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Forrest Classification

Forrest Classification: Endoscopic assessment of peptic ulcer bleeding. Predicts rebleeding risk and guides therapeutic intervention.

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Endoscopic assessment of peptic ulcers presenting with acute gastrointestinal bleeding

To guide the decision for endoscopic haemostasis (thermal, clips, or injectables)

To predict the risk of re-bleeding and associated mortality

To assist in triage decisions (ICU vs. ward monitored discharge)

Timing of Endoscopy

Clinical guidelines (ACG/ESGE) recommend performing endoscopy within 24 hours of presentation. In high-risk patients (haemodynamic instability), earlier endoscopy (< 12 hours) should be considered after resuscitation.

Section 2

Formula & Logic

The 6 Categories

Grade Ia: Spurting haemorrhage (Active arterial bleed).

Grade Ib: Oozing haemorrhage (Active non-spurting/venous-like).

Grade IIa: Visible non-bleeding vessel (High risk for re-bleed).

Grade IIb: Adherent clot (Cannot be washed away; obscures vessel).

Grade IIc: Haematin-covered flat spot (Low risk).

Grade III: Clean based ulcer (Minimal risk).

Risk of Re-bleeding without Therapy

Forrest Ia/Ib	55–90% risk of recurrence
Forrest IIa	43–55% risk of recurrence
Forrest IIb	22–33% risk of recurrence
Forrest IIc/III	< 5% risk of recurrence

Section 3

Pearls/Pitfalls

Mandatory Endoscopic Therapy

All Forest Ia, Ib, and IIa ulcers REQUIRE endoscopic intervention (Dual-modality: e.g., Epinephrine injection + Clips or Thermal cautery). Therapeutic intervention for IIb (adherent clot) is debated but often performed after removing the clot to expose the underlying vessel.

Early Discharge Candidate

A Forrest III (clean base) ulcer in a clinically stable patient with a low Glasgow-Blatchford Score (< 2) is a candidate for early discharge and outpatient management.

Clinical Pearls

Forrest IIa (visible vessel) is the most "dangerous" subtle finding; it carries a massive re-bleed risk even if not actively bleeding at the moment of inspection

PPI "Bolus and Drip" (80mg + 8mg/hr) is indicated for Forrest Ia, Ib, IIa, and IIb to maximize stable clot formation

Re-inspection endoscopy is not routinely indicated unless clinical evidence of re-bleeding occurs

Section 4

Next Steps

Management Pathways

Class I - IIa: Admit (72-hour observation); IV PPI; Liquid to regular diet as tolerated after 24h stability.

Class IIc - III: Step-down care; Oral PPI; Early discharge consideration.

Complementary Scoring

Glasgow-Blatchford Score (Pre-endoscopy)

Rockall Score (Post-endoscopy)

AIMS65 Score (Mortality)

Section 5

Evidence Appraisal

Foundational Classification

Endoscopy in gastrointestinal bleeding.

Forrest JA et al. • Lancet. 1974;2(7877):394-7. The foundational paper establishing the nomenclature.

View Source

Consensus Guidelines

Management of patients with ulcer bleeding.

Laine L et al. • American Journal of Gastroenterology. 2012;107(3):345-60. ACG guideline formalizing the role of Forrest-driven therapy.

View Source

Section 6

Literature

The Forrest System

Developed by J.A. Forrest in 1974 at the Royal Infirmary of Edinburgh. It provided the first reproducible language for endoscopists to communicate the "activity" of an ulcer. Before this, terms like "bleeding ulcer" were generic and failed to predict which patients were actually at high risk of rapid exsanguination.

Last Comprehensive Review: 2026

Related Gastroenterology Tools

Glasgow-Blatchford Score

Harvey-Bradshaw Index

Crohn's Disease Activity Index

Mayo Score

Truelove & Witts Criteria

Adenoma Detection Rate

Have feedback about this calculator?Let us know.

Forrest Classification

Forrest Classification: Endoscopic assessment of peptic ulcer bleeding. Predicts rebleeding risk and guides therapeutic intervention.

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Endoscopic assessment of peptic ulcers presenting with acute gastrointestinal bleeding

To guide the decision for endoscopic haemostasis (thermal, clips, or injectables)

To predict the risk of re-bleeding and associated mortality

To assist in triage decisions (ICU vs. ward monitored discharge)

Timing of Endoscopy

Section 2

Formula & Logic

The 6 Categories

Grade Ia: Spurting haemorrhage (Active arterial bleed).

Grade Ib: Oozing haemorrhage (Active non-spurting/venous-like).

Grade IIa: Visible non-bleeding vessel (High risk for re-bleed).

Grade IIb: Adherent clot (Cannot be washed away; obscures vessel).

Grade IIc: Haematin-covered flat spot (Low risk).

Grade III: Clean based ulcer (Minimal risk).

Risk of Re-bleeding without Therapy

Forrest Ia/Ib	55–90% risk of recurrence
Forrest IIa	43–55% risk of recurrence
Forrest IIb	22–33% risk of recurrence
Forrest IIc/III	< 5% risk of recurrence

Section 3

Pearls/Pitfalls

Mandatory Endoscopic Therapy

Early Discharge Candidate

A Forrest III (clean base) ulcer in a clinically stable patient with a low Glasgow-Blatchford Score (< 2) is a candidate for early discharge and outpatient management.

Clinical Pearls

Forrest IIa (visible vessel) is the most "dangerous" subtle finding; it carries a massive re-bleed risk even if not actively bleeding at the moment of inspection

PPI "Bolus and Drip" (80mg + 8mg/hr) is indicated for Forrest Ia, Ib, IIa, and IIb to maximize stable clot formation

Re-inspection endoscopy is not routinely indicated unless clinical evidence of re-bleeding occurs

Section 4

Next Steps

Management Pathways

Class I - IIa: Admit (72-hour observation); IV PPI; Liquid to regular diet as tolerated after 24h stability.

Class IIc - III: Step-down care; Oral PPI; Early discharge consideration.

Complementary Scoring

Glasgow-Blatchford Score (Pre-endoscopy)

Rockall Score (Post-endoscopy)

AIMS65 Score (Mortality)

Section 5

Evidence Appraisal

Foundational Classification

Endoscopy in gastrointestinal bleeding.

Forrest JA et al. • Lancet. 1974;2(7877):394-7. The foundational paper establishing the nomenclature.

View Source

Consensus Guidelines

Management of patients with ulcer bleeding.

Laine L et al. • American Journal of Gastroenterology. 2012;107(3):345-60. ACG guideline formalizing the role of Forrest-driven therapy.

View Source

Section 6

Literature

The Forrest System

Last Comprehensive Review: 2026

Related Gastroenterology Tools

Glasgow-Blatchford Score

Harvey-Bradshaw Index

Crohn's Disease Activity Index

Mayo Score

Truelove & Witts Criteria

Adenoma Detection Rate

Have feedback about this calculator?Let us know.

Forrest Classification

Spurting Hemorrhage

Oozing Hemorrhage

Visible Vessel (Non-bleeding)

Adherent Clot

Pigmented Flat Spot

Clean Ulcer Base

Clinical Details

When to Use

When to Use

Timing of Endoscopy

Formula & Logic

The 6 Categories

Risk of Re-bleeding without Therapy

Pearls/Pitfalls

Mandatory Endoscopic Therapy

Early Discharge Candidate

Clinical Pearls

Next Steps

Management Pathways

Complementary Scoring

Evidence Appraisal

Foundational Classification

Endoscopy in gastrointestinal bleeding.

Consensus Guidelines

Management of patients with ulcer bleeding.

Literature

The Forrest System

Related Gastroenterology Tools

Forrest Classification

Spurting Hemorrhage

Oozing Hemorrhage

Visible Vessel (Non-bleeding)

Adherent Clot

Pigmented Flat Spot

Clean Ulcer Base

Clinical Details

When to Use

When to Use

Timing of Endoscopy

Formula & Logic

The 6 Categories

Risk of Re-bleeding without Therapy

Pearls/Pitfalls

Mandatory Endoscopic Therapy

Early Discharge Candidate

Clinical Pearls

Next Steps

Management Pathways

Complementary Scoring

Evidence Appraisal

Foundational Classification

Endoscopy in gastrointestinal bleeding.

Consensus Guidelines

Management of patients with ulcer bleeding.

Literature

The Forrest System

Related Gastroenterology Tools