Mesenteric disease

Mesenteric cysts

Pathophysiology
- Most commonly mesothelial cysts
- Duplication cyst - see separate topic
- 60% small bowel mesentery, 40% colon mesentery
Presentation
- Abdominal pain, fever, vomiting
Management
- Enucleation generally effective, as local vasculature is not adherent to cyst wall
- Internal drainage into the peritoneal cavity has been successfully used to very large cysts
- Aspiration alone has a high rate of recurrence
- Need to examine the cyst wall carefully and biopsy it if you aren't going to excise it

Acute mesenteric lymphadenitis

A syndrome of acute right lower quadrant abdominal pain associated with mesenteric lymph node enlargement and a normal appendix
Epidemiology
- Most common in children and young adults
- Male and female equally
Pathophysiology
- Numerous implicated causative organisms
  - Viral
  - Bacterial
    - Yersinia enterocolitica
  - Parasitic
  - Fungal
Presentation
- Often acute periumbilical pain which shifts to RIF
- Can see RIF guarding and peritonism
- Nausea, vomiting, diarrhoea, and anorexia may be present
- WCC may be elevated
- Fever may be present
- Usually differentiated from appendicitis with ultrasound
Management
- Self-limiting

Sclerosing mesenteritis aka mesenteric panniculitis

A rare, non-neoplastic inflammatory and fibrotic condition affecting the small bowel mesentery

Epidemiology
- Twice as common in men
- Usually 40-50yo
Aetiologies (proposed)
- Abdominal surgery or trauma
- Autoimmunity
- Paraneoplastic syndrome
- Ischaemia and infection
Pathophysiology
- Most often involves the root of the small bowel mesentery and frequently encompasses the mesenteric vessels
- Retracts and shortens the mesentery of the small bowel without directly involving small bowel. Can lead to mesenteric venous and lymphatic obstructions.
- Gross appearance - marked thickening of the mesentery of the small intestine with irregular areas of discolouration suggesting fat necrosis. There may be multiple discrete nodules on the mesentery or it may be a single matted mass.
- Histologically - sclerosing fibrosis, fat necrosis with lipid-laden macrophages, chronic inflammation with germinal centres, and focal calcification
  - Early - develops with a loose myxomatous appearance that progresses to chronic inflammation and dense sclerosis
Presentation
- Mostly asymptomatic, found incidentally on imaging
- Can lead to abdominal pain or symptoms of obstruction
- Abdominal mass palpable in >50% of patients
- ESR and CRP may be elevated (80%)
Imaging
- CT findings:
  - 'Misty mesentery'
  - A fatty mass arising from the base of the mesentery, with well-delineated margins separating it from normal mesentery - 'tumoural pseudocapsule'
  - Normal adipose tissue surrounding mesenteric vessels - 'fat ring sign'
  - Normal mesenteric vessels coursing through the fatty mass, without evidence of vascular involvement or deviation
  - An intra-abdominal mass that displaces adjacent bowel loops without invading them
Differential diagnosis
- Any condition that alters the density of mesenteric fat
- Inflammatory
- Neoplastic
  - NHL - look for retroperitoneal lymphadenopathy, splenomegaly, and lack of tumoural calcification. Less likely if fat ring is present.
  - Neuroendocrine tumours with desmoplastic reactions - look for focal bowel/hepatic lesions
  - Peritoneal carcinomatosis
  - Desmoid tumours - paucity of inflammation
  - Peritoneal carcinomatosis
  - Mesenteric and retroperitoneal sarcomas
- Fluid (oedema, blood, lymph)
- Fibrosis
Diagnosis
- Surgical biopsy is generally necessary for definitive diagnosis
Management
- Mostly improve spontaneously
- Corticosteroids and anti-inflammatories have been found to improve symptoms and radiologic findings
- Often repeat CT in 6/12 if no signs of the above underlying diseases
- Consider biopsy if there is anything to biopsy
- Operative management
  - Diagnostic confusion
  - SBO