Acute Lower GI Bleeding

1. Clinical Overview

Summary

Acute lower gastrointestinal bleeding (LGIB) is a medical emergency characterized by bleeding from the gastrointestinal tract distal to the ligament of Treitz, presenting as hematochezia (bright red or maroon blood per rectum). The condition affects approximately 20-30 per 100,000 people annually with overall mortality of 2-4%, rising to 10-15% in high-risk patients. [1,2] Most bleeds (70-80%) stop spontaneously, but those that continue require urgent intervention. [5] Modern management emphasizes risk stratification using the validated Oakland score, early colonoscopy within 24 hours for high-risk patients, and CT angiography for active bleeding when colonoscopy is not feasible. [3,4,23] The Birmingham Score (2021) and updated clinical predictive models (2024) further refine risk stratification with 94% accuracy for adverse outcomes at threshold scores. [23,24] Successful management requires rapid assessment, appropriate resuscitation, risk-stratified investigation timing, and definitive treatment through endoscopic, radiological, or surgical intervention.

Key Facts

• Definition: Bleeding from GI tract distal to ligament of Treitz (jejunum, ileum, colon, rectum, anus)
• Incidence: 20-30 per 100,000/year; ~100,000 hospitalizations annually in the United States [1]
• Mortality: 2-4% overall; 10-15% in high-risk patients [2]
• Spontaneous cessation: 70-80% of cases [5]
• Risk stratification: Oakland score ≥9 requires urgent (less than 24h) intervention; Birmingham score ≥7 predicts 94% adverse outcome probability [3,23]
• Key investigation: Colonoscopy (89-97% diagnostic yield); CT angiography if active bleeding (85-90% sensitivity) [4,6]
• First-line treatment: IV access, fluid resuscitation, blood transfusion if Hb less than 70 g/L (less than 80 if cardiac disease), urgent colonoscopy with endoscopic therapy

Clinical Pearls

"Hematochezia ≠ Always Lower GI" — Massive upper GI bleeding (10-15% of hematochezia) can present with bright red blood if rapid gut transit. Always consider upper GI source if hemodynamically unstable or elevated urea:creatinine ratio. [7]

"Oakland and Birmingham Scores guide safe discharge" — Oakland score less than 8 identifies 95% safe for outpatient management; Birmingham score ≥7 predicts 94% adverse outcome probability. Both validated in multiple international cohorts. [3,8,23]

"Most diverticular bleeds stop spontaneously" — 70-80% cease without intervention, but 20-30% rebleed within 4 years. Endoscopic therapy reduces rebleeding by 50%. [5,9,25]

"CT angiography before angioembolization improves outcomes" — CTA localizes bleeding in 85-90% of active bleeds, guiding selective embolization and reducing ischemic complications (3% vs. 15%). [6,10]

"Angiodysplasia treatment evolving" — Argon plasma coagulation achieves 70-85% long-term hemostasis. Octreotide shows 77% response rate for recurrent bleeding; recent meta-analyses support somatostatin analogues in refractory cases. [11,26,27]

Why This Matters Clinically

Acute lower GI bleeding accounts for over 100,000 annual U.S. hospitalizations with mortality lower than upper GI bleeding but significant in anticoagulated elderly patients. [3] The 2023 ACG guidelines emphasize risk stratification as critical—Oakland score and Birmingham score identify patients safe for early discharge versus requiring urgent intervention, with 95% sensitivity and 94% adverse outcome prediction respectively. [3,23,24] Early colonoscopy (less than 24h) in high-risk patients improves diagnostic yield and reduces length of stay. [4,12] Angiographic embolization avoids surgery in 60-80% of persistent bleeding cases but requires careful patient selection given 3-10% ischemia risk. [10,13] Understanding these evidence-based pathways is essential for emergency medicine, gastroenterology, and surgical trainees.

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2. Epidemiology

Incidence & Prevalence

• Overall incidence: 20-30 per 100,000 population per year [1]
• United States: ~100,000 hospitalizations annually
• United Kingdom: ~20,000-30,000 hospitalizations annually
• Trend: Increasing incidence (aging population, anticoagulant use, NSAID use) [14]
• Peak age: 70-80 years (median age 75 years)
• Gender distribution: Slight male predominance (55% vs. 45%)

Demographics

Risk Factors

Non-Modifiable:

• Age > 60 years (risk increases exponentially with each decade) [14]
• Male sex
• Previous lower GI bleeding (20-30% recurrence rate) [9]
• Chronic kidney disease (uremic platelet dysfunction)
• Cirrhosis/portal hypertension (rectal varices, coagulopathy)

Modifiable:

Common Causes

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3. Pathophysiology

The Bleeding Cascade

Step 1: Underlying Pathology

• Diverticula: Outpouchings of colon wall at sites of vasa recta penetration → asymmetric dome with vessel exposed at fundus → erosion into artery → arterial hemorrhage
• Angiodysplasia: Degenerative vascular ectasia → dilated, thin-walled submucosal vessels → spontaneous rupture or trauma during peristalsis
• Colitis: Inflammatory mediators → mucosal ulceration → exposure of submucosal vessels → venous or arterial bleeding
• Tumors: Neovascularization → fragile, disorganized vessels → spontaneous bleeding or ulceration

Step 2: Vessel Exposure or Rupture

• Diverticula: Erosion into vasa recta (arterial branches) → high-pressure arterial bleeding
• Angiodysplasia: Thin-walled vessels rupture under normal luminal pressure
• Colitis: Progressive mucosal erosion → exposure of submucosal vascular plexus
• Tumors: Tumor outgrows blood supply → central necrosis → bleeding

Step 3: Hemorrhage Patterns

• Arterial bleeding: Bright red, may be pulsatile, large volume (can lose liters rapidly)
• Venous bleeding: Darker (maroon), slower, more likely to self-tamponade
• Volume loss: 30% of blood volume (1500 mL in 70 kg adult) → hemodynamic instability

Step 4: Compensatory Mechanisms

• Sympathetic activation: Tachycardia, peripheral vasoconstriction → maintain cerebral/cardiac perfusion
• Fluid shifts: Interstitial fluid moves to intravascular compartment over 12-24 hours → dilutional anemia (initial Hb may be normal)
• Result: Temporary maintenance of BP (compensated shock), but decompensation rapid if bleeding continues

Step 5: Spontaneous Hemostasis vs. Decompensation

• If bleeding stops (70-80%): Local tamponade, platelet plug, coagulation cascade → spontaneous hemostasis
• If bleeding continues (20-30%): Hypovolemia → hypotension → reduced coronary/cerebral perfusion → shock → end-organ damage

Classification by Site

Anatomical Considerations

Why Some Sites Bleed More:

• Right colon angiodysplasia: Thin cecal wall, high intraluminal pressure during cecal contractions, degenerative vascular changes (age, chronic kidney disease, aortic stenosis via acquired von Willebrand syndrome)
• Diverticular bleeding: Vasa recta courses over diverticular dome → exposed to luminal contents → asymmetric dome formation → arterial vessel at apex erodes → massive arterial hemorrhage [5]
• Watershed areas (ischemic colitis): Splenic flexure and rectosigmoid junction have poorest collateral blood supply → vulnerable to hypoperfusion → ischemia, mucosal sloughing, bleeding

Vascular Anatomy:

• Superior mesenteric artery (SMA): Supplies jejunum, ileum, right colon to mid-transverse colon
• Inferior mesenteric artery (IMA): Supplies left colon from splenic flexure to upper rectum
• Internal iliac arteries: Supply rectum via superior, middle, inferior rectal arteries
• Marginal artery of Drummond: Collateral network connecting SMA and IMA territories
• Arc of Riolan: Meandering mesenteric artery connecting SMA and IMA (critical in ischemic colitis)

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4. Clinical Presentation

Symptoms: The Patient's Story

Typical Presentation:

• Hematochezia: Bright red or maroon blood per rectum (hallmark feature)
  • "Bright red: Usually left colon, rectum, or anus"
  • "Maroon: Usually right colon, small intestine, or rapid upper GI bleed"
  • "Blood clots: Suggests large volume bleeding"
• Blood volume: Variable (streaks on toilet paper to toilets full of blood)
• Associated symptoms:
  • "Abdominal pain: May be present (colitis, ischemia, tumor) or absent (diverticula, angiodysplasia)"
  • "Change in bowel habit: May indicate tumor or IBD"
  • "Diarrhea: Suggests colitis (infectious, ischemic, IBD)"
  • "Weakness/dizziness: Indicates significant blood loss"
  • "Syncope: Severe hypovolemia (> 30% blood volume loss)"

Presentation by Cause:

Diverticular Bleeding:

• History: Usually no prodrome; sudden onset; painless in 90%
• Bleeding: Often large volume; bright red or maroon
• Pattern: Single episode that stops spontaneously (70-80%); if continues, requires intervention [5]
• Risk factors: Age, constipation, NSAIDs, anticoagulation

Angiodysplasia:

• History: Elderly, often recurrent small bleeds over months-years
• Bleeding: Usually right colon; maroon stools; may be chronic low-grade (presenting as anemia)
• Pattern: Intermittent; may stop and recur [11]
• Associated conditions: Aortic stenosis (Heyde syndrome), chronic kidney disease, von Willebrand disease

Ischemic Colitis:

• History: Sudden onset abdominal pain (cramping, left-sided), then bloody diarrhea
• Bleeding: Maroon or bright red mixed with stool
• Risk factors: Age > 60, cardiovascular disease, hypotension, vasculopressors, cocaine use
• Pattern: Usually self-limited; severe cases → gangrene, perforation

Inflammatory Bowel Disease (UC, Crohn's):

• History: Gradual onset or acute flare; bloody diarrhea, abdominal pain, urgency, tenesmus
• Bleeding: Mixed with stool, mucus present
• Systemic symptoms: Fever, weight loss, fatigue, extraintestinal manifestations (arthritis, uveitis, skin lesions)
• Pattern: Relapsing-remitting

Colon Polyps/Tumors:

• History: Chronic occult bleeding (presenting as iron deficiency anemia) OR acute bleed from large polyp/tumor
• Bleeding: Usually small volume; may be bright red or dark
• Alarm symptoms: Weight loss, change in bowel habit, rectal mass
• Pattern: Often chronic; acute bleeding less common

Anorectal (Hemorrhoids, Fissures):

• History: Bright red blood on toilet paper, after defecation; blood on surface of stool
• Bleeding: Small volume; streaks
• Pain: Present with fissures (severe), usually absent with internal hemorrhoids
• Pattern: Intermittent; associated with straining, constipation

Signs: What You See

Vital Signs (Critical for Risk Stratification):

General Appearance:

• Pale/clammy: Significant blood loss
• Sweaty: Compensatory sympathetic response
• Distressed/confused: Severe hypovolemia affecting cerebral perfusion
• Cachexia: Suggests malignancy

Abdominal Examination:

• Tenderness: Diffuse (colitis, ischemia), localized left lower quadrant (diverticulitis, ischemic colitis), peritonitic (perforation—rare)
• Masses: Right iliac fossa (cecal tumor), left lower quadrant (sigmoid tumor)
• Bowel sounds: Normal (most cases), hyperactive (colitis), absent (ileus, severe ischemia)
• Peritonism: Rebound tenderness, guarding → suggests perforation (urgent surgical consultation)

Rectal Examination (Essential—Never Omit):

• Blood: Bright red, maroon, or mixed with stool
• Masses: Low rectal tumor, prolapsing hemorrhoids
• Tenderness: Proctitis, fissure, perianal abscess
• Empty rectum with blood on glove: Suggests proximal source (not anorectal)

Red Flags

[!CAUTION] Red Flags — Immediate Escalation Required:

• Hemodynamic instability (SBP less than 90 mmHg, HR > 100 bpm) — Indicates significant blood loss; requires aggressive resuscitation
• Ongoing active bleeding — Multiple bloody stools in short time; needs urgent investigation
• Large volume blood loss — Passing clots, toilets full of blood; may need surgery
• Altered mental status — Severe hypovolemia affecting cerebral perfusion
• Syncope or near-syncope — Indicates > 30% blood volume loss
• Postural hypotension — > 20 mmHg drop in SBP or > 30 bpm increase in HR
• Shock index > 1.0 — HR/SBP > 1.0 predicts higher mortality [16]
• Oakland score ≥9 — High risk; requires urgent intervention (colonoscopy less than 24h or CT angiography) [3,8]
• Age > 60 with hemoglobin less than 100 g/L on presentation — High-risk group
• Anticoagulation + ongoing bleeding — Consider reversal if life-threatening

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5. Clinical Examination

Structured Approach: ABCDE

A - Airway

• Assessment: Usually patent unless severely obtunded
• Action: Secure airway if GCS less than 8 or massive hematemesis (rarely occurs with LGIB alone)

B - Breathing

• Look: Respiratory rate (compensatory tachypnea if anemic/shocked), use of accessory muscles
• Listen: Chest auscultation (usually normal; bibasal crackles if fluid overload)
• Measure: SpO2 (usually normal unless severe anemia or cardiorespiratory disease)
• Action: Oxygen if SpO2 less than 94% or severe anemia (target SpO2 94-98%)

C - Circulation

• Look: Skin color (pallor), capillary refill (> 2 seconds suggests poor perfusion), jugular venous pressure (low in hypovolemia, raised if fluid overload)
• Feel: Pulse (rate, rhythm, volume), peripheral perfusion
• Listen: Heart sounds (flow murmur if severely anemic; existing murmur if aortic stenosis/Heyde syndrome)
• Measure: BP (both arms if suspecting aortic pathology), HR, postural BP (critical for volume assessment)
• Action:
  • IV access x2 (large bore 16-18G) — Essential for resuscitation
  • Fluid resuscitation — Crystalloid (balanced salt solution preferred)
  • Blood transfusion — If Hb less than 70 g/L (or less than 80 if cardiac disease) or active bleeding
  • ECG — Rule out myocardial ischemia (may be precipitated by anemia)

D - Disability

• Assessment: Glasgow Coma Scale, AVPU, pupil response
• Finding: Confusion/agitation if hypovolemic; normal if stable
• Action: Check capillary glucose; consider hypovolemia as cause of altered consciousness

E - Exposure

• Look: Full examination; stigmata of liver disease (spider nevi, palmar erythema, caput medusae—rare rectal varices if portal hypertension); signs of inflammatory bowel disease (erythema nodosum, pyoderma gangrenosum); telangiectasia (hereditary hemorrhagic telangiectasia/Osler-Weber-Rendu syndrome)
• Feel: Abdominal examination (see above)
• Action: Digital rectal examination (mandatory) — Assess for blood, masses, tenderness, stool color

Specific Examination Findings

Cardiovascular Assessment:

Postural Blood Pressure (Critical Test):

• Technique:
  1. Measure BP and HR after patient supine for 5 minutes
  2. Stand patient up and measure immediately and at 2 minutes
• Positive findings:
  • SBP drop > 20 mmHg OR HR increase > 30 bpm = significant volume loss (> 15%, approximately 750-1000 mL)
• Significance: Indicates need for fluid resuscitation; predicts worse outcomes
• Caution: May not be accurate if on beta-blockers (blunted HR response) or autonomic dysfunction (elderly, diabetes)

Shock Index:

• Calculation: HR ÷ SBP
• Interpretation:
  • "Normal: 0.5-0.7"
  • "Abnormal (shock): > 1.0 (e.g., HR 110, BP 100 → index 1.1)"
• Significance: Shock index > 1.0 predicts higher mortality and need for intervention [16]

Abdominal Examination:

• Inspection: Distension (ileus, obstruction), scars (previous surgery), visible masses, hernias
• Palpation:
  • "Tenderness: Left lower quadrant (diverticulitis, ischemic colitis), diffuse (colitis, ischemia)"
  • "Masses: Right iliac fossa (cecal tumor, Crohn's), left lower quadrant (sigmoid tumor), epigastric (gastric/pancreatic pathology if considering upper GI source)"
  • "Liver edge: Hepatomegaly (metastatic disease), cirrhosis (nodular, firm)"
• Percussion: Shifting dullness (ascites—cirrhosis, malignancy), tympanic (gaseous distension)
• Auscultation: Bowel sounds (normal, hyperactive in colitis, absent in ileus/perforation)

Rectal Examination (Essential—Never Skip):

• Purpose: Confirm bleeding, assess color, check for masses/tenderness
• Findings:
  • "Fresh bright red blood: Suggests left colon/rectal source"
  • "Maroon blood: Suggests right colon or brisk upper GI source"
  • "Melena (black tarry stool): Suggests upper GI source"
  • "Empty rectum with blood on glove: Proximal source (not anorectal)"
  • "Masses: Rectal tumor (hard, irregular, fixed), polyp (smooth)"
  • "Hemorrhoids: May palpate external hemorrhoids; internal hemorrhoids usually not palpable unless prolapsed"
  • "Tenderness: Proctitis, fissure (visible on inspection), perianal abscess"

Special Tests

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6. Investigations

Risk Stratification (CRITICAL FIRST STEP)

Risk stratification using validated scoring systems guides investigation timing, disposition, and predicts outcomes. [3,8]

Oakland Score (Validated, Recommended) [3,8]

The Oakland score predicts safe discharge and need for intervention in acute lower GI bleeding. Validated in multiple international cohorts with high sensitivity (95%) for identifying patients safe for outpatient management.

Interpretation:

• Oakland score less than 8: LOW RISK — 95% safe for outpatient management; routine colonoscopy (24-48h)
• Oakland score ≥9: HIGH RISK — Requires admission; urgent colonoscopy (less than 24h) or CT angiography if too unstable

Performance: Sensitivity 95%, specificity 30% for predicting need for intervention (transfusion, endoscopy, radiology, surgery). [8]

Clinical Application:

• Score ≥9 → Admit → Urgent colonoscopy less than 24h
• Score less than 8 + stable vitals + reliable patient → Consider discharge with urgent outpatient colonoscopy
• Score less than 8 but ongoing bleeding or unreliable patient → Admit for observation

Alternative Risk Scores

ABC Score (Alternative):

• Uses Age, Blood pressure, Comorbidities
• Predicts mortality in acute upper AND lower GI bleeding
• Less validated specifically for LGIB compared to Oakland [17]

BLEED Score:

• Uses Bleeding, Low BP, Elevated prothrombin time, Erratic mental status, Unstable comorbidities
• Less commonly used; not externally validated

First-Line (Bedside) Investigations — Do Immediately

1. Full Blood Count (FBC)

• Purpose: Assess degree of blood loss
• Findings:
  • "Hemoglobin: "
    • May be NORMAL initially (hemoconcentration; takes 12-24 hours for equilibration)
    • Serial Hb measurements critical (repeat at 4-6 hours)
    • Acute drop > 20 g/L suggests significant bleeding
  • "MCV: Normal in acute blood loss; low if chronic iron deficiency anemia (suggesting chronic occult bleeding from tumor/angiodysplasia)"
  • "Platelets: Usually normal; low if cirrhosis, bone marrow suppression, or consumption (massive transfusion)"
• Action: Repeat every 4-6 hours until stable; daily thereafter

2. Coagulation Studies

• Purpose: Assess bleeding risk and guide reversal
• Findings:
  • "INR: Elevated if on warfarin, liver disease, vitamin K deficiency"
  • "PT/aPTT: Prolonged if on anticoagulants, liver disease, factor deficiencies"
• Action: If major bleeding and INR > 1.5, consider reversal (see anticoagulation management)
• Note: Normal coagulation in most patients; abnormal suggests higher risk

3. Urea & Electrolytes, Liver Function Tests

• Purpose: Assess renal function, guide fluid management, detect liver disease
• Findings:
  • "Urea:Creatinine ratio: "
    • Usually NORMAL in lower GI bleeding (unlike upper GI bleeding where ratio > 100 suggests upper GI source from blood digestion)
    • Elevated ratio with hematochezia → consider massive upper GI bleed
  • "Creatinine: Baseline renal function; may be elevated if CKD or prerenal AKI from hypovolemia"
  • "Liver enzymes/bilirubin: Assess for cirrhosis, liver disease"
• Action: Correct electrolytes; caution with contrast if AKI

4. Group & Save / Crossmatch

• Purpose: Prepare for transfusion
• Action:
  • "Group & save: All patients (low-risk, stable)"
  • "Crossmatch 4-6 units: High-risk (Oakland ≥9, hemodynamically unstable, active bleeding)"
  • "Massive transfusion protocol: If massive bleeding (> 4 units in less than 1 hour or anticipated)"

5. Lactate

• Purpose: Marker of tissue hypoperfusion
• Findings: Lactate > 2 mmol/L suggests shock; > 4 mmol/L suggests severe shock
• Action: Aggressive resuscitation if elevated; repeat to assess response

6. ECG

• Purpose: Rule out myocardial ischemia (can be precipitated by anemia/hypotension)
• Findings: ST depression/T wave inversion (demand ischemia); arrhythmia
• Action: Troponin if ischemic changes; cardiology input if acute coronary syndrome

Imaging Investigations

Colonoscopy (First-Line Investigation) [4,12]

Colonoscopy is the first-line investigation for acute lower GI bleeding, offering both diagnostic and therapeutic capabilities.

Timing:

• Urgent (less than 24 hours): High-risk patients (Oakland ≥9, hemodynamically unstable, ongoing bleeding) [3,4]
  • Improved diagnostic yield (89-97% vs. 50-70% if delayed)
  • Reduces length of stay
  • Allows therapeutic intervention
  • "Evidence: Controversial whether urgent colonoscopy reduces mortality or rebleeding; 2023 ACG guidelines recommend less than 24h for high-risk [3,12]"
• Routine (24-48 hours): Low-risk patients (Oakland less than 8, stable, bleeding stopped)
• NOT indicated if: Ongoing massive bleeding (consider CT angiography first), hemodynamically unstable despite resuscitation (stabilize first)

Preparation:

• Rapid bowel prep: Polyethylene glycol (PEG) solution 4-6 liters over 3-4 hours
• Adequate prep improves diagnostic yield: 90% vs. 60% with poor prep
• Caution: Aspiration risk if vomiting; consider nasogastric tube

Diagnostic Findings:

Endoscopic Therapy (If Active Bleeding or Visible Vessel):

Contraindications/Cautions:

• Absolute contraindications: Perforation, peritonitis (surgery indicated)
• Relative contraindications: Severe coagulopathy (INR > 3), massive ongoing bleeding (consider CT angiography first), hemodynamic instability (resuscitate first)

CT Angiography (If Active Bleeding or Colonoscopy Negative) [6,10]

CT angiography (CTA) is highly sensitive for detecting active bleeding and guides subsequent intervention.

Indications:

• Active ongoing bleeding too brisk for safe colonoscopy
• Hemodynamically unstable despite resuscitation (perform CTA → guide angioembolization or surgery)
• Negative colonoscopy with ongoing bleeding
• Planning for angioembolization (CTA localizes bleeding site)

Technique:

• Arterial phase imaging (25-30 seconds post-contrast)
• Venous phase imaging (60-70 seconds post-contrast)
• Delayed imaging (if extravasation seen, to track extent)

Diagnostic Findings:

Advantages:

• Non-invasive
• Rapid (5-10 minutes)
• High sensitivity for active bleeding (85-90%) [6]
• Guides intervention (angiography, surgery)

Limitations:

• Requires active bleeding (> 0.3 mL/min)
• Contrast nephropathy risk (caution in CKD)
• Radiation exposure
• False negatives if bleeding intermittent

If CTA Positive (Extravasation Seen):

• Proceed to angiography with embolization (if patient stable)
• Consider surgery if unstable or embolization fails

Angiography with Embolization (If Ongoing Bleeding) [10,13]

Selective mesenteric angiography with embolization is an effective intervention for active bleeding, avoiding surgery in 60-80% of cases.

Indications:

• CTA-confirmed active bleeding (extravasation seen)
• Failed endoscopic therapy
• Contraindication to surgery (high-risk patient)

Technique:

• Selective catheterization of SMA or IMA
• Angiography to identify bleeding vessel
• Superselective embolization using coils, gelfoam, or particles
• Post-embolization angiography to confirm hemostasis

Success Rate:

• Immediate hemostasis: 70-90% [10]
• Rebleeding rate: 10-20%
• Avoidance of surgery: 60-80%

Complications:

• Colonic ischemia: 3-10% (lower if superselective embolization) [13]
  • Risk higher with IMA embolization (poor collaterals)
  • Risk lower with SMA embolization (better collaterals)
• Contrast nephropathy: 5-10% (especially if CKD)
• Access site complications: Hematoma, pseudoaneurysm (less than 2%)

Predictors of Success:

• CTA localization before angiography: Reduces procedure time, improves success
• Superselective embolization: Reduces ischemia risk vs. proximal embolization
• Experienced interventional radiologist

Nuclear Medicine Scan (Tagged Red Cell Scan) — If Intermittent Bleeding

Indications:

• Intermittent bleeding (negative colonoscopy and CTA)
• Recurrent bleeding with negative investigations
• Unable to undergo colonoscopy (e.g., severe comorbidities)

Technique:

• Technetium-99m labeled red blood cells injected IV
• Serial imaging over 24 hours
• Bleeding detected if extravasation of labeled RBCs into bowel lumen

Diagnostic Yield:

• Sensitivity: 40-60% (lower than CTA)
• Specificity: 50-70% (false positives from peristalsis moving labeled blood)
• Detects bleeding rate > 0.1 mL/min (more sensitive than CTA)

Limitations:

• Cannot localize precisely (peristalsis moves blood)
• Cannot treat (diagnostic only)
• Time-consuming (up to 24 hours)
• Low specificity (many false positives)

Modern Practice:

• Largely replaced by CTA (faster, more specific)
• Reserved for intermittent bleeding when CTA and colonoscopy negative

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7. Management

Management Algorithm

        ACUTE LOWER GI BLEEDING
    (Hematochezia - bright red/maroon blood)
                    ↓
┌─────────────────────────────────────────┐
│   IMMEDIATE ASSESSMENT (less than 5 min)       │
│  • ABCDE, IV access x2 (16-18G)         │
│  • Bloods: FBC, coag, G\u0026S, lactate       │
│  • Oakland/Birmingham score              │
│  • Digital rectal exam (MANDATORY)       │
└─────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────┐
│   RESUSCITATION                          │
│  • Crystalloid if hypotensive            │
│  • Transfuse: Hb less than 70 (less than 80 cardiac) │
│  • Reverse anticoagulation if severe     │
└─────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────┐
│   RISK STRATIFICATION                    │
├─────────────────────────────────────────┤
│  LOW RISK (Oakland less than 8)                 │
│  → Discharge if reliable                 │
│  → Routine colonoscopy 24-48h            │
│                                          │
│  HIGH RISK (Oakland ≥9 / Birmingham ≥7) │
│  → Admit, urgent colonoscopy less than 24h      │
│  → CT angiography if unstable            │
└─────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────┐
│   INVESTIGATION                          │
│  STABLE: Colonoscopy less than 24h              │
│  UNSTABLE: CT angiography                │
│  → Angioembolization or Surgery          │
└─────────────────────────────────────────┘

        ACUTE LOWER GI BLEEDING PRESENTATION
    (Hematochezia - bright red/maroon blood per rectum)
                    ↓
┌─────────────────────────────────────────────────┐
│         IMMEDIATE ASSESSMENT (less than 5 mins)          │
│  • ABCDE approach                                │
│  • IV access (large bore x2: 16-18G)            │
│  • Bloods: FBC, U&E, LFT, coag, G&S/crossmatch │
│  • Vital signs: BP, HR, postural BP             │
│  • Calculate Oakland score                       │
│  • Digital rectal examination (MANDATORY)        │
│  • Consider upper GI source if massive bleed    │
└─────────────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────────────┐
│         RESUSCITATION (Simultaneous)             │
│  • IV crystalloid (balanced salt solution)       │
│  • Transfuse if:                                │
│     - Hb less than 70 g/L (or less than 80 if cardiac disease)    │
│     - Active ongoing bleeding                    │
│     - Hemodynamic instability                    │
│  • Anticoagulation management:                  │
│     - Consider reversal if life-threatening     │
│     - Vitamin K + PCC (warfarin)                │
│     - Specific reversal agents (DOACs if avail) │
│  • Nil by mouth (prepare for endoscopy)         │
└─────────────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────────────┐
│         RISK STRATIFICATION (Oakland Score)      │
├─────────────────────────────────────────────────┤
│  LOW RISK (Oakland less than 8, stable vitals)          │
│  → Consider outpatient management if reliable   │
│  → Routine colonoscopy (24-48h)                 │
│  → Clear written instructions for return        │
│  → Follow-up arranged                            │
│                                                  │
│  HIGH RISK (Oakland ≥9, unstable, ongoing)      │
│  → Admit to medical/surgical ward or HDU/ICU    │
│  → Urgent colonoscopy (less than 24h, ideally less than 12h)      │
│  → If too unstable: CT angiography              │
│  → Monitor closely: vitals q1h, daily Hb        │
└─────────────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────────────┐
│         INVESTIGATION PATHWAY                    │
├─────────────────────────────────────────────────┤
│  STABLE / BLEEDING SLOWED:                      │
│  → Urgent colonoscopy (less than 24h) [Gold standard]    │
│     • Bowel prep: PEG 4-6L over 3-4h            │
│     • Diagnostic + therapeutic                  │
│     • Endoscopic therapy if active bleeding     │
│                                                  │
│  ONGOING MASSIVE BLEEDING / UNSTABLE:           │
│  → CT angiography (if bleeding > 0.3 mL/min)     │
│     • Identifies bleeding site                  │
│     • Guides angioembolization or surgery       │
│  → Angiography + embolization                   │
│     • If CTA shows extravasation                │
│     • 70-90% success rate                       │
│  → SURGERY (if embolization fails/unsuitable)   │
│                                                  │
│  INTERMITTENT / RECURRENT (negative studies):   │
│  → Consider small bowel source                  │
│  → Capsule endoscopy or CT enterography         │
│  → Tagged RBC scan (now rarely used)            │
└─────────────────────────────────────────────────┘
                    ↓
┌─────────────────────────────────────────────────┐
│         DEFINITIVE TREATMENT                     │
├─────────────────────────────────────────────────┤
│  ENDOSCOPIC THERAPY (if active bleeding):       │
│  → Combination therapy (clips + epinephrine)    │
│  → APC for angiodysplasia                       │
│  → Thermal coagulation (bipolar/heater probe)   │
│                                                  │
│  ANGIOGRAPHIC EMBOLIZATION:                     │
│  → If failed endoscopy or CTA-positive          │
│  → Superselective to reduce ischemia risk       │
│  → 70-90% success; 3-10% ischemia risk          │
│                                                  │
│  SURGERY (last resort):                         │
│  → Segmental resection if source localized      │
│  → Subtotal colectomy if source unknown         │
│  → Mortality 10-20% (emergency surgery)         │
└─────────────────────────────────────────────────┘

Acute/Emergency Management - The First Hour

Immediate Actions (First 15 Minutes):

1. ABCDE Assessment

   • IV access x2 (16-18G large bore) — CRITICAL for resuscitation
   • Oxygen if SpO2 less than 94%

2. Resuscitation

   • Fluids: Balanced crystalloid 500 mL bolus if hypotensive (target SBP > 90 mmHg)
   • Transfusion: Hb less than 70 g/L (less than 80 if cardiac disease); crossmatch 4-6 units if high-risk
   • Restrictive strategy: Target permissive hypotension (SBP 90-100) until bleeding controlled [18,19]

3. Investigations

   • Bloods: FBC, U\u0026E, coag, G\u0026S, lactate
   • ECG, vital signs including postural BP
   • Digital rectal examination — MANDATORY

4. Risk Stratification

   • Calculate Oakland score or Birmingham score [3,23]
   • Identify high-risk features

5. Nil by Mouth — Prepare for colonoscopy

Disposition:

Medical Management

Blood Transfusion Strategy [18,19]

Restrictive vs. Liberal Transfusion:

• Restrictive strategy (Hb less than 70 g/L): Recommended for most patients; reduces mortality and rebleeding vs. liberal strategy (Hb less than 90 g/L) [18,19]
• Exception (Hb less than 80 g/L): Cardiovascular disease (acute coronary syndrome, heart failure), severe symptoms

Massive Transfusion Protocol:

• Indication: Loss of > 50% blood volume (less than 1 hour) or > 4 units transfused with ongoing bleeding
• Components:
  • "Red cells : FFP : Platelets = 1:1:1 (balanced resuscitation)"
  • Avoid crystalloid overload (dilutional coagulopathy)
  • Monitor calcium (citrate toxicity from transfusion)
  • Monitor temperature (hypothermia)

Anticoagulation Management [3,14,20,28]

Critical Decision: Stop, Continue, or Reverse?

Anticoagulation management balances bleeding versus thromboembolic risk. Recent systematic reviews show restarting anticoagulation within 7-14 days reduces stroke/PE (NNT=30) without significantly increasing rebleeding. [20,28]

Step 1: Assess Thromboembolic Risk

Step 2: Reversal (If Life-Threatening)

Step 3: Restart Timing

• Most indications: 7-14 days when bleeding controlled and hemodynamically stable
• Very high risk (mechanical valve, recent VTE): less than 7 days
• Low risk: 14 days if recurrent bleeding concern

Antiplatelet Management

Endoscopic Management [4,12]

Indications for Therapeutic Endoscopy

High-Risk Stigmata (Forrest Classification Adapted for Colon):

• Active spurting bleeding (arterial)
• Active oozing bleeding (venous)
• Non-bleeding visible vessel (50% rebleed risk if untreated)
• Adherent clot overlying vessel (remove clot → treat if vessel underneath)

Endoscopic Techniques

Recommended Approach (Evidence-Based):

1. Active bleeding: Epinephrine injection (to slow bleeding) → Hemoclips OR thermal coagulation
2. Visible vessel: Hemoclips (first-line) OR thermal coagulation
3. Angiodysplasia: Argon plasma coagulation (APC) — 70-85% long-term success [11]
4. Post-polypectomy bleeding: Hemoclips (first-line)

Management of Specific Causes

Diverticular Bleeding: [5,9,25,29]

• 70-80% stop spontaneously — observation if stable
• Endoscopic therapy reduces rebleeding: 50% to 10% with clips + epinephrine
• Recurrence: 20-30% over 4 years; Japanese guidelines recommend considering elective resection after ≥2 transfusion-requiring episodes [25,29]
• High-dose barium therapy: RCT showed reduced recurrence and rehospitalization (investigational) [29]

Angiodysplasia: [11,26,27]

• Argon plasma coagulation: 70-85% long-term hemostasis
• Medical therapy for recurrent bleeding:
  • Octreotide (77% response rate) [26]
  • Somatostatin analogues reduce transfusion requirements (meta-analysis IRR 0.45) [27]
  • "Heyde syndrome: Consider TAVI for aortic stenosis (resolves angiodysplasia in subset)"
• Treat all visible lesions to prevent recurrence

Interventional Radiology: Angiography + Embolization [10,13]

Indications

• Failed endoscopic therapy
• CTA-confirmed active bleeding (extravasation seen)
• Ongoing bleeding too brisk for safe colonoscopy
• Patient unsuitable for surgery (high operative risk)

Technique

1. Access: Femoral artery (common femoral artery puncture)
2. Selective catheterization: SMA (for right colon, small bowel) or IMA (for left colon)
3. Angiography: Identify bleeding vessel (contrast extravasation)
4. Superselective catheterization: Advance microcatheter to bleeding vessel
5. Embolization: Coils, gelfoam, or particles
6. Post-procedure angiography: Confirm hemostasis

Outcomes

• Immediate hemostasis: 70-90% [10]
• Clinical success (avoidance of surgery): 60-80%
• Rebleeding: 10-20% (may require repeat embolization or surgery)
• 30-day mortality: 10-15% (reflects high-risk patient population)

Complications

• Colonic ischemia: 3-10% [13]
  • "Risk factors: IMA embolization (worse collaterals than SMA), proximal embolization, diabetes, cardiovascular disease"
  • "Presentation: Abdominal pain, fever, peritonitis (if transmural infarction)"
  • "Management: Conservative (if non-transmural); surgery if perforation/transmural infarction"
• Contrast-induced nephropathy: 5-10% (especially if CKD, diabetes)
• Access site complications: Hematoma, pseudoaneurysm (less than 2%)

Key to Success:

• CT angiography localization BEFORE angiography: Reduces procedure time, improves success, reduces radiation/contrast dose
• Superselective embolization: Reduces ischemia risk (3% vs. 15% with proximal embolization)

Surgical Management [13,21]

Surgery is reserved for patients who fail endoscopic and radiological therapy or have specific indications.

Indications

• Failed endoscopic therapy (persistent bleeding despite optimal endoscopy)
• Failed angiographic embolization (continued bleeding after embolization)
• Massive bleeding requiring > 6 units transfusion with hemodynamic instability
• Colonic ischemia/infarction (from embolization or ischemic colitis)
• Perforation (rare with LGIB; may occur with ischemia)
• Definitive treatment of identified lesion (e.g., tumor, large polyp unsuitable for endoscopic resection)

Procedures

Outcomes:

• Mortality: 5-10% (elective/semi-elective segmental resection) vs. 15-20% (emergency subtotal colectomy) [21]
• Morbidity: Anastomotic leak (3-5%), wound infection (5-10%), ileus (10-15%)
• Rebleeding: 3-5% (if source identified and resected) vs. 10-15% (if blind segmental resection)

Surgical Decision-Making:

• Source localized: Segmental resection (better outcomes)
• Source NOT localized:
  • If stable → continue investigation (repeat colonoscopy, capsule endoscopy for small bowel)
  • If unstable → subtotal colectomy (last resort)

Disposition & Follow-Up

Discharge Criteria:

• No active bleeding ≥24h, stable Hb, normal vitals, colonoscopy completed (or arranged if Oakland less than 8), clear anticoagulation plan, patient education, follow-up arranged

Follow-Up:

• 1-2 weeks: Review Hb, histology, anticoagulation plan, avoid NSAIDs
• 1-2 years: Surveillance colonoscopy for angiodysplasia, IBD, polyps, unclear source

Patient Education:

• Warning signs: Recurrent hematochezia, dizziness, syncope, black stools, severe pain
• Avoid NSAIDs; restart anticoagulation as planned
• High-fiber diet, hydration, smoking cessation

---

8. Complications

Immediate (Hours)

Rebleeding Risk: Active spurting at colonoscopy, age > 60, anticoagulation, diverticular (20-30%), angiodysplasia (15-30%) [9,11]

Early (Days to Weeks)

Recurrent Bleeding (10-20% within 30 days) [9,25]

• Risk factors: Diverticular, angiodysplasia, inadequate therapy
• Management: Repeat colonoscopy, CTA, angioembolization/surgery
• Prevention: Adequate endoscopic therapy, discontinue NSAIDs, consider elective resection after ≥2 transfusion episodes (diverticular) [25,29]

Colonic Ischemia (Post-Embolization) [13]

• Incidence: 3-10% (higher with IMA embolization)
• Presentation: Abdominal pain, fever, bloody diarrhea, peritonitis
• Management: Conservative (non-transmural) vs. surgery (transmural/perforation)

Hospital-Acquired: VTE (2-5%), delirium (elderly), pressure ulcers

Late (Weeks to Months)

Recurrent Bleeding (10-20% over 1-4 years) [9,25,29]

• Diverticular: 20-30% over 4 years (elective colectomy if ≥2 episodes) [25,29]
• Angiodysplasia: 15-30% over 2-5 years (repeat APC or medical therapy with octreotide/somatostatin analogues) [26,27]

Chronic Anemia (20-30%): Oral/IV iron; investigate if persistent

Post-surgical: Anastomotic leak (3-5%), obstruction (5-10%), incisional hernia (5-10%)

---

9. Prognosis & Outcomes

Natural History (Without Treatment)

Untreated Acute Lower GI Bleeding:

• Spontaneous cessation: 70-80% stop without intervention [5]
• Mortality if massive untreated bleeding: 10-20% (from hypovolemic shock, end-organ damage)
• Time course: Death within hours if massive bleeding untreated; most deaths occur in first 48 hours

Outcomes with Treatment

Prognostic Factors

Good Prognosis (Low Mortality/Rebleeding):

• Low Oakland score (less than 8) [3,8]
• Hemodynamically stable (normal BP, HR less than 100)
• Bleeding stopped at presentation
• Younger age (less than 60 years)
• No comorbidities
• Anorectal cause (hemorrhoids, fissures)—usually benign
• Successful endoscopic therapy (if active bleeding)

Poor Prognosis (High Mortality/Rebleeding):

• High Oakland score (≥9) [3,8]
• Hemodynamic instability (SBP less than 90, HR > 120, shock index > 1.0) [16]
• Age > 75 years (2-3x mortality vs. younger) [14]
• Significant comorbidities (cardiac disease, CKD, cirrhosis)
• Tumor as bleeding source (2x mortality vs. diverticular bleeding)
• Need for surgery (15-20% mortality for emergency surgery) [21]
• Rebleeding (2x mortality if rebleeds) [9]
• Anticoagulation (higher bleeding risk, more difficult management)

Prognostic Scores:

Long-Term Outcomes

1-Year Mortality: 10-15% (often from underlying comorbidities rather than bleeding itself) Recurrent Bleeding: 15-25% at 1 year (depends on cause) Quality of Life: Usually returns to baseline if bleeding controlled and underlying cause addressed

Cause-Specific Outcomes:

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10. Evidence & Guidelines

Key Guidelines

1. American College of Gastroenterology (ACG) Guidelines (2023 Update) [3]

Key Recommendations:

• Risk stratification using Oakland score — Guides safe discharge vs. admission (Strong recommendation, moderate-quality evidence)
• Urgent colonoscopy (less than 24 hours) for high-risk patients — Improves diagnostic yield, reduces length of stay (Conditional recommendation, low-quality evidence for mortality benefit)
• CT angiography for ongoing bleeding when colonoscopy not feasible — High sensitivity for active bleeding (Strong recommendation, moderate-quality evidence)
• Restrictive transfusion strategy (Hb less than 70 g/L) — Reduces mortality and rebleeding vs. liberal (Hb less than 90 g/L) (Strong recommendation, high-quality evidence) [18,19]
• Combination endoscopic therapy for high-risk stigmata — Epinephrine + mechanical/thermal (Strong recommendation, moderate-quality evidence)
• Evidence Level: Varies (1A to 2C)

2. European Society of Gastrointestinal Endoscopy (ESGE) Guidelines (2021) [22]

Key Recommendations:

• Colonoscopy within 24 hours for patients with high-risk features
• Adequate bowel preparation essential — PEG 4-6L improves diagnostic yield
• Endoscopic therapy for active bleeding or visible vessel — Clips, thermal coagulation, or combination
• Angiography with embolization if endoscopy fails or unsuitable
• Evidence Level: Varies (High to Low)

3. British Society of Gastroenterology (BSG) / Association of Coloproctology of Great Britain and Ireland (ACPGBI) Guidelines (2019)

Key Recommendations:

• Risk assessment using clinical scoring systems
• Resuscitation before investigation
• Colonoscopy first-line investigation
• Multidisciplinary approach involving gastroenterology, radiology, surgery

Landmark Trials & Studies

1. Oakland Score Derivation & Validation (2018, 2024) [3,8]

• Study: Derivation cohort (n=430) and multiple validation cohorts (international, multi-center)
• Intervention: Risk score using age, sex, previous LGIB, DRE findings, vitals, Hb
• Key Finding: Oakland score less than 8 identifies 95% of patients safe for outpatient management; score ≥9 predicts need for intervention
• Clinical Impact: Allows safe early discharge of low-risk patients; reduces admissions by 20-30%
• PMID: 38686245, 38440205

2. Early vs. Delayed Colonoscopy (Multiple Studies) [4,12]

• Studies: Several RCTs and observational studies comparing urgent (less than 24h) vs. elective (24-48h or later) colonoscopy
• Key Findings:
  • "Diagnostic yield: Higher with urgent colonoscopy (89-97% vs. 50-70%)"
  • "Length of stay: Reduced with urgent colonoscopy (3 vs. 5 days)"
  • "Rebleeding/Mortality: NO significant difference in RCTs (controversial)"
• Clinical Impact: Most guidelines recommend urgent colonoscopy for high-risk, but evidence for mortality benefit weak
• PMID: 36735555, 28262219

3. Restrictive vs. Liberal Transfusion in GI Bleeding (2017, 2021) [18,19]

• Study: Cochrane systematic review and meta-analysis (RCTs in GI bleeding)
• Intervention: Restrictive (Hb less than 70 g/L) vs. liberal (Hb less than 90 g/L) transfusion strategy
• Key Finding: Restrictive strategy reduces:
  • "All-cause mortality: RR 0.65 (95% CI 0.44-0.97)"
  • "Rebleeding: RR 0.64 (95% CI 0.45-0.90)"
  • "Adverse events: Fewer transfusion reactions, less fluid overload"
• Clinical Impact: Changed transfusion practice worldwide; restrictive now standard
• PMID: 28397699, 34932836

4. CT Angiography Diagnostic Accuracy (Multiple Studies) [6,10]

• Studies: Systematic reviews of CTA performance in lower GI bleeding
• Key Findings:
  • "Sensitivity: 85-90% (if bleeding rate > 0.3 mL/min)"
  • "Specificity: 95%"
  • "Positive predictive value: 90-95% (extravasation seen = intervention needed)"
• Clinical Impact: CTA guides angioembolization, improves success rate, reduces ischemia risk vs. blind angiography
• PMID: 35240106, 29883267

5. Angiographic Embolization Outcomes (2019, 2022) [10,13]

• Studies: Large cohort studies and systematic reviews
• Key Findings:
  • "Immediate hemostasis: 70-90%"
  • "Avoidance of surgery: 60-80%"
  • "Ischemia risk: 3-10% (lower with superselective embolization)"
• Clinical Impact: Embolization preferred over surgery in suitable patients; requires CTA localization for best outcomes
• PMID: 31589996

6. Resumption of Anticoagulation After GI Bleeding (2023) [20]

• Studies: Observational studies and meta-analyses
• Key Finding: Restarting anticoagulation within 7-30 days reduces thromboembolic events (stroke, VTE) without significantly increasing major rebleeding
  • "Number needed to treat (NNT): 30 to prevent one stroke"
  • "Number needed to harm (NNH): Not significantly increased"
• Clinical Impact: Most patients should restart anticoagulation after bleeding controlled; timing depends on thromboembolic risk
• PMID: 36735555

Evidence Strength Summary

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11. Patient/Layperson Explanation

What is Acute Lower GI Bleeding?

Lower GI bleeding means bleeding from your small intestine, colon (large intestine), rectum, or anus. You'll see fresh blood when passing stools—bright red (bleeding lower down) or dark maroon (bleeding higher up). This differs from vomiting blood or black tarry stools (stomach bleeding).

Common causes:

• Small pouches in colon (diverticula) that rupture into blood vessels
• Abnormal blood vessels (angiodysplasia)
• Colon inflammation (colitis)
• Hemorrhoids or anal fissures
• Tumors or polyps

Why it matters

You can lose blood quickly, depriving vital organs of oxygen. Most bleeds (70-80%) stop naturally, but some need urgent treatment. With modern care—fluids, transfusions, camera tests—96-98% recover fully. Mortality is 2-4% overall, rising to 10-15% in elderly/very sick patients.

Treatment

1. Stabilization: Fluids/blood through drip; risk score calculated (Oakland score) for disposition

2. Investigation:

• Colonoscopy (camera through bottom): Finds bleeding in 90%; sedation given
• CT scan with dye: If too active for colonoscopy

3. Stopping Bleeding:

• Colonoscopy: Clips or heat treatment (85-95% success)
• Angioembolization: Block vessel via groin artery (70-90% success; 3-10% ischemia risk)
• Surgery: Rarely needed (5-10%)

Recovery

Most stay 3-5 days in hospital. After discharge: avoid NSAIDs, high-fiber diet, restart blood thinners as directed. Return if rebleeding, dizziness, or severe pain. Recurrence: 15-25% within 1 year (depends on cause).

In Hospital: First hours: fluids, tests, maybe transfusion (nothing by mouth). Day 1: Colonoscopy (sedated). Days 1-3: Monitoring vitals, repeat bloods. Days 3-5: Discharge if stable (or same/next day if low-risk).

After Discharge: Normal diet (high-fiber if diverticular disease); stop NSAIDs; restart blood thinners per doctor (1-2 weeks); iron if anemic; follow-up 1-2 weeks; lifestyle changes (stop smoking, hydration, avoid straining).

Recovery: Hospital 1-5 days; feel normal 1-2 weeks; full energy 4-8 weeks.

When to seek help

Call 999 IMMEDIATELY: Lots of blood, very weak/dizzy/faint, racing heart, confusion, syncope

See doctor URGENTLY (same day): Recurrent bleeding, on blood thinners with bleeding, ongoing pain, weight loss

See doctor SOON (few days): Small blood on paper, black stools, tired/pale

Remember: Early treatment saves lives.

---

12. Differential Diagnosis

Conditions to Consider

Acute lower GI bleeding must be distinguished from other causes of rectal bleeding and from upper GI bleeding presenting atypically.

Upper GI Bleeding Presenting as Hematochezia

Critical Point: 10-15% of patients presenting with bright red blood per rectum actually have massive upper GI bleeding (blood transits rapidly through gut without digestion). [7]

When to Suspect Upper GI Source:

• Hemodynamic instability (SBP less than 90, HR > 120)
• Very large volume bleeding (toilets full of blood, multiple episodes in short time)
• Elevated urea:creatinine ratio > 100 (blood digested in small bowel → urea absorption)
• History of peptic ulcer disease, liver disease, varices, recent NSAID use
• Nasogastric aspirate shows blood (though absence doesn't exclude upper GI source)

Management:

• Upper endoscopy (OGD) BEFORE colonoscopy if strong suspicion
• Treat as upper GI bleeding: High-dose PPI, endoscopic therapy, ICU monitoring

Differentiating Key Lower GI Causes

1. Diverticular vs. Angiodysplasia

2. Ischemic Colitis vs. Inflammatory Bowel Disease (IBD)

3. Benign vs. Malignant Bleeding

"Can't Miss" Diagnoses

1. Massive Upper GI Bleeding (Masquerading as LGIB):

• Clue: Hemodynamic instability, very rapid bleeding, elevated urea:creatinine ratio
• Key: Don't assume lower GI just because bright red blood—always consider upper GI source if massive bleeding
• Investigation: Upper endoscopy (OGD) first if suspected
• Management: High-dose PPI, endoscopic therapy (clips, cautery), ICU monitoring

2. Colorectal Cancer:

• Clue: Weight loss, change in bowel habit, chronic anemia, age > 50
• Key: Colonoscopy with biopsy mandatory in all cases to exclude malignancy
• Investigation: Colonoscopy with biopsy, CT staging (chest/abdomen/pelvis) if cancer confirmed, CEA tumor marker
• Management: Surgical resection (curative if localized), chemotherapy (if metastatic)

3. Ischemic Colitis:

• Clue: Sudden onset severe cramping left-sided pain, bloody diarrhea, cardiovascular risk factors, recent hypotension
• Key: Can progress to transmural infarction, perforation, sepsis—requires urgent recognition
• Investigation: Colonoscopy (segmental erythema, ulceration at watershed areas), CT (bowel wall thickening, pneumatosis if severe)
• Management:
  • "Non-transmural: Conservative (NBM, IV fluids, antibiotics if sepsis)"
  • "Transmural/perforation: Emergency surgery (resection)"

4. Inflammatory Bowel Disease (Severe Flare/Toxic Megacolon):

• Clue: Bloody diarrhea (> 6 stools/day), fever, tachycardia, abdominal distension, systemic toxicity
• Key: Toxic megacolon (colon diameter > 6 cm) → high risk of perforation → mortality 20-30%
• Investigation: Colonoscopy (limited exam to avoid perforation), AXR (colon diameter), CT (if perforation suspected)
• Management:
  • "Severe flare: IV steroids, NBM, IV fluids; biologics (infliximab) if no response in 3-5 days"
  • "Toxic megacolon: Surgery (subtotal colectomy) if no improvement or perforation"

5. Meckel's Diverticulum (in Younger Patients):

• Clue: Painless rectal bleeding, age less than 30, large volume
• Key: Most common congenital GI anomaly; contains ectopic gastric mucosa → ulceration → bleeding
• Investigation: Technetium-99m pertechnetate scan (Meckel's scan)—detects ectopic gastric mucosa (sensitivity 85-90% in children, lower in adults)
• Management: Surgical resection (laparoscopic or open)

---

13. Prevention & Risk Reduction

Primary Prevention

Primary prevention focuses on reducing the risk of developing lower GI bleeding in at-risk populations.

Dietary Measures:

• High-fiber diet: Fruits, vegetables, whole grains, legumes (target 25-30 g fiber/day)
  • "Evidence: Reduces diverticular complications (not diverticulosis formation itself)"
  • "Note: Once bleeding occurs, fiber doesn't prevent rebleeding; focus on avoiding NSAIDs"
• Adequate hydration: 2-3 liters/day (prevents constipation)
• Avoid alcohol excess: Heavy alcohol → portal hypertension, coagulopathy

Medication Review:

• NSAIDs: Stop if possible; if needed, use lowest dose for shortest time + PPI
• Anticoagulants: Use only if indicated; regular INR monitoring (warfarin); prefer DOACs if suitable (lower GI bleeding risk than warfarin in some studies)
• Antiplatelets: Use only if indicated (secondary prevention of cardiovascular events); avoid if primary prevention and high GI risk

Secondary Prevention (Preventing Rebleeding After First Episode)

For patients who have had one episode of lower GI bleeding, preventing recurrence is critical.

1. Treat Underlying Cause

2. Medication Optimization

Anticoagulation/Antiplatelet Review:

Key Principle: Balance bleeding risk vs. thromboembolic risk. [20]

Evidence: Resuming anticoagulation reduces thromboembolic events (stroke, VTE) by 50-70% without significantly increasing major rebleeding. NNT to prevent one stroke = 30. [20]

3. Surveillance Colonoscopy

For patients at high risk of recurrence or to ensure no missed lesions:

Tertiary Prevention (Managing Recurrent Bleeding)

For patients with recurrent bleeding despite optimal management:

1. Angiodysplasia (Recurrent Despite Endoscopic Therapy)

Medical Therapy (Limited Evidence):

• Estrogen-progesterone: May reduce bleeding frequency (mechanism: improves vascular integrity)
  • "Dose: Estrogen 0.625 mg + progesterone 2.5 mg daily"
  • "Evidence: Small studies; efficacy uncertain; side effects (thrombosis, cancer risk)"
• Octreotide: Somatostatin analogue; may reduce bleeding in selected cases
  • "Dose: 50-100 mcg SC twice daily"
  • "Evidence: Very limited; case reports/small series"
• Thalidomide: Anti-angiogenic; may reduce bleeding
  • "Evidence: Very limited; significant side effects (teratogenicity, neuropathy)"
• Tranexamic acid: Antifibrinolytic
  • "Evidence: Very limited for angiodysplasia specifically"

Surgical Therapy:

• Right hemicolectomy: If recurrent bleeding localized to right colon despite repeated APC
• Evidence: 90%+ reduction in rebleeding, but significant operative morbidity (10-20%)
• Consider if: > 3 episodes requiring transfusion, multiple APC sessions failed

2. Diverticular Bleeding (Recurrent)

Elective Colectomy:

• Indication: > 2 episodes requiring transfusion, or 1 massive episode requiring > 4 units
• Procedure: Segmental resection (if bleeding site localized) OR left hemicolectomy (if left-sided diverticulosis)
• Outcomes:
  • "Rebleeding: less than 5% (if source localized and resected)"
  • "Mortality: 1-2% (elective surgery)"
  • "Morbidity: 10-20% (anastomotic leak, infection, ileus)"
• Evidence: Moderate; based on cohort studies; no RCTs

Decision: Balance surgical risk vs. bleeding risk; individualize based on patient age, comorbidities, quality of life

3. IBD (Recurrent Flares with Bleeding)

Optimize Medical Therapy:

• Step-up approach: 5-ASA → steroids → immunosuppression (azathioprine, mercaptopurine) → biologics (anti-TNF, anti-integrin)
• Monitor closely: Colonoscopy every 1-2 years; fecal calprotectin
• Surgery if medically refractory: Subtotal colectomy (UC), segmental resection (Crohn's)

4. General Measures for Recurrent Bleeding

• Iron supplementation: Oral (ferrous sulfate 200 mg TDS) or IV (if oral not tolerated)
• Avoid triggers: NSAIDs, excessive alcohol, smoking
• Patient education: Warning signs, when to seek help, emergency plan
• Hematology input: If recurrent bleeding + anemia despite therapy (consider bleeding disorder, platelet dysfunction)

---

14. Special Populations

Elderly Patients (> 75 years)

Specific Considerations:

• Higher mortality (10-15% vs. 2-4%) [14]
• Comorbidities (CVD 50%, CKD 30%)
• Polypharmacy, anticoagulants/antiplatelets
• Frailty, reduced reserve
• Atypical presentation (may not mount tachycardia; confusion common)

Management Adjustments:

Common Causes: Angiodysplasia, diverticular, ischemic colitis, tumors

Key Challenges: Frailty assessment (CFS), goals of care, medication review, delirium prevention

Patients on Anticoagulation [14,20,28]

Prevalence: 20-30% of LGIB patients

Critical Decisions:

1. Stop/Continue? See Anticoagulation Management section—balance thrombotic vs. bleeding risk
2. Reversal: Warfarin (Vit K + PCC), Dabigatran (idarucizumab), Rivaroxaban/Apixaban (andexanet/PCC)
3. Restart: 7-30 days based on thrombotic risk; NNT=30 to prevent stroke without significant rebleeding increase [20,28]

Patients with IBD [3]

Specific Considerations: Bleeding may indicate flare; immunosuppression complicates care; cancer risk (UC > 8-10 years)

Assess Disease Activity: Truelove \u0026 Witts (UC), Harvey-Bradshaw (Crohn's)

Investigation: Colonoscopy + biopsy; exclude infection (C. diff, CMV); imaging if Crohn's

Management:

Complications: Toxic megacolon (colon 6cm, 20-30% mortality), perforation, massive bleeding (rare, less than 5%)

Patients with CKD [14]

Specific Considerations: Uremic platelet dysfunction, baseline anemia, fluid balance critical, contrast nephropathy risk

Management Adjustments:

Anemia Management: Optimize EPO, IV iron, dialysis optimization

Patients with Liver Disease/Cirrhosis

Specific Considerations: Coagulopathy (INR often elevated), thrombocytopenia, portal hypertension (rectal varices), ascites/SBP risk

Management Adjustments:

---

Endoscopy: Higher risk (sedation → encephalopathy, hypotension); ICU/HDU if Child-Pugh C; lactulose prophylaxis

Monitor Decompensation: Encephalopathy (lactulose, rifaximin), hepatorenal syndrome (terlipressin + albumin), SBP (ciprofloxacin/norfloxacin prophylaxis; diagnostic paracentesis)

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Last Reviewed: 2026-01-10 | MedVellum Editorial Team

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15. References

Primary Guidelines

1. Longstreth GF. Epidemiology and outcome of patients hospitalized with acute lower gastrointestinal hemorrhage: a population-based study. Am J Gastroenterol. 1997;92(3):419-424.

2. Strate LL, Ayanian JZ, Kotler G, Syngal S. Risk factors for mortality in lower intestinal bleeding. Clin Gastroenterol Hepatol. 2008;6(9):1004-1010.

3. Sengupta N, Feuerstein JD, Jairath V, et al. Management of Patients With Acute Lower Gastrointestinal Bleeding: An Updated ACG Guideline. Am J Gastroenterol. 2023;118(2):208-231. PMID: 36735555

4. Green BT, Rockey DC, Portwood G, et al. Urgent colonoscopy for evaluation and management of acute lower gastrointestinal hemorrhage: a randomized controlled trial. Am J Gastroenterol. 2005;100(11):2395-2402. PMID: 16279895

5. Strate LL. Lower GI bleeding: epidemiology and diagnosis. Gastroenterol Clin North Am. 2005;34(4):643-664. PMID: 16303575

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Further Resources

• American College of Gastroenterology (ACG): https://gi.org — Guidelines, clinical tools
• European Society of Gastrointestinal Endoscopy (ESGE): https://www.esge.com — Guidelines, educational resources
• British Society of Gastroenterology (BSG): https://www.bsg.org.uk — UK guidelines
• Oakland Score Calculator: Available online (validate before clinical use)

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists. This information is not a substitute for professional medical advice, diagnosis, or treatment.