What is mesenteric panniculitis?

Mesenteric Panniculitis

Mesenteric panniculitis is a rare, benign inflammatory condition characterized by chronic inflammation and fibrosis of adipose tissue primarily affecting the small bowel mesentery. 1

Definition and Pathophysiology

• Mesenteric panniculitis (MP) is a non-neoplastic idiopathic inflammation of the adipose tissue of the mesentery, most commonly affecting the small intestine mesentery 2
• It represents a spectrum of disease with two pathological subgroups: Mesenteric Panniculitis (where inflammation and fat necrosis predominate) and Retractile Mesenteritis (where fibrosis and retraction predominate) 3
• The specific etiology remains unknown, though various theories exist regarding potential triggers 4

Clinical Presentation

• MP is often asymptomatic and discovered incidentally on abdominal imaging in up to nearly half of patients 1
• When symptomatic, the most common presentation is abdominal pain, followed by:
  • Bloating/distention
  • Diarrhea
  • Constipation
  • Vomiting
  • Anorexia
  • Weight loss
  • Fever
  • Malaise
  • Nausea 1

Diagnostic Features

Imaging Findings

• Computed tomography (CT) is the primary diagnostic tool, showing characteristic features:
  • Mass-like area of increased fat attenuation within the small bowel mesentery, typically in the left upper quadrant 1
  • Well-defined "mass effect" on neighboring structures 3
  • Mesenteric fat tissue of inhomogeneous higher attenuation than adjacent fat 3
  • Small soft tissue nodes within the affected area 3
  • Hypoattenuated fatty "halo sign" (specific but inconstant) 3
  • Hyperattenuating pseudocapsule surrounding the entity (specific but inconstant) 3
  • Envelopment of mesenteric vessels and displacement of adjacent bowel segments 1

Histopathology

• Deep excisional specimens with large amounts of tissue are required for appropriate histopathological evaluation 3
• Histologically, MP shows:
  • Fat necrosis
  • Chronic inflammation
  • Fibrosis of varying degrees depending on the stage of disease 1

Differential Diagnosis

• The differential diagnosis is extensive and includes:
  • Lymphoma
  • Well-differentiated liposarcoma
  • Peritoneal carcinomatosis
  • Carcinoid tumor
  • Retroperitoneal fibrosis
  • Lipoma
  • Mesenteric desmoid tumor
  • Mesenteric inflammatory pseudotumor
  • Mesenteric fibromatosis
  • Mesenteric edema 3

Treatment Approaches

• Due to the benign nature of MP, treatment decisions should be guided by symptom severity and presence of complications 1
• First-line medical treatment includes:
  • Prednisone (corticosteroids) - typically starting at 40 mg daily 5
  • Tamoxifen 1
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) 2
• Surgical intervention is reserved for:
  • Cases of recurrent bowel obstruction
  • When diagnosis is unclear
  • When malignancy is suspected
  • Severe presentation with mass effect or ischemic changes 1, 2

Prognosis

• The overall prognosis is generally favorable in most cases 3
• Symptoms typically respond to appropriate treatment within weeks to months 5
• Recurrence appears to be rare 5
• Progression from mesenteric panniculitis to retractile mesenteritis is considered very rare and remains doubtful 3

Clinical Pearls and Pitfalls

• MP can mimic more serious conditions like mesenteric ischemia or malignancy, making accurate diagnosis crucial 1
• PET/CT may be useful to correctly exclude mesenteric tumoral involvement in patients presenting with typical MP 3
• The absence of specific diagnostic criteria can lead to misdiagnosis or delayed diagnosis 1
• MP should be considered in the differential diagnosis of patients with nonspecific abdominal symptoms and characteristic CT findings 2