In a 27-year-old man with suspected inflammatory bowel disease, which of the following statements is correct?

Answer: E is Correct

The correct answer is E: Unlike in ulcerative colitis, smoking increases the risk of Crohn's disease, its relapses, and treatment resistance. This statement is strongly supported by high-quality guideline evidence demonstrating the opposite effects of smoking on these two IBD subtypes 1.

Why E is Correct

Smoking has paradoxical and opposite effects on Crohn's disease versus ulcerative colitis:

Crohn's Disease and Smoking

• Cigarette smoking is MORE common in patients diagnosed with Crohn's disease (47% in those diagnosed over age 40 vs 27% in background population) 1
• Continued smoking results in a worse disease course compared to those who quit or never-smokers 1
• 2.5-fold increased risk of repeat surgery 1
• Twofold increased risk of clinical recurrence 1
• Higher risk of disease flare, higher incidence of surgery, and higher risk of postoperative recurrent disease 1
• Passive smoking and light smoking (<10 per day) are just as harmful as heavy smoking 1
• Adverse effects are more pronounced in women than men with Crohn's disease 1

Ulcerative Colitis and Smoking (The Opposite Effect)

• UC is more common in non-smokers and more likely to arise in those who recently quit smoking 1
• Highest risk period for UC onset is 2-5 years after stopping smoking 1
• UC patients who smoke have reduced colectomy rates, less primary sclerosing cholangitis, and less back-wash ileitis 1
• UC patients who quit smoking have a significantly worse disease course than those who continue 1

Why Other Options Are Incorrect

A) Crohn's disease typically affects the upper gastrointestinal tract - INCORRECT

• Crohn's disease can affect any part of the GI tract from mouth to anus, but most commonly affects the terminal ileum and colon, not typically the upper GI tract 2, 3

B) Rectal involvement is found only in ulcerative colitis - INCORRECT

• While UC characteristically involves the rectum with continuous inflammation, Crohn's disease can also involve the rectum, though it typically shows rectal sparing 3
• Crohn's colitis can present with perianal disease and rectal involvement 2

C) Ulcerative colitis causes transmural bowel involvement - INCORRECT

• This is backwards: Crohn's disease causes transmural inflammation 4
• Ulcerative colitis causes superficial mucosal inflammation limited to the mucosa and submucosa 5

D) The first-line diagnostic test is abdominal CT scanning - INCORRECT

• Ileocolonoscopy with biopsies is the cornerstone diagnostic tool and first-line examination 3
• Endoscopy with histology is required for diagnosis 5
• Imaging (CT enterography, MRE, or intestinal ultrasound) is used as a complementary first-line examination alongside colonoscopy, not as the primary diagnostic test 3

Clinical Implications for This Patient

Given this 27-year-old man's presentation with bloody diarrhea, tenesmus, and elevated inflammatory markers:

1. Smoking history is critical - Ask specifically about smoking status as it helps differentiate between CD and UC and has major prognostic implications
2. If he has Crohn's disease and smokes: Strongly counsel smoking cessation with referral to smoking cessation services (behavioral therapy + pharmacotherapy) 1
3. If he has ulcerative colitis: Understand that smoking cessation may temporarily worsen symptoms, though long-term health benefits still outweigh risks
4. Diagnostic workup should include ileocolonoscopy with biopsies (not CT as first-line) plus imaging evaluation 3