mesenteric panniculitis (MP) / sclerosing mesenteritis

introduction

MP is a rare non-malignant disorder characterised by an acute benign fibrosing and inflammatory condition that involves the adipose tissue of the mesentery of the small bowel primarily, although colon is affected in 20%, and rarely it may involve the omentum, pancreas, mesoappendix and pelvis.
3 sequential phases:
- mesenteric fat necrosis (lipodystrophy)
- chronic non-specific inflammation of adipose tissue (panniculitis)
- fibrosis (sclerosing mesenteritis, retractile mesenteritis)
most commonly presents in the 6th decade, although it can occur in young adults, and affects males 2x as often as females¹⁾
aetiology remains unknown although:
- a history of abdominal trauma or surgery is often present
- tobacco use appears to be a risk factor
it is usually found on CT abdo scan for upper abdominal pain - usually RUQ pain or for fullness or mass in the abdomen.
tends to respond to corticosteroids, colchicine or immunosuppressants
overall, prognosis is usually good and recurrence seems to be rare
mean clinical progression is usually 6 mo, ranging from 2 wk to 16 years²⁾
20% have significant morbidity and a chronic debilitating course
it may be associated with many other conditions including malignancies

most common presentation is of vague symptoms of abdominal fullness and pain in the upper or central abdomen
other symptoms and signs may include:
- anorexia, nausea
- altered bowel habit
- lethargy, fatigue
- vomiting
- diarrhoea
- constipation
- weight loss
- fever of unknown origin
- ascites
- pleural effusion
- pericardial effusion
- rarely:
  - rectal bleeding due to secondary colonic ischaemia
  - gastric outlet obstruction
  - jaundice
  - “acute abdomen”

occasional patients have mildly raised inflammatory markers in the retractile mesenteritis phase (eg. neutrophilia, erythrocyte sedimentation rate (ESR), C reactive protein (CRP))
tumour markers (CEA and CA 19-9) are usually normal unless there is associated malignancy

CT scan is usually diagnostic
CT changes consistent with MP include encapsulated, heterogeneous masses localised to the root of the mesentery or adjacent intestinal loops
most have a left-sided orientation of disease with scattered, well-defined soft tissue nodules of < 5 mm
many have a 'pseudotumoral stripe' of tissue surrounding the mass lesion which may be seen in conjunction with mesenteric vessels which are surrounded or displaced by fat but not invaded³⁾

surgery is of no therapeutic benefit but some patients are referred for laparoscopy and biopsy to exclude neoplasia / cancer / tumours, particularly if there are enlarged mesenteric lymph nodes which raises possible other neoplastic and inflammatory differentials

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