Can Crohn's disease (CD) change its area of involvement in the gastrointestinal (GI) tract in an adult patient with a history of CD initially affecting the sigmoid colon, who now presents with resolved colonoscopic abnormalities in that area but persistent diarrhea?

Can Crohn's Disease Change Location in the GI Tract?

Yes, Crohn's disease can change its area of involvement in the gastrointestinal tract over time, and the diagnosis may even be revised in a small percentage of cases. In your patient with resolved sigmoid abnormalities but persistent diarrhea, you must investigate for disease extension to other GI segments, particularly the small bowel and upper GI tract.

Evidence for Disease Location Changes

The diagnosis of IBD can evolve over time. 1 Endoscopy combined with other diagnostic modalities can differentiate CD from UC in 85% of patients, but importantly, the diagnosis may change over time. 1 In a prospective study of over 350 patients with IBD followed for more than 22 months, the IBD diagnosis was revised in 4% of cases. 1

Why Your Patient Needs Further Evaluation

Your patient's persistent diarrhea despite resolved sigmoid findings demands investigation for:

1. Small Bowel Disease (Most Likely)

• CD can affect any portion of the GI tract, with the small bowel alone affected in about one-third of patients, the colon alone in a somewhat higher percentage, and combined involvement in less than one-third. 2
• The inflammation in CD is characterized by discontinuous or "skip" lesions that can occur anywhere in the gastrointestinal tract. 2
• Order MR enterography or CT enterography to assess for small bowel involvement, strictures, and complications. 3

2. Upper GI Tract Involvement

• Upper GI endoscopic lesions suggestive of Crohn's disease include focally active gastritis in the absence of Helicobacter pylori. 1
• With radiological double-contrast technique, early signs of upper gastrointestinal CD may be detected in 20-40% of patients with ileocolitis. 4
• When CD involves the upper GI tract, there is nearly always concomitant disease in the small bowel or colon. 4

3. Post-Operative or Post-Treatment Recurrence Pattern

• In the natural history of CD, endoscopic recurrence precedes the development of clinical symptoms. 1
• Endoscopic recurrence can occur in 30-90% of patients at different locations within 12 months and almost universally by 5 years. 5

Recommended Diagnostic Algorithm

Immediate Workup:

1. Complete ileocolonoscopy with multiple biopsies from at least six segments, taking a minimum of two biopsies per site, documenting lesion distribution and presence of skip lesions. 3

2. Cross-sectional imaging (MR or CT enterography) to evaluate the entire small bowel for active disease, strictures, or penetrating complications. 3

3. Fecal calprotectin - if >100 μg/g, this supports active IBD with 93% sensitivity and 96% specificity. 3

4. Laboratory assessment: CBC, CRP, albumin, liver function, iron studies to assess disease activity and nutritional status. 3

If Initial Evaluation is Negative:

1. Upper GI endoscopy with esophageal, gastric, and duodenal biopsies to identify focal inflammation or granulomas, particularly if symptoms persist. 3

2. Rule out infectious causes: Stool cultures for Salmonella, Shigella, Campylobacter, and C. difficile toxin assay. 3 Recent studies show 18.1% of CD patients may have concurrent infections. 1

Common Pitfalls to Avoid

• Don't assume resolved colonoscopic findings mean disease remission - CD is transmural and may have active disease beyond mucosal visualization. 2
• Don't overlook small bowel disease - it's present in approximately 80% of CD patients (either alone or combined with colonic disease). 2, 5
• Don't forget that uneven distribution of inflammation can occur in patients with long-standing disease or after treatment. 1
• Rectal sparing occurs in >3% of UC patients, so the absence of rectal disease doesn't definitively indicate CD over UC. 1

Clinical Implications

The transmural nature of CD inflammation explains why mucosal healing on colonoscopy doesn't always correlate with symptom resolution - there may be:

• Active inflammation in other GI segments 2
• Strictures causing partial obstruction 2
• Bacterial overgrowth from structural changes 5
• Bile acid malabsorption from ileal disease 5

Your patient requires comprehensive re-evaluation of the entire GI tract, not just repeat colonoscopy of the previously affected sigmoid colon, to identify the current site(s) of active disease causing persistent diarrhea.