What is the initial management for a patient presenting with a lower gastrointestinal (GI) bleed?

Initial Management of Lower Gastrointestinal Bleeding

For hemodynamically unstable patients (shock index >1), immediately perform CT angiography to localize bleeding, followed by catheter angiography with embolization within 60 minutes—colonoscopy should be avoided in this setting. 1, 2

Immediate Assessment and Resuscitation

Calculate shock index (heart rate ÷ systolic blood pressure) at presentation:

• Shock index >1 defines hemodynamic instability and mandates urgent intervention rather than routine colonoscopy 1, 2, 3
• Place at least two large-bore IV catheters for rapid volume expansion 3
• Initiate aggressive fluid resuscitation with crystalloids 3

Perform digital rectal examination to confirm blood in stool, exclude anorectal pathology, and assess for bright red blood that may indicate an anorectal source 1, 2

Always consider an upper GI source in patients with hemodynamic instability, as brisk rectal bleeding with shock may represent upper GI bleeding—failure to consider this leads to delayed diagnosis 1, 2, 3

Risk Stratification for Stable Patients

For hemodynamically stable patients, calculate the Oakland score (incorporating age, gender, previous LGIB admission, digital rectal exam findings, heart rate, systolic BP, and hemoglobin): 2, 4

• Oakland score ≤8 points: Safe for discharge with urgent outpatient investigation 2, 4
• Oakland score >8 points: Requires hospital admission for colonoscopy 2, 4

Transfusion Strategy

Use restrictive transfusion thresholds for most patients: 2, 3, 4

• Without cardiovascular disease: Hemoglobin trigger 70 g/L, target 70-90 g/L 2, 4
• With cardiovascular disease: Hemoglobin trigger 80 g/L, target ≥100 g/L 2, 4

Diagnostic Approach Based on Hemodynamic Status

Hemodynamically Unstable Patients (Shock Index >1)

CT angiography is the first-line investigation as it provides the fastest, least invasive means to localize bleeding and can identify upper GI, small bowel, or colonic sources without requiring bowel preparation 1, 2, 3

Following positive CTA, proceed immediately to catheter angiography with embolization within 60 minutes in centers with 24/7 interventional radiology 2, 5

Do not perform colonoscopy in unstable patients—the British Society of Gastroenterology explicitly recommends against colonoscopy when shock index >1, as it requires bowel preparation, cannot identify upper GI or small bowel sources, and delays definitive therapy 1, 2

If CTA identifies no lower GI source, perform upper endoscopy immediately as hemodynamic instability with hematochezia may indicate upper GI bleeding 1, 3

Hemodynamically Stable Patients

Colonoscopy should be performed within 24 hours after adequate bowel preparation as the initial diagnostic and therapeutic procedure 4, 6

The optimal timing remains uncertain—one RCT showed no advantage of urgent (<12 hours) versus elective (36-60 hours) colonoscopy for diagnostic yield, therapeutic yield, length of stay, or transfusion requirements 1

Anticoagulation Management

For patients on warfarin with unstable GI hemorrhage: 2, 5, 4

• Interrupt warfarin immediately at presentation 2, 5
• Reverse with prothrombin complex concentrate (PCC) and vitamin K; use fresh frozen plasma only if PCC unavailable 2, 4
• Restart warfarin 7 days after hemorrhage in patients with low thrombotic risk 2, 5

For patients on direct oral anticoagulants: Temporarily withhold at presentation 4

Antiplatelet Management

For aspirin therapy: 2, 5, 4

• Primary prophylaxis: Permanently discontinue 2, 5
• Secondary prevention: Do not routinely stop; if stopped, restart as soon as hemostasis is achieved, preferably within 5 days 2, 4, 6

For dual antiplatelet therapy: Continue aspirin; the P2Y12 receptor antagonist can be continued or temporarily interrupted based on bleeding severity and ischemic risk, but if stopped, restart within 5 days 2, 4

Critical Pitfalls to Avoid

Performing colonoscopy in unstable patients delays definitive diagnosis and treatment—CTA localizes bleeding faster and guides appropriate intervention 1, 2

Failing to exclude an upper GI source in patients with hemodynamic instability and hematochezia leads to missed diagnoses, as up to 11% of apparent lower GI bleeds originate from the upper GI tract 1, 3

Underestimating mortality risk: While overall in-hospital mortality is 3.4%, it rises to 18% for inpatient-onset LGIB and 20% for patients requiring ≥4 units of red cells—mortality relates primarily to comorbidity rather than exsanguination 2, 5