Mesenteric Panniculitis

Mesenteric panniculitis is a chronic non specific inflammation of mesenteric adipose tissue, typically in the small bowel mesentery root, representing the early inflammatory stage of sclerosing mesenteritis.

• Incidence is about 0.6% on abdominal CT; men are affected twice as often as women; mean age 60 years.
• Associations: abdominal surgery or trauma, autoimmune disease, IgG4 related disease, vasculitis, previous infection, malignancy (lymphoma, solid tumours, in up to 30% of cases), ischaemia, panniculitis.
• Pathology: fat necrosis, foamy macrophages, lymphocytes, plasma cells; progression to fibrosis in sclerosing mesenteritis.
• Course is usually benign with spontaneous regression; a minority develop bowel obstruction or ischaemia.

• Many are asymptomatic, found incidentally on CT.
• Abdominal pain (50 to 70%), distension, nausea, vomiting, diarrhoea or constipation, fever, malaise, weight loss, early satiety.
• Palpable abdominal mass in a few.
• Complications: bowel obstruction, mesenteric ischaemia, chylous ascites, lymphoedema.
• Red flags: weight loss, night sweats, lymphadenopathy suggesting lymphoma.

• CT abdomen: "misty mesentery" (increased attenuation of mesenteric fat), preserved fat halo around mesenteric vessels (fat ring sign), small lymph nodes (under 1 cm) within the mesentery, hypoattenuating halo, and pseudocapsule.
• Laboratory: CRP, ESR (raised), full blood count, LDH, IgG4, autoimmune screen (ANA, ANCA), tumour markers if indicated.
• Biopsy (CT guided or laparoscopic) in doubtful cases: fat necrosis, chronic inflammation, foamy macrophages.
• Exclude lymphoma, carcinoid, carcinomatosis, mesothelioma, tuberculosis, Crohn disease, pancreatitis with PET CT, endoscopy, and lymph node biopsy.
• Follow up CT at 3 to 6 months to confirm stability or regression.

• Asymptomatic: observation, with follow up CT in 3 to 6 months. Evaluate for malignancy if risk factors.
• Symptomatic mild disease: NSAIDs for pain, dietary advice.
• Corticosteroids: prednisolone 0.5 to 1 mg/kg daily (maximum 60 mg) for 4 to 8 weeks, then taper over 2 to 3 months.
• Steroid sparing or refractory disease: azathioprine 2 mg/kg, low dose naltrexone 4.5 mg at night, colchicine 0.6 mg twice daily, tamoxifen 10 to 20 mg twice daily, cyclophosphamide, infliximab or rituximab (IgG4 related disease) in severe cases.
• Antibiotics (metronidazole, ciprofloxacin) have anecdotal benefit.
• Surgery is reserved for obstruction, ischaemia or perforation; resection is difficult due to mesenteric vascular involvement.
• Surveillance for malignancy for at least 1 to 2 years.