Lower Gastrointestinal Hemorrhage

New dedicated page — genuinely new topic for the wiki, not previously covered as a distinct entity. Content below is from a single textbook reference chapter (ASCRS Ch40 - Lower GI Hemorrhage), not primary literature.

Definition and epidemiology

Bleeding from a source distal to the ligament of Treitz. Comprises 30–40% of all GI bleeds and is the most common cause of GI-disease-related hospitalization in the US (800,000 annual admissions, $5 billion cost); the incidence has increased ~22% between 2000–2009, likely reflecting an aging population and rising anticoagulant use — the incidence of upper GI bleeds is meanwhile decreasing. Acute colonic bleeding has an annual incidence of ~36/100,000. Overall mortality from LGIB is reported as 1.3–3.9%; most mortality relates to patient comorbidities rather than uncontrolled bleeding itself, which is rarely fatal. Roughly 15% of patients presenting with apparent hematochezia actually have an upper GI source. The elderly carry disproportionate risk — LGIB incidence is >200-fold higher in patients over 80 than those age 20, reflecting a higher incidence of diverticulosis and angiodysplasia with age; in a large French study, 75% of LGIB patients had a predisposing medication (anticoagulant/antiplatelet).

Etiology

Diverticulosis is the most common cause overall and the most likely etiology for severe acute hemorrhage — diverticula develop at weak points in the colonic wall where penetrating vasa recta create a thin-walled sac closely apposed to the mucosa, a point of vulnerability to vascular erosion. Sigmoid/descending colon diverticulosis is present in 50% of the population, with a cumulative bleeding incidence of 2% at 5 years and 10% at 10 years (see Diverticulitis for this wiki's fuller diverticular-disease content, which is inflammation-focused rather than bleeding-focused). Anorectal disease is the second most common cause, most often hemorrhoids and anal fissures.

Presentation

Highly variable given the diversity of causes. Acute LGIB presents with sudden-onset hematochezia and/or melena, possibly with hemodynamic instability; chronic LGIB presents with longer-duration slow blood loss causing iron deficiency anemia and/or a positive fecal occult blood test. Melena suggests slower upper GI bleeding sources (oxidized heme transiting the lower GI tract), so a melena presentation should prompt investigation of an upper GI source first — but a brisk upper GI bleed can transit too quickly to convert to melena, so hematochezia with hemodynamic instability can still reflect an upper GI source and typically warrants NGT lavage and/or endoscopic evaluation to rule this out.

Evaluation

A focused history and physical exam should be performed in all patients presenting acutely, with assessment of hemodynamic stability as the top priority. History should focus on bleeding color/ amount/frequency/duration; associated symptoms (constipation, obstipation, bowel habit change, weight loss — raising malignancy concern); family history (malignancy risk); medication history (anticoagulants, NSAIDs, antiplatelet therapy); comorbid cardiopulmonary/renal/hepatic disease (affects both risk and management); and liver disease/alcohol history (portal hypertension raises suspicion for an upper GI variceal source).

Initial assessment: vital signs (including postural changes), abdominal exam, digital rectal exam. Nasogastric lavage can quickly rule out a gastric source. Anoscopy or an anorectal exam is mandatory to rule out a hemorrhoidal source (accounts for <20% of presentations); if anoscopy shows no obvious stigmata, further evaluation is needed. Hemodynamic instability from hemorrhoidal bleeding specifically is rare — other sources should be sought in an unstable patient with apparent hemorrhoidal bleeding.

Risk stratification

Important for triaging severity and guiding site-of-care decisions (inpatient vs. outpatient management of the stable patient). Risk stratification models for LGIB are less well developed than for upper GI bleeds, and existing models are not well designed to predict outpatient-management outcomes or limited in predicting poor outcomes generally. Risk factors associated with severe bleeding/poor outcomes: hemodynamic instability, ongoing bleeding, comorbid conditions, age >60, history of diverticulosis/angioectasia, elevated creatinine, and anemia — risk increases with the number of risk factors present. One study (Velayos et al.) found 79% of patients with all three of hemodynamic instability persisting >1 hour, hematocrit <35%, and active gross rectal bleeding had recurrent/ongoing bleeding.

• Shock index (SI) — heart rate ÷ systolic BP; SI >1 is classified as unstable and predictive of active bleeding; increasing SI is associated with mortality and can predict active extravasation on imaging.
• Oakland score — the only risk stratification score specifically designed and externally validated for LGIB (though only validated in the UK, and may underreport patients who could safely be discharged). Seven variables: age, gender, prior LGIB hospital admission, digital rectal exam findings, heart rate, systolic blood pressure, hemoglobin. Score ≤8 predicts a 95% probability of safe discharge/outpatient management.
• Other named scores: BLEED (inpatient morbidity), NOBLADS (bleeding risk — NSAIDs, diarrhea, abdominal tenderness, SBP ≤100, antiplatelet therapy, albumin <3.0, Charlson comorbidity >2, syncope), Sengupta (30-day mortality), Strate (bleeding severity). An artificial neural network model (Das et al.) predicted death/rebleed/intervention risk with a 98% negative predictive value when externally validated, but its advanced software/data-entry requirements have limited clinical adoption — risk stratification currently remains highly dependent on clinical judgment.

Management

80% of LGIB resolves spontaneously. The initial priority is severity assessment via the risk stratification tools above, combined with clinical judgment, to determine whether a patient can be managed as an outpatient (e.g., chronic LGIB with anemia and hemodynamic stability) or needs inpatient resuscitation.

Resuscitative targets: data specifically from LGIB RCTs is lacking (these trials generally excluded LGIB); practice extrapolates from severe upper GI bleed management — transfuse packed red blood cells to maintain hemoglobin 9 g/dL in patients with clinically significant comorbidity (e.g. cardiovascular disease) or 7 g/dL otherwise. No demonstrated difference between colloid and crystalloid resuscitation. In the upper GI bleed literature, IV fluid resuscitation is associated with decreased morbidity/mortality.

Anticoagulation management: in this aging population with increasing anticoagulant use, it's important to assess and reverse coagulopathy when appropriate, balanced against thromboembolic risk — communication with the specialist managing anticoagulation is important in stable patients. American College of Gastroenterology guidance (based on very-low-quality evidence) recommends reversal agents for INR >2.5; INR >1.5 has been shown to predict mortality but not rebleeding (observed mortality increase may reflect underlying comorbidity rather than the INR itself). Platelet transfusion is generally recommended for platelets <50×10⁹/L. Target-specific oral anticoagulants (rivaroxaban, dabigatran, apixaban) are especially challenging to manage — a meta-analysis of 43 RCTs found an OR of 1.45 (95% CI 1.07–1.97) for bleeding risk with these agents; their variable half-lives (5–19 hours) complicate management since clotting panels don't reflect the degree of anticoagulation. Nonspecific reversal agents (activated prothrombin complex concentrate) can be used; no high-level evidence exists on optimal reversal agent choice specifically for GI bleeds. Hematology consultation is recommended for severe life-threatening bleeding on oral anticoagulants.

Endoscopic evaluation and intervention

Endoscopy is often the preferred initial diagnostic modality — it uniquely combines source identification with therapeutic potential. In hemodynamically unstable patients with hematochezia, upper endoscopy should be performed in addition to colonoscopy. Colonoscopic diagnostic yield ranges 42–90%.

Technique: water-jet irrigation and a large working channel facilitate clearing food/clot; attempt irrigation of residual blood/stool, and intubate the terminal ileum to rule out a small bowel source. Bowel preparation is recommended when feasible for adequate visualization. Optimal timing isn't well defined: one RCT of urgent colonoscopy (<8 hours from presentation) vs. standard timing (next available) found significantly improved definitive-diagnosis rate with early colonoscopy (42% vs. 22%, OR 2.6) but no difference in rebleeding, surgery, or mortality; a separate RCT (Lain et al., 72 patients) comparing colonoscopy within 12 hours vs. delayed (30–60 hours) found no difference in rebleeding, diagnosis, or need for therapy. A meta-analysis reported improved therapeutic/diagnostic yield and length of stay with early colonoscopy, and the American College of Gastroenterology recommends colonoscopy within 24 hours in high-risk patients — while noting this recommendation is not associated with improved clinical outcomes or decreased likelihood of surgical intervention.

High-risk stigmata warranting endoscopic intervention: active bleeding, a non-bleeding visible vessel, and/or adherent clot — these findings predict a high rate of bleeding recurrence if no intervention is performed. Reported adverse event rates for endoscopic hemostasis techniques are low (as low as 0.3–1.3%). Modalities: injection, contact and non-contact thermal coagulation, topical sprays/powders, and mechanical therapies (clips) — can be combined as combination therapy, deemed safe. CO2 insufflation (rather than air) is advised to avoid perforation during long procedures. Endoscopic hemostasis has the highest benefit for diverticulosis, angioectasias, and post-polypectomy bleeds; LGIB from ischemic colitis, IBD, and colorectal neoplasms is generally not amenable to durable endoscopic hemostasis, though endoscopic diagnosis is still highly effective in guiding focused surgical/multimodal therapy for these etiologies.

• Diverticular bleeding: intervention indicated when active bleeding or a non-bleeding visible vessel/adherent clot is seen. A pooled analysis of 847 patients (Strate) found 80% successful hemostasis with 8% early and 12% late rebleeding; no advantage of combination therapy over monotherapy. Clips are preferred to cautery given the thin diverticular wall's delayed-perforation risk with thermal treatment. Epinephrine injection for local vasoconstriction can slow active bleeding ahead of clipping; the clip can be applied to the bleeding vessel or to close the diverticulum itself (tamponade). A translucent cap and/or injections can help evert the diverticulum for more precise localization/treatment; left-sided endoscopic banding (analogous to variceal banding) has also been described as successful. India ink tattoo at the intervention site aids future localization if rebleeding occurs.
• Angioectasia (also called angiodysplasia or arteriovenous malformations): more common in the elderly (>70) and the right colon. Risk factors for bleeding: multiple comorbidities, multiple lesions, anticoagulant/antiplatelet use. Argon plasma coagulation (APC) is the treatment of choice given ease of use, safety, and reduction of transfusion needs. In patients with Heyde syndrome (bleeding angioectasias + aortic stenosis), aortic valve replacement should also be considered.
• Post-polypectomy bleeding: endoscopic treatment success rate 95–100%. Risk factors: polyp size

  2cm, thick stalk, right-colon resection site, anticoagulation therapy; occurs in 0.6–9.7% of polypectomies. Endoscopic clips are the preferred modality across all these etiologies where possible, to avoid further tissue damage from energy-based therapies.

Radiologic evaluation

CT angiography (CTA): a highly effective early diagnostic modality; a three-phase protocol (non-contrast, arterial, venous) is recommended. 85.2% sensitivity/92.1% specificity for acute GI bleeding; the critical finding is active extravasation of contrast into the bowel lumen. Detectable bleeding rates: 0.25–3 mL/min with 79–100% sensitivity/50–100% specificity depending on phase protocol. A negative CTA in a hemodynamically stable patient is a good prognostic indicator (one review: 77.4% of 62 patients with negative CTA didn't rebleed). A shock index ≥1 can help select patients most likely to benefit from CTA. Given the ubiquity of CT, CTA can serve as an initial localizing modality generally.

Catheter-based angiography: the sole radiographic modality offering both localization and therapeutic treatment. Requires a bleeding rate >0.5 mL/minute and continuous bleeding to succeed; higher localization success in hemodynamically unstable patients (>5 units blood in 24h, SBP <90). A negative angiogram after a positive CTA is common. Provocative angiography (heparin, nitroglycerin, urokinase, or tPA) can increase localization likelihood at experienced centers but risks uncontrolled bleeding. Super-selective embolization (arteries <1mm, using microcoils, absorbable gelatin sponges, cyanoacrylate glue, or ethylene vinyl/polyvinyl) has 73–100% technical success and 63–96% clinical success, with rebleeding 11–50%. Self-limited ischemic bowel injury post-angiography is common; major ischemic complications occur in <3% of cases. A negative CTA usually obviates the need for angiography and scintigraphy, per an algorithm comparing early colonoscopy to a more conservative scintigraphy/angiography-then-colonoscopy pathway (underpowered RCT, no outcome difference, but colonoscopy had higher definitive-diagnosis rate: 42% vs. 22%).

Nuclear medicine/scintigraphy: historically the gold standard for localization given extreme sensitivity (technetium-99m-labeled RBC scintigraphy can detect bleeding as slow as 0.04–0.05 mL/minute — superior to ⁹⁹ᵐTc-sulfur colloid). Limitations: debated localization precision, no therapeutic capability, requires relative patient stability (time needed to radiolabel cells), incorrect localization in 10–25% of cases (risking inaccurate surgical treatment), and a 55% false-negative rate. RBC scintigraphy can detect bleeding for up to 24 hours and can be re-scanned if the initial scan is negative; sulfur colloid scanning allows immediate use (no autologous radiolabeling needed) but has a shorter half-life and can't be re-imaged later. Some evidence suggests CTA is now the preferred initial localization modality ahead of angiography, though other studies suggest scintigraphy-before-angiography allows more selective contrast injection.

Recurrent LGIB

Early rebleeding (before hospital discharge) occurs in 22% of cases; late rebleeding (after discharge) in 16%. Recurrent readmission rates: 13.7% at 14 days, 19% at 1 year. Risk factors: anticoagulation, multiple comorbidities, malignancy, non-aspirin antiplatelet agents, dual antiplatelet therapy, age >65, diverticulosis as the index bleeding source, and the initial hemostasis modality used. Repeat endoscopic evaluation is indicated in patients with recurrent LGIB and has a diagnostic yield of 3–60%. If bleeding can't be controlled endoscopically and the location is known, angiography/embolization should be considered. Recurrent LGIB without a prior localization poses a genuine clinical challenge — repeat upper/lower endoscopy has a 40–65% diagnostic yield; continued bleeding without endoscopic localization should prompt evaluation for a small bowel source. Surgical intervention absent a known bleeding location should be avoided (see Surgery below).

Small bowel / obscure GI bleeding

Obscure GI bleeding = bleeding from an unlocalized source after endoscopic/imaging evaluation; commonly termed "suspected small bowel bleeding" since most obscure sources originate there. Common small bowel etiologies: IBD, angioectasia, neoplasms, NSAID-induced ulcers, Dieulafoy's lesions. Should be considered only after second-look endoscopy rules out upper and lower GI sources (ileum evaluated on colonoscopy, distal duodenum/jejunum evaluated via push enteroscopy on EGD). Small bowel bleeding usually presents as stable occult bleeding.

• Capsule endoscopy (CE): a swallowed video-recording capsule transmitting wireless video of its transit. Diagnostic yield 38–83%; allows noninvasive full-small-bowel evaluation in 70–90% of patients; can change management in 37–87% of patients; high positive (94–97%) and negative (83–100%) predictive values. Positive findings are more likely with hemoglobin <10 g/dL, bleeding duration >6 months, more than one bleeding episode, overt bleeding, and CE performed within 2 weeks of the bleeding episode. Main drawbacks: no therapeutic capability, difficult precise localization. A repeat CE can be diagnostic in occult bleeding with a hemoglobin drop >4 g/dL. Multiple studies show CE superior to enteroscopy for small bowel bleeding evaluation generally.
• Enteroscopy: double balloon enteroscopy (DBE) evaluates ~240–360cm of bowel distal to the pylorus, offering both diagnostic and therapeutic capability (advantageous vs. CE) — diagnostic yield 60–80%, therapeutic intervention yield 40–73%; limited by invasiveness, prolonged intubation time, and specialized personnel needs; complication rate (incl. perforation, pancreatitis) ~1.2%. Single balloon enteroscopy (SBE, no balloon at the endoscope tip) has similar/ equivalent yield to DBE. CE before DBE is encouraged to minimize invasive-procedure use in low-probability patients, though CE can be falsely negative in high-suspicion patients, in which case enteroscopy may still be needed to rule out a small bowel etiology.
• Intraoperative enteroscopy: evaluation of the small bowel during laparotomy/laparoscopy, performed transorally, transrectally, and/or through an enterotomy. Diagnostic yield 50–88%, rebleeding rate 60%.

Surgery

Rarely required — surgical resection stops LGIB in only 7–25% of patients requiring it, and lower GI bleeding is, per the source chapter's own framing, "rarely a surgical disease." Surgical consultation should be obtained when radiologic/endoscopic localization and/or treatment attempts fail, and considered proactively in hemodynamically unstable patients so surgeons can participate in decision-making. Localization/diagnosis is critical before surgery, since inflammatory bowel disease and malignancy can markedly change operative strategy/approach; oncologic resection should be attempted when possible for colonic/small bowel malignancy causing ongoing hemorrhage, and radiation therapy may be part of the treatment paradigm for imminent bleeding control in rectal cancer.

Non-localized LGIB (small bowel source ruled out, anoscopy negative, terminal ileal intubation negative for blood): subtotal colectomy should be considered when surgery can't be avoided. The preferred initial approach for totally non-localized bleeding is diagnostic laparoscopy and/or exploratory laparotomy running the bowel in its entirety, with intraoperative colonoscopy/enteroscopy options if no lesion is found. A blind subtotal colectomy can be considered if no source is identified despite colonoscopy/enteroscopy and a colonic origin is suspected; in relatively stable patients, a temporary loop ileostomy may afford the opportunity to better distinguish a small vs. large bowel source postoperatively. Rebleeding after blind subtotal colectomy is ~4%.

Segmental resection is preferred when the bleeding source has been confidently identified, given improved bowel function vs. subtotal colectomy; segmental colectomy bleeding rates are 4–14% (reflecting incomplete localization risk). Subtotal colectomy is reserved for uncertain colonic source. Whether to create a stoma with subtotal colectomy depends on the patient's hemodynamics.

Related pages

• Diverticulitis — this wiki's existing diverticular-disease coverage, which is inflammation/management-focused; this page adds the bleeding-specific presentation of diverticular disease.
• Large Bowel Obstruction and Volvulus — the other major acute colorectal-emergency condition pages sourced from the same textbook run (Chapters 38–39).
• Anastomotic Construction — general segmental-resection/anastomosis technique referenced above for surgical management of localized bleeding.

Open items / gaps

• All content is from a single textbook reference chapter — no primary literature independently ingested yet. Highest-value candidates for future ingestion, given how heavily this page leans on them: the Oakland score validation study (the only LGIB-specific externally-validated risk score), the Strate diverticular-bleeding pooled analysis (847 patients), and the urgent-vs.- standard colonoscopy-timing RCT.
• No data yet in this wiki on how this chapter's anticoagulation-reversal guidance interacts with perioperative anticoagulation management more broadly — worth cross-checking against Preoperative Evaluation & Perioperative Risk Optimization once that overlap is examined closely.
• The chapter's own risk-stratification section notes models are "not well designed" for predicting poor outcomes or guiding outpatient management — this limitation is stated but not resolved by the chapter, and isn't resolved here either.
• Fig. 40.9's full treatment algorithm is described in prose above but not reproduced as a diagram — worth doing if/when this wiki adopts a diagramming convention for algorithms.