How should a fistula at the Bacillus Calmette‑Guérin (BCG) inoculation site be managed?

Management of BCG Inoculation Site Fistula

A fistula at the BCG vaccination site requires immediate evaluation to distinguish between a severe local reaction and disseminated BCG infection, with management ranging from observation for self-limited reactions to surgical drainage plus anti-tuberculous therapy for complicated cases.

Initial Assessment and Risk Stratification

When evaluating a BCG site fistula, the critical first step is determining whether this represents an isolated local complication or early manifestation of systemic disease:

• Evaluate for systemic symptoms including fever, bone pain, joint swelling, or signs of disseminated infection 1
• Assess immunocompetent status, including HIV testing if not previously done, as HIV infection significantly increases risk for lymphadenitis and disseminated complications 1
• Determine timing: Reactions persisting beyond 3 months post-vaccination warrant careful evaluation for complications 1
• Critical pitfall: Persistent reactions at 4 months should never be dismissed as normal and require evaluation for complications including BCG osteitis or disseminated infection 1

Management Algorithm Based on Clinical Presentation

For Isolated Local Fistula Without Systemic Signs

Adherent or fistulated lymph nodes may require drainage and direct instillation of anti-tuberculous drug into the lesion 1. The approach depends on the characteristics of the fistula:

• Nonadherent lymph nodes heal spontaneously without treatment 1
• Fistulated nodes require active intervention with drainage 1
• Monitor closely for progression to systemic involvement 1

For Suspected Disseminated Disease or Systemic Involvement

Anti-tuberculous therapy must be initiated immediately when systemic BCG infection is suspected 1:

• Drug regimen: Use isoniazid, rifampicin, and ethambutol as the standard three-drug combination 2, 3
• Critical contraindication: Never use pyrazinamide, as all BCG strains are universally resistant to this agent 1
• Duration: Treatment typically requires 3 months for localized infections 4, but may extend to 15 months or longer depending on symptom severity and response 2
• At least two first-line drugs active against M. bovis should be used (isoniazid, rifampicin, or ethambutol) 3

Surgical Intervention Considerations

Surgery becomes necessary when conservative management fails:

• Indications for surgery: If symptoms of BCG infection are not controlled with medical therapy, surgical intervention may be required even for non-life-threatening complications 2
• Drainage procedures: Fistulated lesions may require incision and drainage with direct instillation of anti-tuberculous medication 1
• In severe cases affecting quality of life that don't respond to prolonged anti-tuberculous therapy, more extensive surgical resection may be necessary 2

Diagnostic Workup

Obtain cultures before initiating antibiotics to guide definitive therapy:

• Collect samples from any exudate at the fistula site for Gram staining, routine bacterial culture, and mycobacterial culture 5
• Important caveat: Tissue cultures for BCG are notoriously difficult to grow, making definitive diagnosis challenging 2
• Draw at least 2 sets of blood cultures if systemic signs are present 5
• Consider imaging studies, as abnormal imaging and laboratory tests are common findings in both probable and proven BCG infections 3

Adjunctive Therapy

Corticosteroids may be beneficial in systemic BCG infections 3, 6:

• Approximately 36% of patients with BCG infection receive steroids as part of treatment 3
• Consider corticoids particularly for severe systemic manifestations 6

Key Clinical Pitfalls to Avoid

• Do not delay evaluation: A red and enlarged BCG vaccination site at 4 months post-vaccination requires evaluation for severe local reaction or early manifestation of BCG osteitis or disseminated infection 1
• Do not use pyrazinamide: This is universally ineffective against BCG strains and should never be included in treatment regimens 1
• Do not underestimate treatment duration: BCG infections require significantly longer treatment courses than typical bacterial infections, sometimes extending beyond one year 2
• Do not miss immunocompromised status: HIV testing should be considered in any patient with prolonged or severe BCG reactions, as immunocompromised status dramatically increases complication risk 1

Expected Outcomes

With appropriate management, cure rates are high:

• Approximately 91% of patients with BCG infection achieve cure with appropriate anti-tuberculous therapy 3
• However, quality of life can be significantly impaired during the prolonged treatment course 2
• Mortality from disseminated BCG disease occurs at 0.06-1.56 cases per million doses, primarily in immunocompromised persons 1