Gastrointestinal

Lower GI bleeding: workup and management

Clinical Overview and When to Suspect Lower GI Bleeding

— Incidence ~36/100,000 adults/year; rises sharply after age 65

— Mortality 2–4%, higher in elderly, hemodynamically unstable, and those bleeding while hospitalized for another reason

— ~80–85% of LGIB stops spontaneously

— Diverticulosis (~30–40%) — painless, abrupt, large-volume hematochezia in older adult on NSAIDs/antiplatelets

— Angioectasia/AVMs — recurrent, painless, often in CKD, aortic stenosis (Heyde), LVADs

— Ischemic colitis — older patient, crampy LLQ pain, then bloody diarrhea

— Hemorrhoids/anorectal — small-volume bright blood on tissue, common but a diagnosis of exclusion in older patients

— Neoplasia (colorectal cancer/polyps) — chronic occult or intermittent overt bleeding, anemia

— IBD, infectious colitis, radiation proctitis, post-polypectomy bleed (typically within 14 days)

— Hematochezia + hemodynamically stable + normal NG aspirate → LGIB likely

— Key distinction: brisk UGIB (e.g., variceal, ulcer with visible vessel) can present as hematochezia in ~10–15% of cases; tachycardia, orthostasis, or BUN/Cr >30 should push you toward upper source first

Board pearl: painless large-volume hematochezia in a 70-year-old on aspirin = diverticular bleed until proven otherwise; pain + bloody diarrhea = think ischemic colitis or infectious colitis instead.

Definition: Lower GI bleeding (LGIB) = bleeding distal to the ligament of Treitz, classically presenting as hematochezia (bright red or maroon stool) or, less commonly, melena from a slow right-colonic source.

Epidemiology and risk profile:

Most common etiologies in US adults (rough order):

When to suspect LGIB over UGIB:

Step 3 framing: the exam wants you to (1) resuscitate, (2) localize via NG lavage or upper endoscopy if unstable, (3) prepare colonoscopy after adequate prep, (4) escalate to CT angiography or interventional radiology if bleeding is brisk.

Presentation Patterns and Key History

— Bright red blood per rectum (BRBPR), mixed with stool → left colon/rectosigmoid

— Bright red blood coating stool or on tissue only → anorectal (hemorrhoids, fissure)

— Maroon stool/clots → right colon or brisk small bowel

— Melena → usually UGIB but slow right colon or cecal lesion can produce it

— Sudden painless large-volume bleed → diverticular or angioectasia

— Chronic intermittent scant bleeding + iron deficiency anemia → neoplasia (colon cancer until proven otherwise in age ≥45)

— Bloody diarrhea with urgency, tenesmus, weight loss → IBD

— Bloody diarrhea after antibiotics or recent travel → infectious colitis (C. diff, Shiga toxin E. coli, Shigella, Campylobacter)

— Crampy LLQ pain → ischemic colitis, esp. after AAA repair, hypotension, cocaine use, marathon running

— Painful defecation with bright streak → anal fissure (think constipation, hard stool)

— Weight loss, change in caliber, tenesmus → colorectal cancer

— Pulsatile abdominal mass or prior aortic graft → aortoenteric fistula (surgical emergency)

— NSAIDs, aspirin, P2Y12 inhibitors, DOACs, warfarin — both cause and prognostic risk factor

— SSRIs (platelet dysfunction)

— CKD, cirrhosis, aortic stenosis, LVAD → angioectasia

— Recent polypectomy (post-procedure bleed up to 14 days)

— Pelvic radiation history → radiation proctitis (often years later)

Step 3 management: in the outpatient setting, any patient ≥45 with new hematochezia — even if "looks like hemorrhoids" — needs colonoscopy to exclude malignancy; don't be reassured by visible external hemorrhoids alone. Document a digital rectal exam and anoscopy result before attributing bleeding to hemorrhoids.

Stool character — anchor of localization:

Tempo and volume:

Associated symptoms (high-yield triggers):

Medication and comorbidity history (always ask):

Social/family: family history of CRC or IBD, alcohol use, travel, sexual practices (proctitis).

Physical Exam Findings and Hemodynamic Assessment

— HR >100, SBP <90, orthostatic ΔSBP ≥20 or ΔHR ≥20 → significant volume loss (≥15% blood volume)

— Cool extremities, delayed cap refill, altered mentation → class III/IV shock

— Normal vitals in elderly on beta-blockers can be falsely reassuring — watch lactate and mentation

— Abdomen: tenderness suggests ischemic colitis, IBD, infection; peritoneal signs → perforation, transmural ischemia

— Pulsatile mass or bruit → AAA / aortoenteric fistula

— Stigmata of chronic liver disease (spider angiomata, splenomegaly, ascites) → consider variceal UGIB masquerading as LGIB

— Skin: telangiectasias on lips/tongue → hereditary hemorrhagic telangiectasia (HHT/Osler-Weber-Rendu)

— Conjunctival pallor, koilonychia → chronic blood loss

— Inspect for external hemorrhoids, fissure, fistula, mass

— DRE: palpate for masses, assess sphincter tone, note stool color on glove

— Anoscopy at bedside if available for internal hemorrhoids, distal source

— Bilious aspirate without blood reduces likelihood of active UGIB but does not exclude it

— Bloody/coffee-ground → upper source; proceed to EGD first

— Increasingly replaced by early EGD when suspicion for UGIB is high

— >1.0 → significant hemorrhage; >1.4 → massive transfusion likely needed

CCS pearl: in a CCS case of hematochezia, your first three orders should be (1) two large-bore IVs, (2) type & crossmatch + CBC/coags/CMP/lactate, and (3) IV crystalloid bolus — before you order colonoscopy or imaging. Reassess vitals after each intervention; the clock advances when you "reassess patient."

Vitals first — define stability before anything else:

Targeted exam:

Anorectal exam is mandatory (Step 3 will dock you if you skip it):

NG lavage (selectively useful):

Shock index (HR/SBP):

Diagnostic Workup — Initial Labs and Imaging

— CBC: hemoglobin may be falsely normal early (acute bleed before hemodilution); recheck in 4–6 hours

— Type and crossmatch ≥2 units PRBCs

— Coagulation panel (PT/INR, aPTT), platelet count

— BMP: BUN/Cr ratio >30 suggests UGIB; AKI from hypoperfusion

— LFTs (cirrhosis screen), lactate (bowel ischemia, shock)

— Troponin and ECG in elderly or with chest pain — demand ischemia from anemia is common and exam-tested

— Stool studies if diarrhea: C. difficile PCR, Shiga toxin, culture, ova & parasites if exposure

— Transfuse PRBC at Hb <7 g/dL in stable patients

— <8 g/dL if CAD, symptomatic, or ongoing bleeding

— Platelets if <50 with active bleeding; FFP if INR >1.5–2 from warfarin or coagulopathy

— Warfarin + life-threatening bleed → 4-factor PCC + IV vitamin K 10 mg

— Dabigatran → idarucizumab

— Factor Xa inhibitors (apixaban, rivaroxaban) → andexanet alfa, or 4-factor PCC if unavailable

— Hold antiplatelets; platelet transfusion generally NOT helpful for antiplatelet-associated bleeds unless thrombocytopenic or neurosurgical bleed

— CT angiography (CTA) is the first-line localization study for active LGIB with hemodynamic instability — detects bleeding ≥0.3 mL/min, no prep needed, fast

— Plain CT (without contrast) is low-yield; do not substitute

— If CTA positive → IR mesenteric angiography with embolization

Board pearl: BUN/Cr ratio >30 in a hematochezia patient should make you order an EGD first to rule out a brisk upper source, even though "lower" symptoms are present. About 10–15% of "LGIB" presentations are actually UGIB.

Core labs at presentation:

Hemoglobin thresholds for transfusion (restrictive strategy — AABB/ACG):

Reversal of anticoagulants (high-yield):

Imaging in unstable or ongoing bleed:

Diagnostic Workup — Advanced and Confirmatory Studies

— Timing: within 24 hours of presentation/resuscitation for hospitalized LGIB (ACG 2023)

— Requires adequate bowel prep: 4–6 L PEG over 3–4 hours (split-dose if outpatient)

— Diagnostic yield 70–90%; therapeutic options include clips, thermal coagulation, epinephrine injection (adjunct only), band ligation

— Identifies stigmata of recent bleed: active bleeding, visible vessel, adherent clot

— Used when colonoscopy and EGD are negative and small bowel source suspected

— Single- or double-balloon enteroscopy reaches deep small bowel

— First-line for obscure GI bleeding after negative EGD and colonoscopy

— Non-therapeutic; localizes lesions (angioectasia, Meckel's, small bowel tumors) to guide enteroscopy

— Contraindicated if known stricture (risk of capsule retention) — consider patency capsule first

— First imaging step in active brisk bleeding or hemodynamic instability before/instead of colonoscopy

— Sensitivity ~85% when bleeding ≥0.3 mL/min

— Detects slower bleeding (0.1 mL/min) but poor anatomic localization; largely replaced by CTA

— Both diagnostic and therapeutic (embolization with microcoils/gelfoam)

— Used when CTA confirms active extravasation; superselective embolization reduces ischemia risk

— Young patient with painless hematochezia → suspect Meckel diverticulum (rule of 2s)

Key distinction: CTA localizes, IR angiography treats, colonoscopy does both. Pick CTA first if patient is unstable; pick colonoscopy first if patient is stable and prepped.

Colonoscopy — the cornerstone diagnostic and therapeutic tool:

Push enteroscopy / device-assisted enteroscopy:

Capsule endoscopy:

CT angiography (CTA):

Tagged RBC (Tc-99m) scintigraphy:

Mesenteric angiography (catheter-based):

Meckel's scan (Tc-99m pertechnetate):

Risk Stratification and First-Line Management Logic

— Variables: age, sex, prior LGIB admission, DRE findings, HR, SBP, hemoglobin

— Score ≤8 → safe for outpatient management (98% chance of no adverse outcome)

— Score >8 → admit

— Hemodynamically unstable → ICU, aggressive resuscitation, reverse anticoagulation, urgent CTA → IR embolization or surgery; EGD first if UGIB suspected

— Stable, ongoing bleeding → admit, bowel prep, colonoscopy within 24 hours

— Stable, bleeding stopped, low Oakland → consider discharge with outpatient colonoscopy in 1–2 weeks

— Two large-bore (16–18 g) peripheral IVs

— Balanced crystalloid (LR or plasmalyte) bolus 500–1000 mL; reassess

— Transfuse PRBC if Hb <7 (or <8 with CAD); use 1:1:1 ratio for massive transfusion

— Permissive resuscitation — avoid over-transfusion (worsens portal pressures if variceal, dilutes clotting factors)

— Hold all anticoagulants and antiplatelets during active bleeding

— Reverse warfarin/DOACs as above for life-threatening bleeds

— Resume anticoagulation typically within 7 days after hemostasis achieved (earlier in high thrombotic risk e.g., mechanical valve); aspirin for secondary CV prevention typically resumed within 1–7 days

Step 3 management: the most common wrong answer is "urgent colonoscopy without prep." Even in active LGIB, rapid PEG prep over 3–4 hours markedly improves yield. The exception is the unstable patient — they go to CTA/IR, not the endoscopy suite.

Oakland score (validated LGIB risk score — Step 3 favorite concept):

Shock index, AIMS65, and clinical gestalt also useful, but Oakland is the LGIB-specific tool.

Triage decision tree:

Resuscitation principles:

Anticoagulant management:

NPO until source identified and intervention planned.

Pharmacotherapy — First-Line Drug Regimen

— Empiric IV PPI (pantoprazole 80 mg bolus then 8 mg/hr or 40 mg BID) is reasonable while UGIB is being excluded

— Discontinue once LGIB confirmed

— 50 mcg IV bolus then 50 mcg/hr drip — only if variceal UGIB is in differential or refractory angioectasia bleeding

— Reduces splanchnic blood flow

— Ceftriaxone 1 g IV daily x 7 days if cirrhosis with GI bleed (SBP prophylaxis — even if LGIB)

— For infectious colitis with bloody diarrhea: avoid empiric antibiotics in suspected STEC (Shiga toxin E. coli) — increases HUS risk

— C. difficile: oral vancomycin 125 mg QID or fidaxomicin

— Warfarin: 4-factor PCC (25–50 units/kg) + IV vitamin K 10 mg

— Dabigatran: idarucizumab 5 g IV

— Apixaban/rivaroxaban: andexanet alfa (high-dose if last dose <8h or unknown); alternative 4-factor PCC 50 units/kg

— Heparin: protamine sulfate 1 mg per 100 units heparin (max 50 mg)

— HALT-IT trial showed no mortality benefit and increased venous thrombosis in GI bleeding — not recommended routinely

— IBD flare with bleeding: IV corticosteroids (methylprednisolone 40–60 mg/day)

— Radiation proctitis: topical sucralfate enemas, argon plasma coagulation

— Hereditary hemorrhagic telangiectasia / refractory angioectasia: consider thalidomide, bevacizumab, or octreotide LAR

Board pearl: TXA is not standard for LGIB. If a stem offers it, look for the answer choice with PCC + vitamin K, or with definitive endoscopic/IR hemostasis instead.

There is no drug that "treats" LGIB the way PPIs treat UGIB — pharmacotherapy in LGIB centers on (1) reversing the offender, (2) supporting hemostasis, (3) treating the underlying disease.

Acid suppression:

Octreotide:

Antibiotics:

Anticoagulation reversal (high-yield):

Tranexamic acid (TXA):

Disease-specific:

Procedures — Endoscopic, Radiologic, and Surgical Hemostasis

— Diverticular bleeding: through-the-scope clips, band ligation, or thermal coagulation; epinephrine injection as adjunct only (rebleed if used alone)

— Angioectasia: argon plasma coagulation (APC) is preferred — diffuse, superficial vessels

— Post-polypectomy bleed: clips ± epinephrine, thermal

— Radiation proctitis: APC

— Hemorrhoidal bleeding: rubber band ligation (internal grade I–III), sclerotherapy

— Indicated when CTA shows active extravasation and endoscopy unavailable, failed, or unsafe

— Superselective microcoil embolization of vasa recta; success ~80–90%

— Risk: bowel ischemia (~1–4%) — superselective technique minimizes this

— Indications: hemodynamic instability despite resuscitation + transfusion (>6 units PRBC/24h), failed endoscopic and IR therapy, recurrent severe bleeding from identified segment

— Preferred: segmental resection of localized source

— Subtotal colectomy only if source cannot be localized despite repeated workup — high morbidity, avoided when possible

— Hemicolectomy without preoperative localization carries 30–50% rebleed risk from missed source

— TIPS — for variceal UGIB masquerading as LGIB; not for true LGIB

— Hemorrhoidectomy: failed banding, grade IV, thrombosed external

— Stoma for severe radiation proctitis or unresectable rectal cancer with bleeding

CCS pearl: the sequence in a bleeding patient is resuscitate → localize → treat least invasively first. Jumping to surgery before adequate endoscopic/IR attempts is a common CCS trap. Document re-bleeding episodes and transfusion requirements to justify escalation.

Colonoscopy with therapeutic intervention (first-line in stable patients):

IR mesenteric angiography with embolization:

Surgical management (last resort):

Special procedures:

Special Populations — Elderly and Renal/Hepatic Impairment

— Disproportionately affected — diverticulosis, angioectasia, ischemic colitis, neoplasia all peak in this group

— Polypharmacy (NSAIDs, antiplatelets, anticoagulants) drives bleeding risk

— Cardiac comorbidity raises transfusion threshold to Hb <8 g/dL

— Bowel prep tolerance lower — split-dose, monitor electrolytes (hyponatremia, AKI from PEG)

— Higher mortality: 1-year mortality ~20% after major LGIB; address goals of care early

— Consider frailty before subjecting to surgery

— Uremic platelet dysfunction → bleeding risk; treat with desmopressin (DDAVP) 0.3 mcg/kg IV as bridge to procedure

— Cryoprecipitate or conjugated estrogens as alternatives in severe cases

— Avoid contrast-heavy CTA if possible in advanced CKD; if needed, use isoosmolar contrast and hydrate

— Angioectasia incidence increases — recurrent bleeding source

— Dialysis patients: avoid heparin during dialysis during active bleed (citrate or heparin-free dialysis)

— Bowel prep with PEG (isoosmotic) preferred; avoid sodium phosphate preps (acute phosphate nephropathy)

— Coagulopathy is balanced, not purely hypocoagulable — INR does not reliably predict bleeding risk

— Avoid empiric FFP based on INR alone; use thromboelastography (TEG/ROTEM) if available

— Platelet goal >50 for endoscopy; consider TPO agonist (avatrombopag, lusutrombopag) for elective procedures

— Always rule out variceal UGIB first

— Ceftriaxone 1 g IV daily x 7 days for any cirrhotic with GI bleeding regardless of ascites — reduces infection and mortality

— Mechanical valve: resume warfarin within 7 days; bridge with heparin only if very high thrombotic risk

— A-fib with CHA₂DS₂-VASc ≤2: longer holds acceptable

Step 3 management: in a dialysis patient with recurrent obscure GI bleeding and negative EGD/colonoscopy → capsule endoscopy looking for small bowel angioectasia; treat with APC if found.

Elderly (≥65):

Chronic kidney disease:

Cirrhosis/hepatic impairment:

Anticoagulated patients:

Special Populations — Pregnancy, Pediatrics, and Other Subgroups

— Hemorrhoids and anal fissures are the dominant causes — increased pelvic pressure, constipation

— Treat conservatively: fiber, hydration, sitz baths, topical hydrocortisone (short course), bulk laxatives (psyllium); avoid prolonged steroid creams

— Colonoscopy generally safe in 2nd trimester if indicated; left lateral position, minimal sedation (midazolam category D — use sparingly; propofol generally preferred)

— Avoid radiation-based imaging; CTA only if life-threatening, with abdominal shielding

— IBD flare: maintain biologics; avoid methotrexate (teratogen); steroids OK short-term

— Neonate: necrotizing enterocolitis, malrotation with volvulus, milk protein allergy, swallowed maternal blood (Apt test)

— Infant/toddler: intussusception ("currant jelly" stool — late finding), Meckel diverticulum, anal fissure, milk protein colitis

— School-age: juvenile polyps (painless intermittent BRBPR), IBD, infectious colitis, HSP (palpable purpura + abdominal pain + hematuria)

— Adolescent: IBD, infectious colitis, polyps

— Meckel diverticulum: rule of 2s — 2% population, 2 feet from ileocecal valve, 2 inches long, 2 types of ectopic tissue (gastric/pancreatic), presents by age 2; diagnose with Tc-99m pertechnetate scan

— Intussusception: 6 mo–3 yr, episodic crying with leg drawing, sausage-shaped mass; air or contrast enema is both diagnostic and therapeutic

— Peutz-Jeghers: mucocutaneous pigmentation + hamartomatous polyps → intussusception, bleeding; surveillance from teens

— FAP: hundreds of polyps, near-100% CRC risk by age 40 → prophylactic colectomy

— Lynch syndrome: CRC by 40s, endometrial Ca; surveillance colonoscopy every 1–2 years starting age 20–25

— HHT (Osler-Weber-Rendu): epistaxis + telangiectasias + family history; iron-deficiency anemia from GI angioectasias

Board pearl: painless hematochezia in a child age 2–5 with no constipation = think Meckel diverticulum and order a Meckel scan, not colonoscopy first.

Pregnancy:

Pediatrics — age-stratified differential (high-yield):

Hereditary syndromes:

Complications and Adverse Outcomes

— Acute kidney injury from hypoperfusion (ATN) — monitor UOP, lactate

— Myocardial demand ischemia (Type 2 MI) — elderly with CAD and Hb <8; transfuse, treat ischemia

— Hepatic ischemia, mesenteric ischemia (especially if vasopressors needed)

— Cerebral hypoperfusion → delirium, falls in elderly

— TRALI (transfusion-related acute lung injury) — within 6 hours, bilateral infiltrates, hypoxia

— TACO (circulatory overload) — pre-existing CHF, elderly; treat with diuresis, slow transfusion

— Hemolytic reactions, febrile non-hemolytic reactions

— Citrate toxicity → hypocalcemia in massive transfusion → ECG changes, prolonged QT

— Coagulopathy and hypothermia in massive transfusion → reinforce 1:1:1 ratio

— Colonoscopy: perforation (~0.1% diagnostic, higher therapeutic), post-polypectomy bleed (up to 14 days), bowel prep–induced AKI/hyponatremia

— Angiographic embolization: bowel ischemia (~1–4%), contrast nephropathy, access site hematoma, pseudoaneurysm

— Surgery: anastomotic leak, ileus, wound infection, recurrent bleeding from missed source after blind colectomy (30–50%)

— Diverticular bleed recurrence: ~15% at 1 year, ~25% at 4 years

— Angioectasia recurrence: high (~40%) even after APC — plan repeat endoscopy as needed

— Held anticoagulation + immobility + acute illness → DVT/PE risk

— Use mechanical prophylaxis (SCDs) during active bleed; resume chemical VTE prophylaxis once hemostasis stable (typically 48–72 hours)

— Chronic blood loss → fatigue, demand ischemia, transfusion dependence

— Treat with oral iron (every other day dosing improves absorption) or IV iron (ferric carboxymaltose, sucrose) if intolerant or malabsorption

Key distinction: TRALI (hypoxia + bilateral infiltrates, no volume overload) vs TACO (hypoxia + volume overload, JVD, BNP elevated) — both during/after transfusion; management diverges (supportive vs diuresis).

Hemorrhagic shock and end-organ injury:

Transfusion-related complications:

Procedural complications:

Rebleeding:

Venous thromboembolism:

Iron deficiency anemia:

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Persistent hemodynamic instability after 2 L crystalloid

— Ongoing transfusion need (>4 units PRBC in 24h)

— Active bleeding with comorbidities (CAD, CKD, cirrhosis)

— Need for vasopressors

— Post-massive-transfusion physiology (coagulopathy, hypothermia, acidosis — "lethal triad")

— Mental status changes from hypoperfusion

— GI: bedside evaluation, plan urgent colonoscopy within 24h

— Interventional radiology: CTA-positive active bleed → embolization

— Colorectal/general surgery: failed endoscopic + IR therapy, peritoneal signs, suspected aortoenteric fistula

— Hematology: complex coagulopathy, mechanical valve management, refractory bleeding

— Anesthesia: airway protection in upper GI source with hematemesis or altered mental status

— Telemetry: stable but ongoing bleed, anticoagulated, CAD, age >70

— Floor: stable, isolated event, low Oakland score awaiting outpatient colonoscopy

— ICU: as above

— Massive bleeding (>6 units PRBC/24h)

— Failed two endoscopic attempts and failed IR embolization

— Pulsatile abdominal mass + GI bleed + prior aortic graft → aortoenteric fistula — emergent vascular surgery, do NOT delay for elaborate workup

— If facility lacks IR or therapeutic endoscopy → arrange early transfer once initial resuscitation under way; do not wait for stability that may never come

— Communicate transfusion totals, anticoagulant reversal status, NPO time clearly

CCS pearl: on CCS, "consult GI" is not a free pass — you must still order resuscitation, type & cross, NPO, and serial vitals/CBC yourself. The clock advances faster when you have appropriate orders running in parallel; sequential ordering wastes simulated time.

ICU admission criteria:

Consultations to mobilize early:

Floor vs telemetry vs ICU triage:

Indicators for surgical urgency:

Transfer-of-care considerations:

Key Differentials — Same-Category (Lower GI) Causes

— #1 cause of major LGIB; painless, abrupt, large-volume

— Right-sided diverticula bleed more often than left despite being less common

— 80% stop spontaneously; rebleed risk 15–25%

— Older adults, often right colon; associated with CKD, aortic stenosis (Heyde syndrome — acquired vWF deficiency), LVAD

— Recurrent slow bleeding, iron-deficiency anemia

— APC at colonoscopy; aortic valve replacement can resolve Heyde

— Crampy LLQ pain → bloody diarrhea within hours

— "Watershed" areas: splenic flexure, rectosigmoid

— Risk: hypotension, AAA repair, vasopressors, cocaine, OCPs, hypercoagulable states, marathon running

— CT: bowel wall thickening, "thumbprinting"; colonoscopy: segmental erythema, ulcers sparing rectum

— Most cases self-limited with bowel rest, IV fluids, antibiotics if severe; surgery for transmural ischemia/peritonitis

— Bright red blood on tissue, painless (internal); painful if thrombosed external

— Diagnose by anoscopy; treat with fiber, sitz baths, banding, hemorrhoidectomy

— Pain with defecation, small amount of bright blood; posterior midline most common

— Treat: sitz baths, fiber, topical nifedipine or nitroglycerin; lateral internal sphincterotomy for chronic

— Chronic occult or intermittent overt bleeding, iron-deficiency anemia, change in bowel habits

— Any iron-deficiency anemia in man or postmenopausal woman → colonoscopy

— Bloody diarrhea + urgency + tenesmus; extraintestinal manifestations

Board pearl: new iron-deficiency anemia in any adult ≥45 = colonoscopy until proven otherwise. Don't anchor on hemorrhoids visible on exam.

Diverticular bleeding:

Angioectasia (angiodysplasia/AVM):

Ischemic colitis:

Hemorrhoids:

Anal fissure:

Colorectal cancer/polyps:

IBD (UC > Crohn for bloody diarrhea):

Infectious colitis: Shigella, Salmonella, Campylobacter, EHEC, C. difficile, CMV (immunocompromised)

Radiation proctitis: months–years after pelvic XRT for prostate/cervical cancer

Post-polypectomy bleed: up to 14 days post-procedure

Solitary rectal ulcer syndrome: young adult, straining, rectal bleeding/mucus

Key Differentials — Other-Category Causes

— Brisk UGIB (peptic ulcer with visible vessel, variceal bleed, Dieulafoy lesion, aortoenteric fistula) → hematochezia in ~10–15%

— Clues: BUN/Cr >30, hemodynamic instability disproportionate to "lower" appearance, history of cirrhosis/NSAID/aortic graft

— Workup: EGD first if any suspicion; consider empiric PPI + octreotide while pending

— Angioectasia (most common small bowel cause in elderly)

— Meckel diverticulum (young patient)

— Small bowel tumors (GIST, lymphoma, adenocarcinoma, carcinoid)

— Crohn disease

— NSAID enteropathy

— Workup: capsule endoscopy, then device-assisted enteroscopy

— Prior aortic graft + GI bleeding = AEF until proven otherwise

— Classic "herald bleed" precedes catastrophic exsanguination

— Diagnosis: CTA; treatment: emergent vascular surgery

— Supratherapeutic anticoagulation

— Liver failure, DIC, hematologic malignancy, ITP, TTP, HUS

— Always check coags and platelets early

— Vaginal bleeding, hematuria, perianal skin lesions — sort out with focused exam

— Beeturia, food coloring, iron supplements, bismuth (black stool but guaiac-negative)

— Henoch-Schönlein purpura (IgA vasculitis) — children, palpable purpura + arthralgias + abdominal pain + hematuria

— Polyarteritis nodosa — mesenteric microaneurysms, abdominal pain, GI bleed, hypertension, hepatitis B association

Key distinction: the highest-yield "don't miss" diagnoses on Step 3 stems are aortoenteric fistula (prior aortic graft) and brisk UGIB masquerading as LGIB (BUN/Cr >30, instability). Both change management entirely.

Upper GI bleeding masquerading as LGIB:

Small bowel sources (mid-GI bleed):

Hemobilia: triad of RUQ pain, jaundice, GI bleeding — after liver biopsy, trauma, hepatic artery aneurysm

Hemosuccus pancreaticus: bleeding from pancreatic duct — pseudoaneurysm complication of chronic pancreatitis

Aortoenteric fistula:

Coagulopathy mimicking primary GI bleed:

Non-GI sources confused with hematochezia:

Vasculitides:

Secondary Prevention and Discharge Planning

— Aspirin for secondary CV prevention: resume within 1–7 days after hemostasis; stopping permanently triples cardiovascular mortality

— Aspirin for primary prevention: usually discontinue — risk outweighs benefit, especially in elderly

— Dual antiplatelet therapy post-PCI: consult cardiology; balance stent thrombosis risk

— Anticoagulation (warfarin/DOAC): resume within 7 days for most; earlier in mechanical valve, recent VTE; later if recurrent or high rebleed risk

— Document the conversation and rationale clearly

— NSAIDs — switch to acetaminophen, topical NSAIDs, or other modalities

— Concomitant aspirin + DOAC unless indication clear

— SSRIs only if alternative available and bleed was significant

— Diverticular bleeding: high-fiber diet (25–35 g/day); no proven benefit from avoiding nuts/seeds/popcorn (myth)

— Angioectasia: iron supplementation, treat underlying CKD/aortic stenosis; consider somatostatin analogs for refractory cases

— Hemorrhoids: fiber 25 g/day, hydration, avoid straining, sitz baths

— Ischemic colitis: address triggers (stop offending vasoconstrictors, OCPs; treat AF)

— IBD: optimize maintenance therapy (5-ASA, biologics, immunomodulators)

— Colorectal cancer: post-surgical surveillance — CEA every 3–6 months for 2 years, CT chest/abd/pelvis annually for 3–5 years, colonoscopy at 1 year, then 3 years, then 5 years

— Oral ferrous sulfate 325 mg every other day (better absorption than daily)

— IV iron (ferric carboxymaltose) if intolerant, malabsorptive, or rapid replenishment needed

— Influenza annually, pneumococcal as indicated, COVID-19 boosters

— Colon cancer screening on schedule if not yet done

Step 3 management: the single highest-yield discharge decision is when to restart aspirin/anticoagulation — early restart (1–7 days) is correct for most patients with clear indications (CAD, mechanical valve, recent VTE, A-fib with high CHA₂DS₂-VASc).

Resumption of antithrombotics — individualized risk/benefit:

Discontinue/avoid:

Disease-specific secondary prevention:

Iron replacement:

Vaccinations and preventive care:

Follow-Up, Monitoring, and Counseling

— Primary care visit within 1–2 weeks of discharge for vitals, hemoglobin recheck, medication reconciliation

— Repeat CBC at 2 and 4 weeks to confirm hemoglobin recovery and adequate iron repletion

— GI follow-up at 4–6 weeks; outpatient colonoscopy within 2 weeks if not completed inpatient

— Address any pending biopsy results (e.g., suspicious polyps, IBD diagnosis confirmation)

— 1–2 small (<10 mm) tubular adenomas: 7–10 years

— 3–4 tubular adenomas <10 mm: 3–5 years

— 5–10 tubular adenomas, or any ≥10 mm, villous, high-grade dysplasia: 3 years

— Sessile serrated polyp ≥10 mm or with dysplasia: 3 years

— >10 adenomas: 1 year, consider genetic evaluation

— Begin at age 45 in average-risk adults; continue to 75 (individualized 76–85)

— Options: colonoscopy every 10 years, FIT annually, FIT-DNA every 3 years, CT colonography every 5 years

— Return precautions: recurrent hematochezia, melena, lightheadedness, syncope, chest pain

— Stool diary for IBD or ischemic colitis recovery

— Fiber 25–35 g/day; adequate hydration

— Avoid NSAIDs; use acetaminophen for analgesia

— Smoking cessation (worsens IBD, vascular disease)

— Alcohol moderation

— Regular physical activity

— Hb, ferritin, transferrin saturation at 4–8 weeks of iron therapy

— Continue iron 3–6 months after Hb normalizes to replete stores

— Post-hospitalization functional decline; PT/OT referral as needed

— Screen for depression after major bleed

Board pearl: post-diverticular-bleed patients do not need lifelong dietary restriction beyond high fiber; the seeds/nuts/popcorn restriction is myth and is a common exam distractor.

Outpatient follow-up cadence:

Colonoscopy surveillance intervals (post-polypectomy — USMSTF 2020):

CRC screening (USPSTF, ACS):

Symptom monitoring at home:

Lifestyle counseling:

Anemia rechecks:

Mental health and frailty screening in elderly:

Ethical, Legal, and Patient Safety Considerations

— Discuss risks (TRALI, TACO, infection, allergic reaction, alloimmunization), benefits, alternatives

— Jehovah's Witness patients: explicit discussion required; honor refusal of whole blood and PRBC even if life-threatening; many accept albumin, EPO, IV iron, cell-saver autotransfusion, factor concentrates — clarify each component

— Document the conversation; involve ethics committee if decision-making capacity unclear or pediatric patient with refusing parents (court order may be needed for life-threatening pediatric transfusion)

— Confused, septic, or shocked patient may lack capacity for refusal of transfusion or procedures

— Two-physician emergency consent permissible for life-saving treatment in patients lacking capacity without surrogate

— Use shared decision-making tools to weigh rebleed vs thrombotic risk (e.g., A-fib patient with CHA₂DS₂-VASc 4 and HAS-BLED 4)

— Document rationale for restart timing

— Medication reconciliation at discharge — explicitly document what was held, restarted, and timing

— Closed-loop communication with PCP and GI about pending biopsy results and follow-up colonoscopy

— Send discharge summary within 48 hours; teach-back method to confirm patient understanding

— Elder abuse if exam reveals signs of neglect/abuse → APS notification

— Disclosure of medical errors (e.g., missed UGIB source, delayed colonoscopy) — be honest, apologize, document, system review

— Time-out before colonoscopy/endoscopy; verify consent, allergies, anticoagulant status

— Sedation safety in elderly — start low, monitor capnography

— CRC screening disparities by race/insurance — advocate for accessible screening options (FIT for underserved)

— In frail elderly or terminal patients with recurrent severe bleeding, discuss goals of care, palliative options, transfusion limits

Step 3 management: when a Jehovah's Witness with severe LGIB and Hb 5 refuses transfusion — confirm capacity, document refusal, escalate non-blood strategies (IV iron, EPO, cell-saver during surgery, hemostatic agents) and proceed with definitive source control. Do not transfuse against documented wishes of a competent adult.

Informed consent for blood transfusion:

Capacity assessment:

Anticoagulation decisions and shared decision-making:

Transitions of care — major patient safety domain:

Mandatory reporting and disclosure:

Procedural safety:

Health equity:

End-of-life considerations:

High-Yield Associations and Rapid-Fire Facts

Board pearl: when a stem mixes "prior AAA repair" with any GI bleeding, choose CTA emergently and vascular surgery consult — aortoenteric fistula has 100% mortality without surgery.

Heyde syndrome = aortic stenosis + colonic angioectasia + acquired von Willebrand factor deficiency (shear stress cleaves vWF multimers). AVR can resolve bleeding.

Diverticulosis is left-sided (sigmoid) by anatomy, but right-sided diverticula are more likely to bleed.

Painless large-volume hematochezia in elderly = diverticular bleed.

Painful crampy LLQ → bloody diarrhea in elderly = ischemic colitis.

Bloody diarrhea + recent antibiotics = C. difficile.

Bloody diarrhea + hamburger + child + HUS = EHEC O157:H7 — avoid antibiotics, avoid antimotility agents.

Currant-jelly stool + sausage mass + child <2 yr = intussusception → air enema.

Painless rectal bleeding in toddler = Meckel diverticulum → Tc-99m pertechnetate scan.

Mucocutaneous pigmentation + GI polyps = Peutz-Jeghers (STK11 mutation).

Telangiectasias + epistaxis + family history = HHT (Osler-Weber-Rendu).

Pulsatile abdominal mass + GI bleed + prior aortic graft = aortoenteric fistula → emergent vascular surgery.

BUN/Cr ratio >30 in hematochezia → suspect UGIB; do EGD first.

Restrictive transfusion threshold: Hb <7 (no CAD), <8 (CAD/symptomatic).

CTA detects bleeding ≥0.3 mL/min; tagged RBC scan ≥0.1 mL/min but poor localization.

TXA in GI bleeding = no benefit, more VTE (HALT-IT).

Cirrhosis + GI bleed = ceftriaxone 1 g IV daily x 7 days, regardless of ascites.

DOAC reversal: idarucizumab (dabigatran), andexanet alfa or 4F-PCC (apixaban/rivaroxaban).

Warfarin reversal: 4F-PCC + IV vitamin K (faster than FFP).

Oakland score ≤8 = safe outpatient management.

Subtotal colectomy without localization rebleeds 30–50% — avoid.

CRC screening starts at 45 (USPSTF, 2021 update).

Restart aspirin within 1–7 days post-bleed for secondary CV prevention.

HHT: GI angioectasias, treat with iron, APC, bevacizumab in severe cases.

Radiation proctitis: APC or topical sucralfate enemas.

Board Question Stem Patterns

— "72-year-old man on aspirin presents with painless large-volume bright red blood per rectum, BP 110/70, HR 95..."

— Next step: resuscitate, type & cross, NPO, plan colonoscopy within 24h after PEG prep

— Trap: choosing surgery, CT abdomen without contrast, or urgent unprepped colonoscopy

— "65-year-old man with cirrhosis, hematochezia, BP 85/50, HR 120, BUN 60, Cr 1.2..."

— Next step: IV PPI + octreotide + ceftriaxone, urgent EGD (not colonoscopy)

— Key clue: BUN/Cr >30 + instability

— "70-year-old man, prior AAA repair 4 years ago, presents with self-limited hematochezia followed by massive bleed..."

— Next step: CTA + emergent vascular surgery

— Trap: ordering colonoscopy first

— "78-year-old with A-fib, recent hypotensive episode, develops crampy LLQ pain then bloody diarrhea..."

— Diagnosis: ischemic colitis (splenic flexure watershed)

— Treatment: IV fluids, bowel rest, antibiotics if severe; surgery only for transmural ischemia

— "82-year-old woman with aortic stenosis murmur and recurrent bright red bleeding, iron deficiency anemia, colonoscopy shows cecal angioectasias..."

— Treatment: APC + consider aortic valve replacement

— "3-year-old with painless episode of dark red blood per rectum, hemodynamically stable..."

— Next step: Tc-99m pertechnetate scan

— "5-year-old with bloody diarrhea after eating undercooked hamburger, developing pallor and decreased urine output..."

— Diagnosis: HUS from EHEC O157:H7; avoid antibiotics

— "Patient on apixaban with massive LGIB and Hb 6..."

— Next step: andexanet alfa or 4F-PCC; transfuse PRBC; urgent localization

— "55-year-old with small-volume hematochezia, normal vitals, Hb 13, Oakland score 6..."

— Next step: discharge with outpatient colonoscopy in 1–2 weeks

CCS pearl: for CCS hematochezia cases, the highest-scoring orders are: 2 large-bore IVs, IV fluids, type & cross, CBC/coags/BMP/lactate, NPO, monitor on telemetry, GI consult, and serial vitals — all in the first 5 simulated minutes.

Pattern 1 — Classic diverticular bleed:

Pattern 2 — UGIB masquerading:

Pattern 3 — Aortoenteric fistula:

Pattern 4 — Ischemic colitis:

Pattern 5 — Heyde syndrome:

Pattern 6 — Meckel diverticulum:

Pattern 7 — EHEC vs Shigella distinction:

Pattern 8 — Anticoagulant reversal:

Pattern 9 — Outpatient triage:

One-Line Recap

Lower GI bleeding is managed by simultaneous resuscitation, localization (CTA if unstable, colonoscopy within 24 hours if stable after prep), and least-invasive hemostasis (endoscopy → IR embolization → surgery), while reversing anticoagulation, transfusing restrictively, and excluding a brisk upper GI source.

Board pearl: the highest-yield single decision on Step 3 LGIB stems is whether to scope, image, or operate first — anchor on hemodynamic stability and BUN/Cr ratio to make that call correctly every time.

Top 3 etiologies: diverticulosis, angioectasia, ischemic colitis — but always rule out brisk UGIB (BUN/Cr >30) and aortoenteric fistula (prior aortic graft).

Resuscitate first, then localize, then treat: two large-bore IVs, type & cross, hold/reverse anticoagulants, transfuse for Hb <7 (or <8 with CAD), then choose CTA (unstable) or colonoscopy after PEG prep (stable).

Discharge wisdom: restart aspirin within 1–7 days for secondary CV prevention; restart anticoagulation within 7 days in most cases; replete iron; arrange colonoscopy at 1–2 weeks if not completed; counsel high-fiber diet (no seed/nut restriction); ensure closed-loop biopsy and follow-up communication.

Don't-miss patterns: prior AAA repair + GI bleed = aortoenteric fistula (CTA, vascular surgery); cirrhosis + bleed = ceftriaxone prophylaxis; aortic stenosis + recurrent bleed = Heyde syndrome; toddler + painless hematochezia = Meckel scan; EHEC bloody diarrhea = no antibiotics.