ACG Clinical Guideline 2025
Dr. David Rubin
IBD
Ulcerative Colitis in Adults
Diagnosis, induction therapy, maintenance, and management of acute severe UC — ACG 2025 Guidelines.
Diagnosis & Severity
Clinical, endoscopic & histologic assessment
UC: Diagnosis and Severity Classification
UC is a chronic mucosal inflammatory disease of the colon, beginning at the rectum and extending proximally in a continuous pattern. Accurate severity assessment guides therapy.
| Severity | Stool Frequency | Rectal Bleeding | Systemic Features |
|---|---|---|---|
| Mild | <4/day | Intermittent | None; normal ESR/CRP |
| Moderate | 4–6/day | Frequent | Mild anemia, elevated CRP |
| Severe (ASUC) | >6/day | Continuous | Fever, tachycardia, anemia, CRP >30 |
| Fulminant | >10/day | Continuous + blood | Toxic megacolon, peritoneal signs |
Endoscopic Severity (Mayo Score)
Mayo 0Normal
Mayo 1Mild — erythema, decreased vascular pattern
Mayo 2Moderate — marked erythema, absent vascular pattern, erosions
Mayo 3Severe — spontaneous bleeding, ulceration
Key Diagnostic Tests
Ileocolonoscopy with biopsies — gold standard
Fecal calprotectin — disease activity monitoring
Stool cultures (rule out infectious colitis)
ANCA, ASCA (limited utility in established disease)
Cross-sectional imaging if deep disease suspected
Rubin DT et al. ACG Clinical Guideline: Ulcerative Colitis in Adults. Am J Gastroenterol. 2025.