What is the best investigation for a patient presenting with pus and discharge from the umbilicus (navel)?

Best Investigation for Umbilical Discharge

Abdominal ultrasound is the best initial investigation for a patient presenting with pus and discharge from the umbilicus. 1

Diagnostic Approach for Umbilical Discharge

First-Line Investigation: Abdominal Ultrasound

• Recommended by the American College of Radiology as the initial investigation due to:
  • Non-invasive nature
  • Absence of radiation exposure
  • Cost-effectiveness
  • Ability to visualize fluid collections, abscesses, and underlying causes 1
• Can effectively identify:
  • Umbilical abscesses
  • Fluid collections
  • Potential embryological remnants (urachal or omphalomesenteric duct remnants)
  • Umbilical hernias with complications
  • Surrounding soft tissue inflammation 1

Second-Line Investigations (if ultrasound findings are inconclusive):

1. CT with IV contrast:

   • Indicated when better anatomical detail is needed
   • Sensitivity of 77% for diagnosing abscesses
   • Essential for delineating rim enhancement of abscess
   • Helpful in identifying fistulous tracts 1
   • Protocol should include:
     • Coverage of entire area of interest
     • 2-3mm slice thickness
     • IV contrast with imaging 50-70 seconds post-injection 1

2. MRI:

   • Superior for evaluating complex cases and fistula tracts
   • Consider for patients with suspected complex fistulous connections 1

3. Fistulogram:

   • Only recommended if there is a specific suspicion of fistulous connection that cannot be characterized by cross-sectional imaging 1
   • Limited utility as a first-line investigation

4. Abdominal X-ray:

   • Limited value in evaluating umbilical discharge 1
   • Not recommended as an initial investigation

Clinical Implications and Management

Common Underlying Causes to Consider

• Urachal remnants (connecting umbilicus to bladder) 2
• Patent vitello-intestinal duct 3
• Umbilical granuloma 3
• Umbilical hernia with fat necrosis 4
• Omphalitis (inflammation of the umbilicus) 2
• Rarely, abdominal tuberculosis 5 or malignancy 4

Management Approach

• Primary treatment is surgical incision and drainage, with timing based on sepsis severity 1
• For abscesses >3-4cm, surgical drainage is essential 1
• Empiric antibiotics should cover gram-negative bacteria and anaerobes 1
• Complete excision of underlying cause (e.g., urachal remnant) is often necessary to prevent recurrence 2, 3

Important Considerations and Pitfalls

• Pitfall #1: Relying solely on clinical examination may miss important underlying causes such as embryological remnants or fistulas 1
• Pitfall #2: Incomplete drainage is associated with high recurrence rates (up to 44%) 1
• Pitfall #3: Missing the underlying cause can lead to recurrence if not identified and treated 1, 3
• Pitfall #4: Delayed intervention, especially in immunocompromised patients, can lead to severe infection despite minimal symptoms 1
• Pitfall #5: Point-of-care ultrasound, while useful, is operator-dependent with variable results and limited ability to assess deep tissue spaces 1

Abdominal ultrasound should be performed promptly in patients with umbilical discharge to guide appropriate management and identify potential underlying causes that require surgical intervention.