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

Best Investigation for Umbilical Discharge with Pus

Abdominal ultrasound is the best initial investigation for a patient presenting with pus and discharge from the umbilicus due to its non-invasive nature, lack of radiation exposure, and cost-effectiveness. 1

Diagnostic Approach for Umbilical Discharge

First-Line Investigation

• Abdominal Ultrasound (Option B) is recommended by the American College of Radiology as the initial imaging modality because:
  • It can effectively visualize fluid collections and abscesses
  • It can identify potential underlying causes such as:
    • Umbilical abscess
    • Embryological remnants (urachal or vitellointestinal duct remnants)
    • Umbilical hernia with complications
    • Surrounding soft tissue inflammation 1
  • It provides real-time imaging without radiation exposure
  • It is widely available and cost-effective

Second-Line Investigations

If ultrasound findings are inconclusive or a complex fistulous tract is suspected:

• CT with IV contrast should be considered:

  • Has a reported sensitivity of 77% for diagnosing abscesses
  • Provides better anatomical detail of fistulous tracts
  • Protocols should include 2-3mm slice thickness with IV contrast administered 50-70 seconds before imaging 1

• MRI is superior for evaluating:

  • Complex cases with fistulous tracts
  • Soft tissue involvement
  • Patients where radiation exposure is a concern 1

• Fistulogram (Option D) is only recommended in specific scenarios:

  • When there is a suspected fistulous connection that cannot be characterized by cross-sectional imaging
  • Not recommended as a first-line investigation due to its invasive nature and limited field of view 1
  • May be useful in select cases to define the exact anatomy of a known fistulous tract

Limitations of Other Options

• Abdominal X-ray (Option C) has limited value in evaluating umbilical discharge as it cannot adequately visualize soft tissue abnormalities or fluid collections 1

Clinical Implications

Common Causes of Umbilical Discharge

• Umbilical abscess
• Embryological remnants:
  • Patent urachus 2
  • Patent vitellointestinal duct 3
• Umbilical hernia with complications 4
• Umbilical granuloma 3
• Rarely, abdominal tuberculosis 5 or malignancy 4

Management Considerations

• Primary treatment typically involves surgical incision and drainage, with timing based on sepsis severity
• For abscesses >3-4cm, surgical drainage is essential
• Empiric antibiotics should cover gram-negative bacteria and anaerobes 1
• Incomplete drainage is associated with high recurrence rates (up to 44%)
• Missing the underlying cause can lead to recurrence if not identified and treated 1

Pitfalls to Avoid

• Relying solely on clinical examination may miss important underlying causes such as embryological remnants or fistulas
• Delayed intervention, especially in immunocompromised patients, can lead to severe infection despite minimal symptoms
• Point-of-care ultrasound, while useful to confirm fluid collection, is operator-dependent with variable results and limited ability to assess deep tissue spaces 1
• Treating only the abscess without addressing the underlying cause (such as a urachal remnant) often leads to recurrence 2, 3

In conclusion, abdominal ultrasound should be the first investigation for a patient with umbilical discharge and pus, with CT, MRI, or fistulogram reserved for cases requiring further evaluation of complex anatomy or fistulous tracts.