What is mesenteric panniculitis, its typical presentation, diagnostic work‑up, and recommended management?

Mesenteric Panniculitis: Clinical Overview and Management

Definition and Epidemiology

Mesenteric panniculitis (MP) is a benign, chronic inflammatory condition of the mesenteric adipose tissue—most commonly affecting the small bowel mesentery—that is frequently discovered incidentally on abdominal CT imaging and remains asymptomatic in approximately 40–50% of patients. 1, 2

• MP occurs predominantly in men during mid-to-late adulthood, with a reported CT prevalence of 0.6–2.4%, though the true prevalence is likely higher due to underreporting 2, 3
• The condition is characterized histologically by chronic nonspecific inflammation and fibrosis of mesenteric adipose tissue, with unclear etiology 2, 3
• Abdominal trauma and prior abdominal surgery are recognized contributing factors 3

---

Clinical Presentation

Symptomatic Patients (50–60% of cases)

When symptoms occur, they are nonspecific and include:

• Abdominal pain (most frequent symptom) 1, 3
• Bloating or abdominal distention 1
• Diarrhea or constipation 1
• Nausea, vomiting, anorexia, and weight loss 1, 2
• Fever and malaise 1, 2

Asymptomatic Patients (40–50% of cases)

• Most patients are clinically silent and require no intervention 1, 2
• MP is typically identified as an incidental finding during CT imaging performed for unrelated indications 1, 2

---

Diagnostic Work-Up

Imaging: Computed Tomography (First-Line)

CT abdomen is the primary diagnostic modality and demonstrates characteristic findings:

• A mass-like area of increased fat attenuation within the small bowel mesentery, typically in the left upper quadrant 1
• The abnormal mesenteric fat envelops mesenteric vessels (preserving vascular patency) and displaces adjacent bowel loops without causing obstruction 1
• Lymph nodes are frequently present within the area of mesenteric abnormality 1
• The "fat ring sign" (preserved fat halo around vessels and nodes) is a reassuring feature; its absence is associated with higher risk of underlying malignancy 4

Exclusion of Malignancy (Critical Step)

Malignant lymphoma is the most important differential diagnosis and can be difficult to distinguish from MP on CT alone. 1, 2

• Malignancy is identified in approximately 38% of patients with MP, most commonly colorectal cancer, lymphoma, and urogenital malignancies 4
• Lymph nodes >12 mm and absence of the fat ring sign are predictive of subsequent malignancy diagnosis (relative risk 4.5 for large nodes) 4
• PET/CT should be performed if there is clinical or radiological suspicion of concurrent malignancy, particularly when lymph nodes are enlarged or the fat ring sign is absent 1, 4
• In 13 of 45 patients with malignancy in one cohort, the cancer was diagnosed after MP detection, underscoring the need for vigilance 4

Histopathology (Rarely Required)

• Biopsy is not routinely necessary for diagnosis but may be performed if malignancy cannot be excluded by imaging 1, 3
• Histology shows chronic nonspecific inflammation and fibrosis of mesenteric adipose tissue 2, 3

---

Management Algorithm

Asymptomatic Patients (No Treatment Required)

Because MP is a benign condition, asymptomatic patients do not require medical or surgical intervention. 1, 2, 3

• Observation is appropriate, with awareness of potential malignancy association 2, 4
• Routine follow-up imaging is not standardized; clinical judgment should guide surveillance based on initial CT features (e.g., large lymph nodes, absence of fat ring sign) 4

Symptomatic Patients (Medical Therapy)

Treatment decisions should be guided by symptom severity and presence of complications. 1

First-Line Medical Therapy

• Prednisone (glucocorticoids) is effective for symptomatic relief 1, 3
• Tamoxifen is also recommended as first-line therapy, either alone or in combination with corticosteroids 1, 3

Evidence and Rationale

• Glucocorticoids and tamoxifen have been suggested based on case series and clinical experience, though high-quality randomized trials are lacking 2, 3
• The goal is to reduce inflammation and alleviate symptoms such as abdominal pain, nausea, and bloating 1, 3

Surgical Intervention (Reserved for Complications)

Surgery is indicated only for recurrent bowel obstruction, which is a rare complication of MP 1, 3

• In the absence of severe intestinal obstruction, surgical treatment should not be considered 3
• Most patients do not progress to require surgery 1

---

Key Clinical Pitfalls and Caveats

Pitfall 1: Missing Underlying Malignancy

• Do not dismiss MP as purely benign without excluding malignancy, especially lymphoma 1, 2, 4
• Lymph nodes >12 mm and absence of the fat ring sign should prompt PET/CT or biopsy 4
• Approximately one-third of patients with MP have an associated malignancy, and in some cases the cancer is diagnosed after MP detection 4

Pitfall 2: Overtreatment of Asymptomatic Patients

• Asymptomatic MP does not require therapy; avoid unnecessary corticosteroids or tamoxifen in incidental cases 1, 2, 3
• The majority of patients remain clinically silent and have a benign course 2, 3

Pitfall 3: Confusing MP with Acute Mesenteric Ischemia

• MP presents as a chronic, indolent process, whereas acute mesenteric ischemia presents with severe abdominal pain out of proportion to physical exam findings and requires urgent vascular imaging and intervention 5
• MP does not cause acute vascular occlusion or bowel necrosis 1, 3

Pitfall 4: Premature Surgical Referral

• Surgery is reserved only for recurrent bowel obstruction, not for symptom control or diagnostic purposes 1, 3
• Medical therapy with corticosteroids and tamoxifen should be exhausted before considering surgery 1, 3

---

Prognosis

• MP is a benign condition with no impact on mortality in the absence of associated malignancy 1, 2, 3
• Symptomatic patients typically respond well to medical therapy 3
• The clinical relevance of MP remains debated, with recent case-control studies suggesting it is an independent, nonspecific, age-related phenomenon rather than a paraneoplastic syndrome, though the association with lymphoma persists in some cohorts 2, 4