How should an adult with acute lower gastrointestinal bleeding be evaluated and treated, including resuscitation, anticoagulation reversal, imaging, colonoscopy, and endoscopic or angiographic therapy?

Management of Acute Lower Gastrointestinal Bleeding

Immediate Hemodynamic Assessment and Resuscitation

Calculate the shock index (heart rate ÷ systolic blood pressure) immediately upon presentation; a shock index >1 defines hemodynamic instability and mandates CT angiography rather than colonoscopy as the first diagnostic test. 1

Resuscitation Protocol

• Place two large-bore intravenous catheters and initiate aggressive crystalloid resuscitation (normal saline or Ringer's lactate) to restore blood pressure and heart rate before any diagnostic procedure. 1, 2

• Apply a restrictive transfusion strategy: transfuse packed red blood cells when hemoglobin falls below 70 g/L in patients without cardiovascular disease, targeting 70–90 g/L. 1, 3

• For patients with cardiovascular disease, use a higher threshold of 80 g/L and target ≥100 g/L. 1, 3

• Correct coagulopathy immediately: transfuse fresh frozen plasma when INR >1.5 and platelets when platelet count <50 × 10⁹/L. 1

Anticoagulation and Antiplatelet Management

Warfarin

• Interrupt warfarin immediately at presentation. 1, 3

• For unstable hemorrhage, reverse with 4-factor prothrombin complex concentrate (PCC) plus low-dose vitamin K (<5 mg IV). Do not use fresh frozen plasma as first-line therapy—it requires ABO matching, has slower infusion rates, and increases volume overload risk. 1, 3

• Restart warfarin at 7 days after hemorrhage for patients with low thrombotic risk, or at 3 days for high thrombotic risk (e.g., mechanical mitral valve). 1

Direct Oral Anticoagulants (DOACs)

• Interrupt DOAC therapy immediately at presentation. 1, 3

• For life-threatening hemorrhage, administer specific reversal agents: idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors. 1

• Restart DOAC at maximum 7 days after hemorrhage. 1

Antiplatelet Therapy

• Aspirin for secondary cardiovascular prevention should NOT be routinely stopped; if stopped, restart as soon as hemostasis is achieved or within 5 days. 1, 3

• Aspirin for primary prophylaxis should be permanently discontinued. 1

• For dual antiplatelet therapy, continue aspirin; the P2Y12 inhibitor may be continued or temporarily held based on bleeding severity and ischemic risk, but restart within 5 days if interrupted. 1, 3

Diagnostic Pathway for Hemodynamically Unstable Patients (Shock Index >1)

CT Angiography as First-Line

CT angiography (CTA) should be performed immediately as the first diagnostic test—NOT colonoscopy—in hemodynamically unstable patients. 1, 2

• CTA provides the fastest and least invasive means to localize bleeding, with a sensitivity of 94% and ability to detect bleeding rates as low as 0.3 mL/min. 1

• Perform arterial-phase imaging only; do not use delayed/portal-venous phases or positive oral contrast, as these mask extravasation. 2

• Colonoscopy is explicitly contraindicated when shock index >1 because it requires 4–6 L of polyethylene glycol bowel preparation over 3–4 hours, sedation that can worsen shock, and does not address massive bleeding. 1

Endovascular Intervention

• When CTA identifies a bleeding source, catheter angiography with embolization should be performed within 60 minutes in centers with 24/7 interventional radiology services. 1

• Transcatheter embolization achieves immediate hemostasis in 40–100% of cases and provides time to stabilize the patient and prepare the bowel for possible later surgery. 1

Upper GI Source Exclusion

• If CTA shows no lower GI source, perform urgent upper endoscopy because 10–15% of severe hematochezia originates from the upper gastrointestinal tract, especially in patients with hemodynamic instability, prior peptic ulcer disease, or portal hypertension. 1, 4

• Nasogastric tube placement is unnecessary when maroon-colored stool strongly suggests a lower GI source; reserve NGT only for cases where an upper GI source is strongly suspected. 1

Surgical Intervention (Last Resort Only)

• Surgery is reserved only for patients who remain unstable despite successful localization and endovascular therapy, or after failure of angiographic embolization. 1

• Blind segmental resection or emergency subtotal colectomy without prior localization carries rebleeding rates up to 33% and mortality of 33–57%, compared with ~10% when bleeding is first localized. 1

Diagnostic Pathway for Hemodynamically Stable Patients (Shock Index ≤1)

Initial Assessment

• Perform digital rectal examination to confirm blood in stool and exclude anorectal pathology, which accounts for approximately 16.7% of diagnoses. 1

• Check for orthostatic hypotension, which indicates significant blood loss requiring ICU admission. 1

Risk Stratification with Oakland Score

Calculate the Oakland score (incorporates age, gender, previous LGIB admission, digital rectal examination findings, heart rate, systolic blood pressure, and hemoglobin level): 1

• Oakland score ≤8 points: Discharge for urgent outpatient colonoscopy within 2 weeks (approximately 6% have underlying bowel cancer). 1

• Oakland score >8 points: Admit for inpatient colonoscopy on the next available list. 1

Colonoscopy Timing and Preparation

Urgent colonoscopy within 24 hours does NOT improve rebleeding, mortality, or length of stay compared with elective colonoscopy. Schedule colonoscopy on the next available inpatient list for stable patients. 1, 3, 5

• Provide adequate bowel preparation with 4–6 L of polyethylene glycol administered over 3–4 hours. 1, 5

• Inadequate preparation leads to missed lesions, repeat procedures, and diagnostic failure rates up to 70%. 1

If Colonoscopy is Negative

• When colonoscopy fails to identify a definitive bleeding source and bleeding persists, perform upper endoscopy next—especially if the patient has a history of syncope, low blood pressure, BUN/creatinine ratio ≥30, or low albumin. 4

• Capsule endoscopy may be considered for patients without severe bleeding features, particularly those without colonic diverticula. 4

ICU Admission Criteria

Admit to ICU if any of the following are present: 1

• Orthostatic hypotension
• Hematocrit decrease ≥6%
• Transfusion requirement >2 units packed red blood cells
• Continuous active bleeding
• Persistent hemodynamic instability despite aggressive resuscitation

Critical Pitfalls to Avoid

• Do not rush to colonoscopy in unstable patients—this delays definitive CTA localization and potential embolization. 1

• Do not assume bright red blood per rectum is always a lower GI source—up to 15% may be from an upper GI bleed. 1

• Do not perform colonoscopy without adequate bowel preparation—poor preparation leads to missed lesions and need for repeat procedures. 1

• Do not use fresh frozen plasma as first-line reversal for warfarin—PCC is faster, does not require ABO matching, and avoids volume overload. 1

• Never proceed to surgery without attempting radiologic localization first—blind resection has dramatically higher rebleeding and mortality rates. 1

Mortality Context

• Overall in-hospital mortality for lower GI bleeding is 3.4%, rising to 20% in patients requiring ≥4 units of red blood cells. 1

• Mortality is generally related to comorbidity rather than exsanguination. 1

• Emergency total colectomy mortality ranges from 27–33% versus ~10% when bleeding is first localized. 1