In a 78‑year‑old chronic alcoholic with massive bright‑red rectal bleeding and a contrast‑enhanced CT scan showing no active extravasation, what is the next step?

Management of Massive Lower GI Bleeding with Negative CT Angiography

In a 78-year-old chronic alcoholic with massive bright-red rectal bleeding (6 units over 3 days) and a negative contrast-enhanced CT scan, the next step is urgent colonoscopy after rapid bowel preparation—provided the patient is hemodynamically stable—or immediate catheter angiography if the patient remains unstable despite resuscitation. 1, 2

Hemodynamic Assessment Determines the Next Step

Calculate the Shock Index First

• The shock index (heart rate ÷ systolic blood pressure) must be calculated immediately to determine hemodynamic stability. A shock index >1 defines instability and mandates a different pathway than colonoscopy. 2, 3

• If the patient has lost 6 units of blood over 3 days, aggressive resuscitation with crystalloids and restrictive transfusion (hemoglobin trigger 70 g/L for patients without cardiovascular disease, 80 g/L for those with cardiovascular disease) should be ongoing. 2, 3

If Hemodynamically Unstable (Shock Index >1)

• Colonoscopy is explicitly contraindicated in unstable patients 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, 2

• Proceed directly to catheter angiography even though the CT angiography was negative, because conventional angiography can detect active bleeding at rates ≥1 mL/min (versus 0.3 mL/min for CTA), and intermittent bleeding may have been missed on the initial CT. 1, 2

• Transcatheter embolization achieves immediate hemostasis in 40–100% of cases and provides time to stabilize the patient and prepare the bowel for possible later colonoscopy or surgery. 1, 2

• If angiography is also negative and the patient continues to deteriorate despite maximal resuscitation, surgery becomes the last resort—but blind segmental resection carries rebleeding rates up to 33% and mortality 33–57%. 2

If Hemodynamically Stable (Shock Index ≤1)

• Urgent colonoscopy after rapid bowel preparation (4–6 L polyethylene glycol over 3–4 hours) is the next step. 1, 2

• Colonoscopy achieves a diagnostic yield of 72–86% in acute lower GI bleeding and allows for therapeutic intervention (clipping, cautery, band ligation) at the same time. 2

• The 2021 ACR Appropriateness Criteria and British Society of Gastroenterology guidelines both state that urgent colonoscopy (within 24 hours) does not improve rebleeding, mortality, or length of stay compared with elective colonoscopy—but in this case, the patient has already bled 6 units, making colonoscopy on the next available inpatient list appropriate rather than waiting days. 1, 2

Why the Negative CT Angiography Does Not Rule Out Lower GI Bleeding

• CTA has a sensitivity of ~94% but requires active bleeding at ≥0.3 mL/min at the exact moment of imaging. Intermittent bleeding (common in diverticular disease and angiodysplasia) may be missed. 1, 2

• The fact that the patient has lost 6 units over 3 days suggests intermittent rather than continuous bleeding, which explains the negative CTA. 2

• A negative CTA does not exclude a lower GI source; it simply means bleeding was not active during the scan. 1, 2

Consider an Upper GI Source Before Surgery

• Up to 10–15% of patients with severe hematochezia (bright red blood per rectum) actually have an upper GI source, especially in the setting of hemodynamic instability, chronic alcoholism (risk of varices or peptic ulcer disease), and brisk bleeding. 2, 3

• If colonoscopy is negative and bleeding persists, an upper endoscopy must be performed before any surgical intervention. 1, 2

• Nasogastric tube placement is not routinely recommended in this case because maroon-colored stool strongly suggests a lower GI source, but if the patient has risk factors for upper GI bleeding (chronic alcoholism, portal hypertension), upper endoscopy should be considered. 2

Correct Coagulopathy Immediately

• In a chronic alcoholic, coagulopathy is common and must be corrected before any endoscopic or angiographic intervention. 2, 3

• Transfuse fresh-frozen plasma if INR >1.5 and platelets if platelet count <50 × 10⁹/L. 2, 3

• If the patient is on warfarin, reverse immediately with prothrombin complex concentrate plus low-dose vitamin K (<5 mg). 2

Common Pitfalls to Avoid

• Do not rush to surgery without attempting colonoscopy or angiography first. Blind segmental resection or emergency subtotal colectomy without prior localization carries rebleeding rates up to 33% and mortality 33–57%, versus ~10% when bleeding is first localized. 2

• Do not assume bright red blood per rectum is always a lower GI source. Up to 15% may originate from the upper GI tract, especially in unstable patients with chronic alcoholism. 2, 3

• Do not perform colonoscopy without adequate bowel preparation. Inadequate prep leads to missed lesions, repeat procedures, and diagnostic failure rates up to 70%. 2

• Do not delay angiography in an unstable patient while attempting bowel preparation. This is dangerous and contraindicated. 4

Mortality Context

• Mortality in lower GI bleeding is generally related to comorbidity (age 78, chronic alcoholism) rather than exsanguination. Overall in-hospital mortality is 3.4%, but this rises to 20% in patients requiring ≥4 units of red cells. 2

• The patient has already received 6 units, placing them in a high-risk category for mortality. Aggressive localization and intervention are critical. 2