Does Plaquenil (hydroxychloroquine) affect the yield of colonoscopy for Crohn's disease?

Impact of Plaquenil (Hydroxychloroquine) on Colonoscopy Yield for Crohn's Disease

There is no evidence that Plaquenil (hydroxychloroquine) decreases the yield of colonoscopy for Crohn's disease diagnosis or monitoring.

Diagnostic Approach for Crohn's Disease

Ileocolonoscopy remains the gold standard first-line investigation for suspected Crohn's disease, regardless of whether a patient is taking hydroxychloroquine:

• Ileocolonoscopy with biopsies is the initial diagnostic procedure of choice for suspected Crohn's disease 1, 2
• It allows for direct visualization of the colon and terminal ileum with histological confirmation
• Diagnostic accuracy of colonoscopy for differentiating between Crohn's disease and ulcerative colitis is approximately 89% 3

Key Endoscopic Features for Crohn's Disease Diagnosis

When performing colonoscopy, the following features are most suggestive of Crohn's disease:

• Discontinuous involvement (skip lesions)
• Anal lesions
• Cobblestoning of mucosa
• Deep ulcerations
• Strictures 1, 3

Limitations of Colonoscopy and Complementary Diagnostic Methods

While ileocolonoscopy is essential, it has limitations that should be addressed regardless of hydroxychloroquine use:

• Terminal ileum intubation may not always be successful
• Cannot visualize proximal small bowel beyond the reach of the colonoscope
• Up to 20% of patients have isolated proximal small bowel disease that would be missed by ileocolonoscopy alone 2

Complementary Diagnostic Methods

For complete evaluation, additional diagnostic methods should be considered:

1. MR Enterography: Preferred first-line cross-sectional imaging, especially in younger patients to avoid radiation exposure 1, 2

2. Small Bowel Capsule Endoscopy (SBCE):

   • Recommended when small bowel Crohn's disease is suspected despite normal or inconclusive ileocolonoscopy and cross-sectional imaging 1
   • Has higher diagnostic yield for small bowel lesions compared to ileocolonoscopy 1
   • A patency capsule should be used prior to SBCE in patients with obstructive symptoms 1

3. CT Enterography: May be used in acutely symptomatic patients, older patients, or when rapid diagnosis is needed 2

Considerations for Drug-Induced Lesions

When evaluating endoscopic findings in patients taking hydroxychloroquine:

• Non-steroidal anti-inflammatory drugs (NSAIDs) are known to cause small bowel lesions that can mimic Crohn's disease and should be withdrawn at least four weeks prior to small bowel capsule endoscopy 1
• However, there is no specific evidence that hydroxychloroquine causes similar lesions or affects the diagnostic yield of colonoscopy

Monitoring Disease Activity

For monitoring disease activity in established Crohn's disease:

• Ileocolonoscopy remains important for assessing mucosal healing, which is associated with better outcomes 1
• Patients who achieve complete mucosal healing have fewer disease-related hospitalizations (42.2% vs. 59.3%) and lower need for major abdominal surgery (14.1% vs. 38.4%) 1
• Faecal calprotectin can be used as a non-invasive marker to monitor disease activity between endoscopic evaluations 1

Conclusion

Based on current evidence, hydroxychloroquine does not appear to decrease the diagnostic yield of colonoscopy for Crohn's disease. The standard diagnostic approach using ileocolonoscopy with biopsies, complemented by cross-sectional imaging and/or small bowel capsule endoscopy when appropriate, should be followed regardless of hydroxychloroquine use.