Clues Pointing TO This Diagnosis

Young adult — classic age of onset — 15 to 35
Bloody diarrhea — hallmark symptom — always present in UC
Mucus in stool
Frequent bowel movements — urgency — tenesmus
Cramping abdominal pain
Extraintestinal manifestations — joint pain — eye inflammation
Weight loss — malnutrition
Continuous inflammation from rectum — always involves rectum — spreads proximally
Crypt abscesses on biopsy — superficial mucosal inflammation only
Responds to aminosalicylates — corticosteroids — biologics

Why It's NOT the Similar Diseases

NOT Crohn's disease — Crohn's can affect ANY part of GI tract — transmural inflammation — skip lesions — can cause fistulas — strictures — abscesses. UC is LIMITED to colon — ALWAYS starts at rectum — CONTINUOUS inflammation — SUPERFICIAL mucosal involvement — NO fistulas.
NOT infectious colitis — C. diff — Salmonella — Shigella — causes acute bloody diarrhea but typically resolves — fever — recent antibiotic use — travel history. Natalie's symptoms lasted three months — stool cultures and C. diff testing rule these out.
NOT irritable bowel syndrome — IBS causes cramping — diarrhea — but NO blood — NO weight loss — NO inflammation on scope. Normal colonoscopy in IBS.
NOT colon cancer — typically in older patients — focal mass on scope — not continuous diffuse mucosal inflammation in a 26-year-old.
NOT ischemic colitis — occurs in older patients with vascular disease — affects watershed areas — not the continuous rectal-to-proximal pattern of UC.

Differential Diagnosis List

Crohn's disease — ruled out by continuous rectal involvement — superficial mucosal inflammation — no skip lesions — no fistulas
Infectious colitis — ruled out by three month duration — negative stool cultures — negative C. diff
IBS — ruled out by bloody stool — weight loss — active inflammation on scope
Colon cancer — ruled out by age — diffuse mucosal inflammation not mass
Ischemic colitis — ruled out by age — continuous rectal pattern

Key Distinguishing Test

Colonoscopy with biopsy — gold standard — shows continuous mucosal inflammation from rectum — crypt abscesses — goblet cell depletion. Stool cultures and C. diff testing — rule out infectious cause. Inflammatory markers — CRP — ESR — fecal calprotectin. CT enterography — if Crohn's suspected to evaluate small bowel.

Board Note

📝 UC VERSUS CROHN'S — KEY DISTINCTIONS: UC — limited to colon — always involves rectum — continuous inflammation — superficial mucosal — bloody diarrhea hallmark — no fistulas — smoking is protective. Crohn's — anywhere mouth to anus — skip lesions — transmural — fistulas — strictures — abscesses — smoking worsens. Both have extraintestinal manifestations. UC has higher risk of colorectal cancer — surveillance colonoscopy after 8 years of extensive colitis. Toxic megacolon — colon dilation above 6cm with systemic toxicity — can complicate both — surgical emergency.

“Natalie’s Story”