What are the etiology, clinical presentation, diagnostic workup, and management of a lower gastrointestinal bleed for a Canadian OSCE?

Lower Gastrointestinal Bleeding: OSCE Guide

ETIOLOGY

The most common causes of lower GI bleeding are diverticulosis (40% of cases), followed by hemorrhoids, angiodysplasia, ischemic colitis, post-polypectomy bleeding, and inflammatory bowel disease 1, 2, 3.

Common Causes by Frequency:

• Diverticulosis: 40% of cases, most common in Western populations
• Anorectal disorders: Hemorrhoids, anal fissures
• Angiodysplasia: Particularly in elderly patients
• Ischemic colitis: Associated with vascular disease
• Post-endoscopic complications: Following polypectomy or biopsy
• Inflammatory bowel disease: Ulcerative colitis, Crohn's disease
• Malignancy: Colorectal cancer
• Infectious colitis: Various bacterial/viral pathogens

Risk Factors:

• Age >50 years
• Prior history of LGIB
• Anticoagulation or antiplatelet therapy
• Cardiovascular disease
• Prolonged bed rest (in frail elderly)

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CLINICAL PRESENTATION

Patients typically present with hematochezia (bright red blood per rectum), though melena can occur with proximal colonic bleeding, or occult bleeding detected on laboratory testing 4.

Key Symptoms to Identify:

• Hematochezia: Bright red blood or maroon stools (most common)
• Melena: Dark, tarry stools (suggests slower bleeding or right colon source)
• Blood clots per rectum: Associated with more severe bleeding
• Abdominal pain: May suggest ischemic colitis or inflammatory causes
• Diarrhea: Suggests infectious or inflammatory etiology
• Syncope/presyncope: Indicates significant blood loss

Critical History Elements:

• Hemodynamic symptoms: Dizziness, syncope, chest pain
• Medication history: Anticoagulants, antiplatelets, NSAIDs
• Comorbidities: Cardiovascular disease, prior GI bleeding, liver disease
• Recent procedures: Colonoscopy, enemas, anorectal instrumentation (can cause catastrophic bleeding in frail patients) 5

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DIAGNOSTIC WORKUP

Immediately stratify patients as unstable (shock index >1) or stable, then categorize stable bleeds as major or minor using the Oakland score 1.

Initial Assessment:

Hemodynamic Parameters:

• Shock Index = Heart Rate ÷ Systolic BP
  • >1 = Unstable (e.g., HR 110, BP 100 = SI 1.1)
  • ≤1 = Stable
• Vital signs: BP, HR, orthostatic changes
• Physical examination including digital rectal examination (mandatory)

Laboratory Markers:

• Complete blood count (hemoglobin, hematocrit)
• Coagulation profile (INR, PTT)
• Type and crossmatch
• Lactate (if unstable)

Risk Stratification:

Oakland Score (for stable patients):

• ≤8 points: Minor self-terminating bleed → discharge for urgent outpatient investigation 1, 6
• >8 points: Major bleed → admit for inpatient colonoscopy 1

Components include: age, sex, prior LGIB, digital rectal examination findings, heart rate, systolic BP, hemoglobin

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DIAGNOSTIC ALGORITHM

For UNSTABLE Patients (Shock Index >1):

1. Immediate resuscitation with IV crystalloids

2. CT Angiography (CTA) is the first-line diagnostic test 1

• Fastest and least invasive method to localize bleeding
• Guides endoscopic or radiological therapy
• Should be performed before any intervention

3. If CTA is negative, perform upper endoscopy immediately 1

• LGIB with hemodynamic instability may indicate upper GI source
• Rule out brisk upper GI bleed presenting as hematochezia

4. If CTA is positive, proceed to catheter angiography with embolization within 60 minutes 1

For STABLE Patients:

1. Colonoscopy is the reference diagnostic and therapeutic procedure 1, 6

• Perform within 24 hours (not emergently)
• Requires adequate bowel preparation
• Both diagnostic and therapeutic capability

2. If colonoscopy fails or cannot be performed:

• Consider CTA if bleeding persists
• Repeat colonoscopy if needed
• Arterial embolization as escalation

Common Pitfall: Do NOT rush to emergency colonoscopy in stable patients—early colonoscopy has not demonstrated improved patient outcomes, and adequate bowel preparation is essential 6, 3.

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MANAGEMENT

Resuscitation:

Blood Transfusion Strategy 1, 6:

• Stable patients WITHOUT cardiovascular disease:

  • Transfuse at Hb ≤70 g/L
  • Target Hb 70-90 g/L post-transfusion

• Stable patients WITH cardiovascular disease:

  • Transfuse at Hb ≤80 g/L
  • Target Hb ≥100 g/L post-transfusion

• Unstable patients with active bleeding:

  • Emergent transfusion regardless of hemoglobin level
  • Massive transfusion protocol if needed

Fluid Resuscitation:

• Normal saline or balanced crystalloids
• Goal: normalize heart rate and blood pressure before procedures

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Anticoagulation/Antiplatelet Management:

Warfarin 1, 6:

• Interrupt immediately at presentation
• Unstable bleeding: Reverse with prothrombin complex concentrate (PCC) + IV vitamin K (not just vitamin K alone)
• Low thrombotic risk: Restart at 7 days post-hemorrhage
• High thrombotic risk (prosthetic mitral valve, recent VTE <3 months): Consider LMWH at 48 hours

Direct Oral Anticoagulants (DOACs) 6:

• Temporarily withhold at presentation
• Consider reversal agents if unstable

Aspirin 1, 6:

• Secondary prevention: DO NOT routinely stop—restart as soon as hemostasis achieved or within 5 days
• Primary prevention: Permanently discontinue

Dual Antiplatelet Therapy (DAPT) 1, 6:

• Continue aspirin
• P2Y12 inhibitor (clopidogrel, ticagrelor): Can continue or temporarily interrupt based on severity and ischemic risk
• Consult cardiology before discontinuing DAPT
• If interrupted, restart P2Y12 inhibitor within 5 days

Critical Pitfall: Never stop aspirin or DAPT without cardiology consultation in patients with recent cardiac stenting—the thrombotic risk may outweigh bleeding risk 6.

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Therapeutic Interventions:

Endoscopic Therapy (during colonoscopy):

• Epinephrine injection
• Hemoclip application
• Thermal coagulation (bipolar, heater probe)
• Band ligation (for hemorrhoids)

Radiological Therapy:

• Catheter angiography with embolization for positive CTA
• Should be available within 60 minutes for unstable patients 1

Surgical Intervention:

• LAST RESORT ONLY 1
• Never proceed to emergency laparotomy unless every effort has been made to localize bleeding by radiological and/or endoscopic modalities
• Reserved for uncontrolled severe bleeding or multiple failed interventions

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Disposition:

Discharge Criteria 1:

• Oakland score ≤8 points
• Self-terminating bleed
• Hemodynamically stable
• No other indications for admission
• Arrange urgent outpatient colonoscopy

Admission Criteria:

• Oakland score >8 points
• Major bleed
• Hemodynamic instability
• Significant comorbidities
• Need for transfusion or intervention

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KEY PITFALLS TO AVOID

1. Do not perform emergency colonoscopy in unstable patients—stabilize first and obtain CTA 1

2. Do not forget to consider upper GI source in unstable LGIB—perform upper endoscopy if CTA negative 1

3. Do not stop aspirin for secondary prevention—the cardiovascular risk outweighs bleeding risk 6

4. Do not proceed to surgery without exhausting endoscopic/radiological options 1

5. Do not use nuclear scintigraphy routinely—CTA is superior for localization 3

6. Do not over-transfuse stable patients—use restrictive thresholds (Hb 70 g/L) 1

7. Be aware that routine anorectal procedures (enemas, catheters) can cause catastrophic bleeding in frail, elderly, bedridden patients—maintain high suspicion and proceed directly to colonoscopy if massive bleeding occurs post-procedure 5