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 (US) is the best initial investigation for a patient presenting with pus and discharge from the umbilicus. 1

Rationale for Ultrasound as First-Line Investigation

Abdominal ultrasound offers several advantages as the initial diagnostic tool:

• Non-invasive nature
• Absence of radiation exposure
• Cost-effectiveness
• Ability to effectively visualize:
  • Fluid collections and abscesses
  • Potential embryological remnants (urachal or vitellointestinal duct remnants)
  • Umbilical hernias with complications
  • Surrounding soft tissue inflammation 1

Diagnostic Algorithm for Umbilical Discharge

1. Initial Investigation: Abdominal Ultrasound

   • Provides immediate visualization of fluid collections and abscesses
   • Can identify common causes such as umbilical hernia with fat necrosis 2
   • Detects embryological remnants like patent urachus or vitellointestinal ducts 3, 4

2. Advanced Imaging (if ultrasound findings are inconclusive):

   • CT with IV contrast

     • Better anatomical detail
     • 77% sensitivity for diagnosing abscesses
     • Can identify fistulous tracts
     • Recommended protocol: 2-3mm slice thickness with IV contrast 1

   • MRI

     • Superior for evaluating complex cases
     • Best for detailed visualization of fistulous tracts
     • Particularly useful when suspecting complex pathology 1

   • Fistulogram

     • Limited utility - only recommended if specific suspicion of fistulous connection exists that cannot be characterized by cross-sectional imaging
     • Not recommended as first-line investigation 1, 4

Common Pitfalls to Avoid

1. Relying solely on abdominal X-ray

   • Limited value in evaluating umbilical discharge
   • May miss important underlying causes 1

2. Delaying advanced imaging

   • Incomplete evaluation can lead to missed diagnoses like embryological remnants or fistulas
   • Particularly dangerous in immunocompromised patients where minimal symptoms may mask severe infection 1

3. Treating without identifying underlying cause

   • High recurrence rates (up to 44%) with incomplete diagnosis and treatment
   • Important to identify conditions like urachal remnants that require surgical excision 3, 4

4. Overlooking serious underlying conditions

   • Umbilical discharge can be a presentation of rare but serious conditions like abdominal tuberculosis 5
   • Metastatic malignancy can also present with umbilical discharge 2

Treatment Considerations

After appropriate imaging and diagnosis:

• Primary treatment typically involves surgical incision and drainage
• Empiric antibiotics covering gram-negative bacteria and anaerobes should be started
• Complete excision of any embryological remnants is necessary to prevent recurrence 1, 4
• Follow-up imaging is indicated in cases of recurrence, suspected inflammatory bowel disease, evidence of fistula formation, or non-healing wound 1

Ultrasound provides the best balance of accessibility, safety, and diagnostic utility for the initial evaluation of umbilical discharge, with more advanced imaging reserved for complex or unclear cases.