemotherapy treatment has led to reduction of the mesenteric lymphadenopathy, leaving a fine haziness throughout the mesenteric fat

Tumoral pseudocapsule peripheral band with soft-tissue attenuation limiting the inflammatory mesenteric mass thickness of this dense stripe usually does not exceed 3 mm reported in 50–59% of patients lipomatous tumor (lipoma or liposarcoma) may be well-defined by a similar dense rim but these lesions will often show some mass-effect on the mesenteric vessels in contrast to M P

A. C. van Breda Vriesman Eur Radiol (2004)

Soft-tissue nodules small soft-tissue nodules scattered within the hyperattenuating mesenteric mass in 80% of cases Correspond probably to lymph nodes usually less than 5 mm in diameter Mesenteric lymph nodes larger than 10 mm atypical for MP biopsy or fine-needle aspiration must be considered to exclude malignancy

SM most commonly appears as a soft-tissue mass in the small bowel mesentery The mass may envelop the mesenteric vessels, and collateral vessels Mesenteric thickening and fibrosis often with nodular masses involving the appendices epiploicae of the colon

Calcification may be present, usually in the central necrotic portion of the mass it may be related to the fat necrosis Cystic components also described may be the result of lymphatic or venous obstruction and necrotic change Enlarged mesenteric or retroperitoneal lymph nodes may be present

Farzana Nawaz Ali, Case Reports in Medicine2010

Farzana Nawaz Ali, Case Reports in Medicine 2010

Imaging-based differential diagnosis misty mesentery :Alteration in the density of the mesenteric fat on CT with an extensive differential diagnosis MP reserved for idiopathic inflammation leading to a misty mesentery

imaging diagnosis can therefore be made only after exclusion of any of the following alternative causes of a misty mesentery

Mesenteric edema Many causes heart failure, portal hypertension, mesenteric vascular thrombosis and lymphedema. mesenteric edema secondary to a systemic disease, usually associated with generalized subcutaneous edema and ascites. Ascites is not a feature of MP and indicates an alternative diagnosis

Inflammation acute pancreatitis is the typical inflammatory process associated with increased CT density of the mesenteric fat usually centered in the peripancreatic region With usually increased levels of amylase in serum and urine enabling the diagnosis Focal inflammations such as appendicitis and colonic diverticulitis may also cause local hyperattenuation of adjacent mesenteric fat these diagnoses must be carefully ruled out

Mesenteric Hemorrhage hemorrhage, caused by blood dissecting from mesenteric vessels or from the bowel wall may be traumatic or spontaneous A history of trauma, use of anticoagulantia or high-density peritoneal fluid suggests the correct diagnosis

Neoplasm Non-Hodgkin’s lymphoma most common mesentery tumor Typically bulky lymphadenopathy, often also n the retroperitoneum, indicating the correct diagnosis Shrinkage of mesenteric lymphadenopathy after chemotherapy may result in residual scarring that may mimic MP Needs reviewing the patient’s prior CT scans

lymphoma manifested as nodal mass in the root of the mesentery may mimic SM no calcification unless previously treated Both can encase mesenteric vasculature lymphoma almost never result in ischemia fat halo sign favors a diagnosis of SM large, nodes favor lymphoma Treated lymphoma may also produce a misty mesentery simulating the MP

Primary mesenteric neoplasms (desmoid, mesenteric cyst, lipomatous tumors) cause mass-effect on mesenteric vessels Other tumors :mesothelioma, or metastatic tumors:( pancreatic, colon or ovarian carcinoma ) may affect the mesentery by soft-tissue tumor deposits, or may cause mesenteric edema by lymphatic obstruction correct diagnosis made by identification of the primary tumor or detection of extra-mesenteric peritoneal nodules, or by cytological analysis of ascites

A. C. van Breda Vriesman Eur Radiol (2004)

Carcinoid tumor may simulate SM ill-defined, infiltrating soft-tissue mass in the root of the mesentery with calcification and desmoplastic reaction fat ring sign favors a diagnosis of SM enhancing mass in bowel wall or hypervascular liver metastases : sign diagnosis of carcinoid tumor

primary mesenteric mesothelioma can produce mesenteric soft-tissue implants in mesentery, also seen in the omentum and along the bowel surfaces. Ascites not associated with SM Calcification not common

Treatment Treatment usually empirical may consist of steroids, colchicine, immunosuppressive agents, or orally administered progesterone In SM Surgical resection difficult due to vessel compromise may be of no clear benefit colostomy may be necessary with colonic involvement by SM

Variable course With treatment: relatively benign course progression of the disease eventually leads to death In some cases, complete resorption

CT suggest the diagnosis of SM CT useful in distinguishing SM from other mesenteric diseases such as lymphoma or carcinoid tumor Biopsy necessary for SM diagnosis CT optimal study for the follow up