Mesenteric adenitis

Mesenteric adenitis (or mesenteric lymphadenitis) refers to inflammation of the mesenteric lymph nodes, usually in the right lower quadrant of the abdomen. It is a common mimic of acute appendicitis, particularly in children and adolescents, and is often associated with a preceding viral or bacterial infection. Most cases are benign and self-limiting, but recognition is important to avoid unnecessary surgery.

🔬 Etiology & Pathophysiology

• 🦠 Infectious: Most common cause. Viral (e.g. adenovirus, enterovirus) or bacterial (e.g. Yersinia enterocolitica, Campylobacter, Salmonella).
• 🌡️ Post-infectious: Following upper respiratory tract or gastroenteric infections.
• ⚠️ Secondary causes: Can occur with inflammatory bowel disease (Crohn’s, ulcerative colitis), tuberculosis, lymphoma, or other intra-abdominal infections.
• Pathology: Hyperplasia and inflammation of mesenteric lymph nodes, often in the ileocaecal region.

🧩 Clinical Features

• 👶 Typically affects children and adolescents, but adults may be affected.
• 🤕 Abdominal pain – often colicky, centred in right lower quadrant, mimicking appendicitis.
• 🌡️ Fever – usually low-grade, may follow recent viral illness.
• 🚽 Associated symptoms – nausea, vomiting, diarrhoea, anorexia.
• 🫁 Recent sore throat, cough, or other respiratory infection often reported.
• 🩺 Examination – localised RLQ tenderness, but usually less peritoneal irritation than appendicitis.

📊 Differentials

• Acute appendicitis (most important to exclude).
• Intussusception.
• Inflammatory bowel disease (esp. Crohn’s).
• Gastroenteritis.
• Meckel’s diverticulitis.
• Ovarian/testicular torsion in adolescents.

🧪 Investigations

• Bloods: Mild leucocytosis and CRP elevation; often less marked than appendicitis.
• Ultrasound: First-line imaging in children. Shows enlarged, clustered lymph nodes (≥5 mm short axis), absence of appendiceal thickening.
• CT scan (adults): Enlarged mesenteric nodes with a normal appendix, excludes other causes.
• Stool cultures: If enteric bacterial infection suspected (e.g. Yersinia).

💊 Management

• ✅ Supportive care: Most cases are self-limiting within 1–4 weeks.
• 💊 Analgesia & antipyretics: Paracetamol/NSAIDs for pain and fever.
• 💧 Hydration: Encourage oral fluids; IV fluids if unwell.
• 🦠 Antibiotics: Not routinely required unless bacterial infection confirmed or immunocompromised host.
• 🏥 Hospital admission: Consider if diagnosis uncertain, severe pain, systemic features, or complications.

⚠️ Complications

• Rare, but may include:
  • Misdiagnosis leading to unnecessary appendectomy.
  • Chronic/recurrent pain syndromes in a minority of patients.
  • Underlying pathology (e.g. IBD, lymphoma) if persistent.

💡 Teaching Pearls

🔍 Always consider mesenteric adenitis in a child with RLQ pain and a recent viral illness. 🧪 Ultrasound is the investigation of choice – it reduces negative appendectomy rates. 📉 Most cases resolve without treatment – reassurance and follow-up are key. ⚠️ Persistent or atypical cases should prompt evaluation for IBD, TB, or malignancy.