Gastrointestinal & Hepatic · Topic 3 of 26

Lower GI Bleeding

Gastrointestinal · GI bleeding

Lower GI Bleeding

Usually diverticular and usually self-limited. Unstable and still bleeding: CT angiography, then embolization. Stable: a prepped, nonurgent colonoscopy.

Key numbers

Transfuse RBCs below hemoglobin 7 g/dLHgb < 7 (8 with CVD)

Colonoscopy after prep, not urgentlyNo benefit < 24 h

Positive CTA: angiography and embolization promptlyAngiography ≤ 90 min

Oakland score 8 or less: early dischargeOakland ≤ 8

01 · FirstOngoing unstable hematochezia: CT angiography first

For ongoing, hemodynamically significant hematochezia, order CT angiography as the first test; it localizes active bleeding (sensitivity about 90%) but has low yield once bleeding has stopped.

02 · DoTransfuse RBCs below hemoglobin 7 g/dL

Use a restrictive transfusion threshold of hemoglobin 7 g/dL in hemodynamically stable patients; consider 8 g/dL with cardiovascular disease or acute coronary syndrome.

03 · FirstColonoscopy after prep, not urgently

Admitted patients who need colonoscopy get a nonemergent inpatient colonoscopy after bowel preparation; colonoscopy within 24 hours does not reduce rebleeding or mortality.

Causes & risk factors

Why it happens

Diverticular bleeding: painless hematochezia, usually stops must knowDiverticular bleeding is the most common cause of acute lower GI bleeding (30–65%): sudden, painless, often large-volume hematochezia from a vasa recta arteriole that stops spontaneously in most patients.

Angiodysplasia: older adults, cecum and ascending colonAngiodysplasias cluster in the cecum and ascending colon of adults over 60, with links to kidney failure, aortic stenosis and cirrhosis; bleeding is painless, intermittent and rarely massive (heme-positive stool or modest hematochezia).

Diagnosis & monitoring

Work-up

Oakland score 8 or less: early dischargeThe Oakland score (age, sex, prior LGIB, rectal exam, heart rate, systolic BP, hemoglobin) of 8 or less identifies low-risk patients for early discharge and outpatient evaluation, supplementing clinical judgment.

Do right now

In this order

First moves

Resuscitate before any endoscopic evaluation

→

Transfuse RBCs below hemoglobin 7 g/dLHgb < 7 (8 with CVD)

→

Unstable hematochezia: exclude an upper source

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Ongoing unstable hematochezia: CT angiography first

→

Positive CTA: angiography and embolization promptlyAngiography ≤ 90 min

Why each step

Resuscitate before any endoscopic evaluationPatients with hemodynamic instability or suspected ongoing bleeding receive IV fluid resuscitation, aiming to normalize blood pressure and heart rate before endoscopic evaluation or intervention.

Transfuse RBCs below hemoglobin 7 g/dLUse a restrictive transfusion threshold of hemoglobin 7 g/dL in hemodynamically stable patients; consider 8 g/dL with cardiovascular disease or acute coronary syndrome.

Unstable hematochezia: exclude an upper sourceHematochezia with hemodynamic instability may come from a brisk upper GI source; perform upper endoscopy first when history and laboratory findings (for example, liver disease) make an upper source likely.

Ongoing unstable hematochezia: CT angiography firstFor ongoing, hemodynamically significant hematochezia, order CT angiography as the first test; it localizes active bleeding (sensitivity about 90%) but has low yield once bleeding has stopped.

Positive CTA: angiography and embolization promptlyRefer a CTA showing extravasation promptly to interventional radiology: catheter angiography within 90 minutes is 9 times more likely to find the bleeder, and superselective embolization succeeds in about 98%.

Management

Orders

Treat diverticular stigmata with clips or bandsWhen colonoscopy shows stigmata of recent hemorrhage in a diverticulum (active bleeding, visible vessel, adherent clot), treat with through-the-scope clips, band ligation or coagulation.

Warfarin: reverse only life-threatening bleeds, with PCCMost LGIB on warfarin needs no reversal; for life-threatening bleeding with an INR well above range, 4-factor prothrombin complex concentrate is preferred over fresh frozen plasma because it lowers INR faster.

DOAC reversal only for life-threatening bleedingReverse a DOAC only for life-threatening bleeding that persists despite resuscitation and stopping the drug, taken within about 24 hours: idarucizumab for dabigatran, 4-factor PCC for apixaban or rivaroxaban.

Continue cardiac aspirin; hold other antiplateletsContinue aspirin taken for secondary cardiovascular prevention during the admission if possible; hold nonaspirin antiplatelet agents initially when hematochezia is severe.

Resume anticoagulation once bleeding stopsRestart anticoagulation after the bleeding has stopped: resumption lowers post-bleed thromboembolism and mortality (strong recommendation).

Surgery when other therapy fails; localize firstSurgery is reserved for continued bleeding (for example, more than 6 units transfused) despite endoscopic and angiographic therapy; localize the source first — if it cannot be found, subtotal colectomy rather than blind hemicolectomy.

Red flags & don'ts

Avoid harm

No tranexamic acid for lower GI bleeding avoidDo not give tranexamic acid or other antifibrinolytics for lower GI bleeding (strong recommendation): no outcome benefit, and HALT-IT showed more venous thromboembolism.

Diverticular bleed or angiodysplasia?

Commonly confused

Presentation	Sudden painless large-volume hematochezia
Typical patient	Older adult with diverticulosis; NSAID or aspirin use
Location	Any colonic diverticulum
Endoscopic therapy	Clips, band ligation or coagulation

More detail

Reference

Show 5 reference facts

Embolization causes bowel ischemia or ulceration in about 5%; even after embolization, 30-day rebleeding is about 16% and mortality about 13%.

About 80% of patients with a negative CT angiogram have no rebleeding and need no further urgent evaluation.

Inpatient colonoscopy uses 4–6 L of polyethylene glycol (split or low-volume preparations acceptable); unprepped examination or routine flexible sigmoidoscopy is not recommended unless the source is anorectal or distal.

NSAIDs and aspirin raise the risk of lower GI and diverticular bleeding; after a diverticular bleed, rebleeding is 17–33% early and 26–32% late.

Other causes of lower GI bleeding: ischemic colitis, hemorrhoids, colorectal neoplasia, postpolypectomy bleeding, inflammatory, infectious or radiation colitis, and NSAID or stercoral ulcers.

Pearl

Painless, brisk hematochezia in an older adult is diverticular until proven otherwise — and it usually stops on its own.

Sources · Sengupta N et al. Management of Patients With Acute Lower Gastrointestinal Bleeding: An Updated ACG Guideline. Am J Gastroenterol 2023;118:208–231 · Management of Acute Lower GI Bleeding: Guidelines From the ACG (Practice Guidelines). Am Fam Physician 2024;109:284–285 · Merck Manual Professional — Overview of Gastrointestinal Bleeding (updated Nov 2025) · Merck Manual Professional — Colonic Diverticulosis (updated Jun 2026) · Merck Manual Professional — Vascular Gastrointestinal Lesions · HALT-IT Trial Collaborators. High-dose 24-h tranexamic acid in acute gastrointestinal bleeding. Lancet 2020;395:1927–36 · TCTMD — Andexanet alfa pulled from the US market (Dec 2025) · Abraham NS et al. ACG–CAG Clinical Practice Guideline: Management of Anticoagulants and Antiplatelets During Acute GI Bleeding and the Periendoscopic Period. Am J Gastroenterol 2022 · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).