Developer site: The content shown here is test data.

MyEClinic
MyEClinic
Health Dictionary AI Health Chat Find an Online Doctor
A serene Zen garden with raked sand and smooth stones, symbolising clarity and calm

Health Dictionary

Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.

Back to skin conditions

Ulcerative colitis classification

Introduction

Overview

Overview

Ulcerative colitis (UC) is classified along two complementary axes that together drive treatment selection: anatomic extent, described by the Montreal classification as proctitis (E1), left-sided colitis (E2), or extensive colitis (E3), and disease activity/severity.[1][2] Current definitions of severity integrate patient-reported outcomes, endoscopic scores (Mayo Endoscopic Score or UCEIS), biomarkers, disease course, and disease impact, rather than symptoms alone.[1] Validated indices include the Truelove and Witts criteria, the Mayo Score and its modified versions, and endoscopic indices. In clinical practice, patients are grouped into three treatment-relevant tiers: mild to moderate, moderate to severe, and acute severe ulcerative colitis (ASUC). ASUC has replaced the older term “fulminant colitis”.[2][3]

Classification

Classification

Classification by Anatomic Extent (Montreal Classification)

The Montreal classification is the standard system for describing colonic involvement in UC and is used by both ACG and AGA guidance.[1][4][2]

Montreal classification of ulcerative colitis extent
Category Montreal code Extent Approximate frequency at diagnosis
Ulcerative proctitis E1 Limited to the rectum (distal to the rectosigmoid junction, within ~18 cm of the anal verge) ~29%[1][2]
Left-sided (distal) colitis E2 Extends proximally from the rectum up to the splenic flexure ~40%[1][2]
Extensive colitis / pancolitis E3 Extends proximal to the splenic flexure, up to the entire colorectum ~31%[1][2]
  • Extent determines whether topical, oral, or combined therapy is appropriate, and it correlates with prognosis.[2]
  • Extent is dynamic. Up to ~30% of patients progress to more extensive disease within 10 years, so extent should be reassessed periodically.[2]
  • Although extent broadly affects prognosis, current ACG guidance states that extent alone should not limit therapeutic options. A patient with limited disease may still have severe, refractory disease that requires advanced therapy.[1][4]

Classification by Disease Activity and Severity

Severity is no longer a single symptom-based number. The 2025 ACG update defines it as a composite of four domains:[1]

  • Patient-reported outcomes (PROs): rectal bleeding, stool frequency, and bowel urgency. Urgency is now validated as a distinct PRO and is among the most bothersome symptoms reported by patients.
  • Inflammatory burden: endoscopic extent and severity, plus fecal calprotectin, C-reactive protein (CRP), and serum albumin.
  • Disease course: hospitalizations, corticosteroid requirement, and prior medication failure.
  • Disease impact: health-related quality of life and social functioning.

The field distinguishes disease activity from disease severity. Activity is a cross-sectional measure of current symptomatic and endoscopic inflammation. Severity is a longitudinal measure of cumulative disease burden and risk of complications.[5]

Validated Activity and Severity Indices

Index Components / thresholds Clinical use and limitations
Truelove and Witts criteria (1955) Clinical and laboratory parameters (bloody stool frequency, heart rate, temperature, hemoglobin, ESR) The original clinical index. It is now used mainly to define ASUC and the need for hospitalization. It gives no quantitative or longitudinal measure and omits urgency, nocturnal symptoms, extraintestinal manifestations, and endoscopy.[1][4]
Mayo Score (Disease Activity Index) Range 0–12. Four subscores (stool frequency, rectal bleeding, physician global assessment, endoscopy), each scored 0–3. The most widely used index in practice and trials.[6][1]
Modified Mayo Score and PRO2 The Modified Mayo Score excludes the subjective physician global assessment. PRO2 combines stool frequency and rectal bleeding. Both are now standard clinical trial endpoints.[6][1]
Mayo Endoscopic Score (MES) and UC Endoscopic Index of Severity (UCEIS) MES 0–1 defines endoscopic remission and MES 2–3 defines endoscopic activity. Ulcers and/or spontaneous bleeding define severe endoscopic activity. ACG recommends using a validated endoscopic index to report endoscopic severity and to define treatment targets.[1][7]
Composite / burden tools The DUBLIN score (MES × Montreal extent) and the multidimensional Disease Severity Index, which integrate inflammatory burden, complications, treatment intensity, and disease impact. These capture cumulative burden beyond cross-sectional activity. They are used mainly in research and specialist settings.[5][7]
Interpretation of the total Mayo Score
Total Mayo Score Activity category
0–2, with no subscore >1 Remission
3–5 Mild
6–10 Moderate to severe
11–12 Severe

In AGA guidance and clinical trials, moderate to severe UC is generally defined as a Mayo Score of 6–12 with an endoscopic subscore of 2 or 3.[6][3]

Severity Tiers in Clinical Practice

Contemporary guidelines group adult UC into three treatment-relevant tiers.[2][8][3]

Tier Representative definition Management implication
Mild to moderate Fewer than 4–6 bowel movements/day, mild to moderate rectal bleeding, no constitutional symptoms, and low overall inflammatory burden[8] 5-aminosalicylates (oral and/or rectal, selected by extent) are first-line therapy.[8][2]
Moderate to severe Frequent bloody stools with urgency, elevated inflammatory markers, and Mayo Score 6–12 with endoscopic subscore 2–3[3][9]
 Corticosteroids for induction only, as a bridge to biologics or oral small molecules for maintenance.[2][3]
Acute severe UC (ASUC) (modified Truelove–Witts criteria) ≥6 bloody stools/day plus ≥1 sign of systemic toxicity: heart rate >90 beats/min, temperature >37.8°C, hemoglobin <10.5 g/dL, or ESR >30 mm/h[2][3] Hospitalization and IV corticosteroids. Rescue infliximab or cyclosporine if refractory to IV steroids.[3][9]
  • ASUC is a medical emergency. Short-term colectomy risk is ~25–30% in hospitalized patients.[3]
  • Before assigning severity or escalating therapy, exclude infectious mimics, particularly Clostridioides difficile and cytomegalovirus (CMV).
    C. difficile is found in ~3% of ASUC cases, and ACG strongly recommends testing all hospitalized patients.[1][2]
  • Document objective inflammation (fecal calprotectin, CRP, endoscopy, or imaging) before attributing symptoms to active UC and starting corticosteroids.[10]
  • Certain features predict an aggressive course and colectomy at any severity tier. They warrant earlier treatment intensification:[8][3]
    • Age <40 years at diagnosis
    • Extensive colitis
    • Severe endoscopic disease (large or deep ulcers)
    • Prior hospitalization
    • Elevated CRP or low albumin

Clinical Pearls and Common Pitfalls

  • In every UC assessment, record Montreal extent (E1–E3) together with a validated clinical index (Mayo or Modified Mayo) and an endoscopic index (MES or UCEIS). This anchors therapy selection and allows longitudinal comparison.[1]
  • Endoscopic remission (MES 0–1) is a treatment target beyond symptom control.[1]
  • Avoid classifying severity on symptoms alone. Doing so can miss objective inflammation, or can overcall severity when IBS-type symptoms occur without active disease.[10]
  • Use the defined ASUC criteria rather than the obsolete term “fulminant colitis”.[2][3]
  • Do not let limited extent restrict therapy. Severe, refractory proctitis may still require advanced therapy.[1]
References

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 Rubin DT, Ananthakrishnan AN, Siegel CA, Barnes EL, Long MD (2025). “ACG Clinical Guideline Update: Ulcerative Colitis in Adults”. Am J Gastroenterol. 120 (6): 1187–1224. doi:10.14309/ajg.0000000000003463. PMID 40701556 Check |pmid= value (help).
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 Gros B, Kaplan GG (2023). “Ulcerative Colitis in Adults: A Review”. JAMA. 330 (10): 951–965. doi:10.1001/jama.2023.15389. PMID 37698559 Check |pmid= value (help).
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 Feuerstein JD, Isaacs KL, Schneider Y, Siddique SM, Falck-Ytter Y, Singh S (2020). “AGA Clinical Practice Guidelines on the Management of Moderate to Severe Ulcerative Colitis”. Gastroenterology. 158 (5): 1450–1461. doi:10.1053/j.gastro.2020.01.006. PMC 7175923 Check |pmc= value (help). PMID 31945371.
  4. ↑ 4.0 4.1 4.2 Rubin DT, Ananthakrishnan AN, Siegel CA, Sauer BG, Long MD (2019). “ACG Clinical Guideline: Ulcerative Colitis in Adults”. Am J Gastroenterol. 114 (3): 384–413. doi:10.14309/ajg.0000000000000152. PMID 30840605.
  5. ↑ 5.0 5.1 Swaminathan A, Day AS, Sparrow MP, Peyrin-Biroulet L, Siegel CA, Gearry RB (2024). “Review article: Measuring disease severity in inflammatory bowel disease – Beyond treat to target”. Aliment Pharmacol Ther. 60 (9): 1176–1199. doi:10.1111/apt.18231.
  6. ↑ 6.0 6.1 6.2 Kobayashi T, Siegmund B, Le Berre C, Wei SC, Ferrante M, Shen B, Bernstein CN, Danese S, Peyrin-Biroulet L, Hibi T (2020). “Ulcerative colitis”. Nat Rev Dis Primers. 6 (1): 74. doi:10.1038/s41572-020-0205-x.
  7. ↑ 7.0 7.1 Chen H, Lin X, Pan X, Xu H, Zhang X, Liang G; et al. (2023). “Development and validation of a blood routine-based extent and severity clinical decision support tool for ulcerative colitis”. Sci Rep. 13 (1): 21368. doi:10.1038/s41598-023-48569-5. PMC 10696009 Check |pmc= value (help). PMID 38049548 Check |pmid= value (help).
  8. ↑ 8.0 8.1 8.2 8.3 Ko CW, Singh S, Feuerstein JD, Falck-Ytter C, Falck-Ytter Y, Cross RK (2019). “AGA Clinical Practice Guidelines on the Management of Mild-to-Moderate Ulcerative Colitis”. Gastroenterology. 156 (3): 748–764. doi:10.1053/j.gastro.2018.12.009.
  9. ↑ 9.0 9.1 Loeb LP, Davis AM, Kinnucan JA (2026). “Ulcerative Colitis Management in Adults”. JAMA. doi:10.1001/jama.2026.8803.
  10. ↑ 10.0 10.1 Feuerstein JD, Rubin DT, Aberra FN, Yarur AJ, Malter L (2025). “Appropriate Use and Complications of Corticosteroids in Inflammatory Bowel Disease: A Comprehensive Review”. Clin Gastroenterol Hepatol. 23 (12): 2068–2082. doi:10.1016/j.cgh.2025.05.019. PMID 40588110 Check |pmid= value (help).

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Fahad Hasan, M.D.[2] Usama Talib, BSc, MD [3]