Residency · Residency · Gastroenterology

Lower GI Bleeding - Evaluation and Management

Definition and Epidemiology

Lower gastrointestinal bleeding is defined as hemorrhage originating distal to the ligament of Treitz. The incidence is approximately 20 to 30 per 100,000 per year and increases dramatically with age, with a 200-fold increase from the third to the ninth decade of life. Overall mortality is 2 to 4%, which is lower than that of upper GI bleeding. An important characteristic of lower GI bleeding is that 80 to 85% of episodes stop spontaneously, though the recurrence rate after an initial episode is 10 to 20%.

Etiology

Common Causes (by frequency in adults)

Diverticular bleeding is the most common cause of significant lower GI bleeding, accounting for 30 to 40% of cases. It characteristically presents as painless, massive, and often self-limited hemorrhage. Despite the predominance of diverticula in the left colon, diverticular bleeding more commonly originates from right-sided (ascending colon) diverticula, where the vasa recta are exposed over a larger dome area. Angiodysplasia and arteriovenous malformations account for 5 to 15% of cases and consist of thin-walled ectatic vessels that are predominantly located in the right colon. Angiodysplasia is associated with aortic stenosis (Heyde syndrome), chronic kidney disease, and von Willebrand disease.

Hemorrhoids are the most common cause of hematochezia overall but rarely cause significant lower GI bleeding, accounting for 5 to 10% of cases evaluated for acute hemorrhage. Colonic neoplasms and polyps contribute 5 to 10% of cases and typically present with chronic occult bleeding rather than acute hemorrhage; post-polypectomy bleeding occurs in 0.5 to 2% of polypectomies. Various forms of colitis, including inflammatory bowel disease, ischemic colitis, infectious colitis, and radiation colitis or proctitis, collectively account for 5 to 10% of cases. Anorectal pathology beyond hemorrhoids includes fissures, rectal varices, solitary rectal ulcer, and Dieulafoy lesions. Post-procedural bleeding, whether following polypectomy, biopsy, or endoscopic mucosal resection or submucosal dissection, may occur immediately or be delayed for up to 30 days. Importantly, 5 to 10% of presumed lower GI bleeding actually originates from small bowel sources, including angioectasias, Crohn disease, Meckel diverticulum, and small bowel tumors.

Ischemic Colitis

Ischemic colitis preferentially affects the watershed areas of the colon, specifically the splenic flexure at Griffiths point and the rectosigmoid junction at Sudeck point. Risk factors include age over 60, atherosclerosis, low-flow states, vasoconstrictors, cocaine use, and marathon running. The classic presentation is sudden crampy left lower quadrant pain followed by bloody diarrhea within 24 hours. CT imaging reveals colonic wall thickening, thumbprinting, and a segmental distribution. Colonoscopy demonstrates edema, submucosal hemorrhage, blue-black mucosa, and ulceration, with rectal sparing being typical because the rectum receives its blood supply from the superior rectal artery arising from the inferior mesenteric artery. Management is primarily supportive, consisting of bowel rest, intravenous fluids, and broad-spectrum antibiotics in severe cases, with surgical intervention reserved for gangrene, perforation, or peritonitis.

Initial Assessment

Distinguishing UGIB from LGIB

A critical initial step in evaluating a patient with hematochezia is distinguishing a lower GI source from an upper GI source, as 10 to 15% of patients presenting with hematochezia have a brisk upper GI bleed as the etiology. The presence of hemodynamic instability with hematochezia should raise suspicion for an upper source. A BUN-to-creatinine ratio exceeding 30 also suggests an upper source due to the absorption of hemoglobin in the upper gastrointestinal tract. Nasogastric aspirate can be informative: bile without blood suggests a lower source, bloody aspirate confirms an upper source, but non-bile, non-bloody aspirate is non-diagnostic. When there is clinical suspicion for an upper source, upper endoscopy should be performed first.

Hemodynamic Assessment and Resuscitation

Resuscitation principles mirror those for upper GI bleeding, including establishing 2 large-bore intravenous lines, initiating crystalloid resuscitation, and following a restrictive transfusion strategy with a hemoglobin threshold of 7 g/dL unless the patient is actively exsanguinating or has high cardiac risk. Early type and screen or crossmatch is essential.

Risk Stratification

The Oakland Score is a validated risk stratification tool that incorporates age, sex, prior lower GI bleeding admission, digital rectal examination findings, heart rate, systolic blood pressure, and hemoglobin level. A score of 8 or less identifies patients who can safely be managed as outpatients, with 95% sensitivity for safe discharge. Additional factors that predict adverse outcomes include hemodynamic instability, anticoagulant use, more than 2 comorbidities, and prolonged bleeding.

<image>A clinical decision algorithm for acute lower GI bleeding management. Begin at top with "Acute hematochezia." First decision: "Hemodynamically stable?" If no: "Resuscitate, consider UGIB source, upper endoscopy if suspected." If yes: "Risk stratify with Oakland Score." Score <=8: "Outpatient evaluation with elective colonoscopy." Score >8: "Admit, prep, colonoscopy within 24 hours." After colonoscopy, branch to: "Source identified" (leading to endoscopic therapy options: clips, thermal, injection, band ligation) and "Source NOT identified" (leading to: "Ongoing bleeding?" If yes: CT angiography, then "Active extravasation?" leading to IR embolization or tagged RBC scan. If no ongoing bleeding: "Consider upper endoscopy, capsule endoscopy, repeat colonoscopy"). Side pathway for "Massive/life-threatening bleeding" going directly to CT angiography and/or IR/surgery. Use red for emergent pathways, yellow for urgent, green for elective/outpatient. Include Oakland Score components in a side box.</image>

Diagnostic Approach

Colonoscopy

Colonoscopy is the gold standard for evaluating lower GI bleeding, achieving a diagnostic yield of 74 to 100%. The recommended timing is within 24 hours of presentation, following rapid bowel preparation. Current ACG 2023 guidelines recommend colonoscopy within 24 hours for most patients but do not advocate for emergent colonoscopy within 12 hours, as the Strate meta-analysis demonstrated that early colonoscopy increases diagnostic yield and intervention rate but does not reduce mortality, rebleeding, or the need for surgery. Bowel preparation is essential for achieving adequate diagnostic yield and requires 4 to 6 liters of polyethylene glycol solution administered over 3 to 4 hours, with a nasogastric tube placed if the patient is unable to drink. Sodium phosphate preparations should be avoided due to nephrotoxicity. Unprepared or emergent colonoscopy generally has poor visualization and low diagnostic yield and is not recommended unless massive ongoing bleeding prevents adequate preparation.

CT Angiography (CTA)

CT angiography can detect active bleeding at rates of 0.3 to 0.5 mL per minute or greater, with a sensitivity of 79 to 95% and specificity of 95 to 100% for active extravasation. Its advantages include rapid availability, ability to localize the bleeding source for targeted interventional radiology, and capacity to identify non-GI sources of bleeding. CTA should be obtained before a tagged red blood cell scan when interventional radiology intervention is anticipated. A three-phase protocol consisting of non-contrast, arterial, and delayed venous phases is standard. The "spot sign," defined as contrast extravasation that increases between arterial and delayed phases, indicates active hemorrhage.

Tagged Red Blood Cell Scan (99mTc-RBC scintigraphy)

Tagged red blood cell scintigraphy can detect bleeding at rates of 0.1 to 0.4 mL per minute, making it more sensitive than CTA, though with less specific anatomic localization. It is particularly useful for intermittent slow bleeding when CTA is negative, as imaging can be performed over a 24-hour period. A positive scan guides subsequent angiographic intervention. The primary limitation is poor anatomic localization, particularly in the transverse colon, which is redundant and mobile.

Catheter Angiography

Catheter angiography detects bleeding at rates of 0.5 to 1.0 mL per minute or greater and offers the advantage of therapeutic capability through embolization when a bleeding source is identified. Superselective embolization is performed using microcoils, gelatin sponge (Gelfoam), or polyvinyl alcohol particles. Ischemic complications occur in 0 to 4% of cases with superselective technique. To maximize diagnostic yield, catheter angiography should be performed after a positive CTA to guide catheter positioning.

Capsule Endoscopy and Deep Enteroscopy

When upper and lower endoscopy fail to identify a bleeding source, video capsule endoscopy serves as the first-line investigation for suspected small bowel bleeding, with a diagnostic yield of 38 to 83%. Device-assisted enteroscopy using single-balloon, double-balloon, or spiral enteroscopy platforms allows tissue sampling and therapeutic intervention for lesions identified on capsule endoscopy.

Endoscopic Therapy for LGIB

Diverticular Bleeding

Endoscopic therapy for diverticular bleeding requires identification of an actively bleeding diverticulum or stigmata of recent hemorrhage such as a visible vessel or adherent clot. Treatment modalities include epinephrine injection at a 1:10,000 dilution into or around the bleeding point, mechanical hemostasis with through-the-scope or over-the-scope clips applied to the bleeding point or at the neck of the diverticulum, bipolar coagulation (with caution given the thin diverticular wall and associated perforation risk), and band ligation, which has increasing evidence supporting its efficacy for actively bleeding diverticula. Endoscopic tattoo marking of the bleeding diverticulum is important for surgical localization should endoscopic intervention fail.

Angiodysplasia

Argon plasma coagulation (APC) is the most commonly used modality for treating angiodysplasia, employing non-contact thermal energy at typical settings of 40 to 60 watts and 1 to 2 liters per minute flow. Bipolar coagulation, clips, and band ligation are alternatives for larger lesions. For recurrent or multifocal angiodysplasia, medical therapy options include octreotide at 100 to 200 mcg subcutaneously three times daily or as a long-acting release formulation at 20 mg monthly (off-label), thalidomide at 100 mg daily (supported by small trials), and tranexamic acid.

Post-Polypectomy Bleeding

Immediate post-polypectomy bleeding is managed with clips, thermal coagulation, or injection. Delayed bleeding, which most commonly occurs 7 to 14 days after the procedure but may be delayed up to 30 days, requires repeat colonoscopy with clip or thermal therapy. Prevention strategies include prophylactic clip placement for large pedunculated polyps exceeding 2 cm or those with thick stalks, and use of a detachable snare (endoloop) for pedunculated polyps.

Radiation Proctitis

Argon plasma coagulation is the most commonly used treatment for radiation proctitis, typically requiring 2 to 4 sessions. Additional options include formalin application using 4% formalin-soaked gauze applied directly to telangiectasias, radiofrequency ablation using the HALO90 system as an emerging modality, sucralfate enemas at 2 g in 20 mL of water twice daily, and hyperbaric oxygen therapy for refractory cases, typically requiring 30 to 40 sessions.

<image>An endoscopic image panel showing four common LGIB sources and their endoscopic treatment. Panel 1 "Diverticular bleeding": endoscopic view of a colonic diverticulum with a visible vessel at its dome, alongside a second image showing a hemoclip deployed across the vessel at the diverticular neck. Panel 2 "Angiodysplasia": a bright red, flat, fern-like vascular lesion with radiating vessels in the cecum, alongside treatment with argon plasma coagulation showing the blue APC beam applied to the lesion with surrounding white coagulation effect. Panel 3 "Post-polypectomy bleeding": a polypectomy site with oozing from the stalk remnant, alongside clip closure of the defect. Panel 4 "Radiation proctitis": rectal mucosa with multiple telangiectasias and friable red spots, alongside APC treatment showing systematic coagulation of individual telangiectasias. Use realistic colonic mucosal tones (pink-tan) with appropriate vasculature and bleeding coloring. Label all relevant structures.</image>

Interventional Radiology

Transcatheter Arterial Embolization

Transcatheter arterial embolization is indicated for ongoing bleeding despite endoscopic therapy, massive bleeding that prevents colonoscopy, and CTA-positive extravasation. The procedure involves superselective catheterization of the bleeding vessel at the vasa recta level, with embolization agents including microcoils (most commonly used), gelatin sponge, polyvinyl alcohol particles, and n-butyl cyanoacrylate. Technical success rates are 85 to 95%, with clinical success rates of 60 to 85%. Rebleeding occurs in 15 to 25% of cases, and ischemic complications occur in 0 to 4% with superselective technique, with higher risk in the superior mesenteric artery territory.

Vasopressin Infusion

Vasopressin infusion has been largely replaced by embolization in modern practice. Historically, it was administered as an intra-arterial infusion at 0.2 to 0.4 units per minute. Its use is limited by complications including cardiac ischemia and mesenteric ischemia, as well as a rebleeding rate of approximately 50% after cessation of the infusion.

Surgical Management

Surgical intervention for lower GI bleeding is indicated for massive hemorrhage uncontrolled by endoscopy or interventional radiology, hemodynamic instability despite resuscitation, transfusion requirements exceeding 6 units of packed red blood cells in 24 hours, or recurrent bleeding after multiple interventions. Segmental colectomy is preferred when the bleeding source has been localized by endoscopy, CTA, or tagged red blood cell scan, as it carries lower morbidity and mortality than subtotal colectomy. When the bleeding source has not been localized, subtotal colectomy with ileorectal anastomosis is the recommended procedure, carrying a mortality of 10 to 25% but a lower rebleeding rate than blind segmental resection. Intraoperative enteroscopy may help localize the source before resection is performed.

Small Bowel (Mid-GI) Bleeding

Definition

Small bowel bleeding, previously termed "obscure GI bleeding," is now defined as hemorrhage originating between the ampulla of Vater and the ileocecal valve. It is classified as either overt (visible) or occult small bowel bleeding.

Approach

The diagnostic approach to suspected small bowel bleeding begins with video capsule endoscopy as the first-line investigation after negative bidirectional endoscopy, followed by device-assisted enteroscopy for biopsy and therapy of lesions identified on capsule study. CT enterography or MR enterography is appropriate for evaluating mass lesions and Crohn disease. A Meckel scan using technetium-99m pertechnetate is obtained for suspected Meckel diverticulum, primarily in young patients. Intraoperative enteroscopy serves as a last resort for recurrent, severe small bowel bleeding that has not been localized by other means.

Key Clinical Pearls

• 10-15% of hematochezia originates from an upper GI source — always consider UGIB in hemodynamically unstable patients with hematochezia
• Oakland Score <=8 identifies patients safe for outpatient management of LGIB
• Bowel preparation is essential for diagnostic colonoscopy in LGIB — unprepared exams have poor yield
• CT angiography should be obtained before catheter angiography to guide superselective embolization
• Diverticular bleeding is typically right-sided despite left-sided diverticular predominance
• Most LGIB (80-85%) stops spontaneously; the key challenge is identifying the source for definitive treatment
• For massive unlocalized LGIB requiring surgery, subtotal colectomy is preferred over blind segmental resection
• Angiodysplasia of the right colon associated with aortic stenosis (Heyde syndrome) involves acquired von Willebrand syndrome type IIA

References

1. Strate LL, et al. ACG Clinical Guideline: Management of Patients with Acute Lower Gastrointestinal Bleeding. Am J Gastroenterol. 2023;118(2):208-231.
2. Oakland K, et al. Diagnosis and management of acute lower gastrointestinal bleeding: guidelines from the British Society of Gastroenterology. Gut. 2019;68(5):776-789.
3. Laine L, et al. SCENIC International Consensus Statement on Surveillance and Management of Dysplasia in Inflammatory Bowel Disease. Gastroenterology. 2015;148(3):639-651.
4. Defined-LGIB: Nagata N, et al. Colonic diverticular bleeding: urgent colonoscopy vs wait-and-see approach. Gastroenterology. 2022;162(7):S122.
5. Green BT, Rockey DC. Lower gastrointestinal bleeding - management. Gastroenterol Clin North Am. 2005;34(4):665-678.

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