What is the treatment for terminal ileitis on CT scan with a positive Quantiferon (Interferon-Gamma Release Assay) test?

Treatment of Terminal Ileitis with Positive Quantiferon Test

For terminal ileitis with a positive Quantiferon test, treatment should include a complete therapeutic regimen for latent tuberculosis infection (LTBI) with isoniazid for 9 months, followed by appropriate management of the underlying inflammatory bowel condition. 1

Diagnostic Considerations

Terminal ileitis with a positive Quantiferon test requires careful evaluation to determine the underlying cause, as several conditions can present with similar findings:

• Tuberculosis (TB): A positive Quantiferon test indicates LTBI or active TB infection
• Crohn's Disease: Common cause of terminal ileitis
• Other causes: NSAID-induced enteropathy, infectious ileitis, lymphoma, vasculitis, or neuroendocrine tumors 2, 3, 4

Diagnostic Approach:

1. Rule out active TB with chest X-ray and clinical evaluation
2. Consider CT enterography or MRI to better characterize the terminal ileitis
3. Consider colonoscopy with ileal biopsies if not already performed
4. Evaluate for other infectious causes with stool studies

Treatment Algorithm

Step 1: Treat Latent TB Infection

• First-line regimen: Isoniazid 300 mg daily (5 mg/kg maximum) for 9 months with vitamin B6 supplementation 1
• Alternative regimens:
  • Rifampicin 600 mg daily (10 mg/kg maximum) for 4 months
  • Rifapentine 900 mg plus isoniazid 900 mg once weekly for 12 doses (3 months) 1

Step 2: Manage Terminal Ileitis Based on Etiology

• If Crohn's Disease is confirmed:

  • For mild-moderate disease: Budesonide 9 mg daily for isolated ileo-cecal disease 5
  • For moderate-severe disease: Oral prednisolone 40 mg daily with gradual taper over 8 weeks 5
  • Maintenance therapy: Consider mesalazine for isolated ileal disease 1

• If TB ileitis is confirmed:

  • Full anti-TB regimen with isoniazid, rifampicin, ethambutol, and pyrazinamide for 2 months, followed by isoniazid and rifampicin for 4 months
  • If rifampicin hypersensitivity occurs (rare but serious), alternative regimens must be used 6

Important Considerations

Timing of Treatments

• When both LTBI and active IBD are present, biologic or small-molecule therapy should be delayed for at least 4 weeks after starting TB chemoprophylaxis 1
• In cases of greater clinical urgency, specialist consultation is recommended

Monitoring

• Monitor liver function tests during isoniazid therapy, especially in patients with pre-existing liver disease 1
• Follow up with repeat imaging and/or endoscopy to assess treatment response

Pitfalls to Avoid

• Misdiagnosis: Terminal ileitis is not always Crohn's disease; thorough evaluation is essential 3
• Inadequate TB treatment: Incomplete treatment of LTBI can lead to reactivation, especially if immunosuppressive therapy is later initiated 1
• Drug interactions: Be aware of potential interactions between TB medications and IBD treatments
• Delayed diagnosis of rare causes: Consider uncommon etiologies like IgA vasculitis or neuroendocrine tumors if standard treatments fail 4, 7

The effectiveness of LTBI treatment is high, with 9 months of isoniazid providing approximately 90% protection against TB reactivation 1. Proper treatment of both the LTBI and the underlying cause of terminal ileitis is essential for optimal outcomes and prevention of complications.