Single Best Answer (SBA) · Crohn's Disease and Ulcerative Colitis
A 30-year-old man with IBD develops episodes of intestinal obstruction, an enterovesical fistula causing recurrent urinary tract infections, and perianal fissures. These complications most strongly favour which diagnosis?
Show answer and explanation
Answer: A. Crohn's disease
Transmural complications point to Crohn's disease
Intestinal obstruction, fistulae (e.g. enterovesical causing recurrent UTIs) and perianal disease all arise from the transmural inflammation of Crohn's disease.
Why these favour CD over UC
| Feature | Crohn's | UC |
|---|---|---|
| Depth of inflammation | Transmural | Mucosa/submucosa |
| Strictures/obstruction | Common (transmural fibrosis) | Rare |
| Fistulae | Common (entero-enteric, enterovesical, enterovaginal, enterocutaneous) | Rare |
| Perianal disease | Common (fissures, fistulae, abscesses) | Usually spared |
The mechanism
- Full-thickness inflammation lets the disease penetrate the bowel wall to form fistulae and strictures, and involve the perianal region.
- UC, being superficial and mucosal, rarely causes obstruction or fistulae.
Clinical clue
An enterovesical fistula presents with recurrent UTIs (and sometimes pneumaturia/faecaluria) - a Crohn's complication.
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