What is the next step in outpatient GI workup for a patient with erosive chronic ileitis, persistent diarrhea, and weight loss, with the last colonoscopy (colo) performed in 2023?

Next Steps in GI Workup for Erosive Chronic Ileitis with Persistent Diarrhea and Weight Loss

The next step in outpatient GI workup for this patient with erosive chronic ileitis, persistent diarrhea, and weight loss should be a comprehensive evaluation for inflammatory bowel disease (IBD), specifically Crohn's disease, including serological markers, fecal calprotectin, and small bowel imaging.

Initial Assessment of Alarm Features

This patient presents with several concerning features that require thorough investigation:

• Erosive chronic ileitis (already documented)
• Persistent diarrhea
• Weight loss
• Recent colonoscopy (2023)

These symptoms represent "red flags" that warrant further evaluation beyond functional disorders 1. The combination of weight loss and diarrhea with documented ileitis strongly suggests an organic rather than functional etiology.

Diagnostic Approach

1. Laboratory Testing

• Complete blood count - to assess for anemia, which is common in IBD
• Inflammatory markers - C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)
• Serum albumin - to assess nutritional status and disease severity
• Fecal calprotectin - highly sensitive marker for intestinal inflammation 1
  • Using a cutoff of >50 mg/g has good sensitivity for distinguishing IBD from IBS
• Serological markers - anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA)

2. Small Bowel Imaging

Since the patient has already had a colonoscopy in 2023 showing erosive chronic ileitis, the next step should include:

• MR enterography - gold standard for evaluating small bowel in suspected Crohn's disease
  • Allows assessment of disease extent, complications (strictures, fistulae), and activity
• CT enterography - alternative if MR is unavailable or contraindicated

3. Capsule Endoscopy

• Consider if small bowel imaging is negative but clinical suspicion for Crohn's disease remains high
• Contraindicated if strictures are present on imaging

4. Additional Testing to Consider

• Stool studies to exclude infectious causes:
  • Stool culture
  • Ova and parasites
  • Clostridioides difficile toxin
• Celiac disease testing - anti-tissue transglutaminase IgA and total IgA 1
• Bile acid malabsorption testing - SeHCAT scan or serum 7α-hydroxy-4-cholesten-3-one 1
  • Particularly relevant for patients with terminal ileal disease

Differential Diagnosis

The differential diagnosis for erosive chronic ileitis with diarrhea and weight loss includes:

1. Crohn's disease - most likely given the erosive ileitis 1
2. Infectious ileitis - bacterial (tuberculosis, Yersinia), parasitic (Giardia)
3. Medication-induced ileitis - NSAIDs, olmesartan 1
4. Ischemic ileitis - less common but possible 2
5. Celiac disease with erosive jejunoileitis - rare complication 3
6. Lymphoma - particularly in older patients or those with immune disorders 1

Management Considerations

The management will depend on the final diagnosis, but given the presence of erosive ileitis with persistent symptoms:

• If Crohn's disease is confirmed, treatment options include:

  • 5-ASA compounds for mild disease
  • Corticosteroids for moderate-severe disease
  • Immunomodulators (azathioprine, 6-mercaptopurine) for maintenance
  • Biologics (anti-TNF, anti-integrins, IL-12/23 inhibitors) for moderate-severe or refractory disease 1

• If other causes are identified, targeted therapy should be initiated

Conclusion

Given the documented erosive chronic ileitis with persistent diarrhea and weight loss, the most appropriate next step is a focused workup for inflammatory bowel disease, particularly Crohn's disease, with fecal calprotectin, inflammatory markers, and small bowel imaging. This approach will help determine the extent of disease and guide appropriate management.