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usmle step 2 ck

Lower GI Bleeding

Bleeding distal to the ligament of Treitz, most often presenting with hematochezia from diverticulosis, angiodysplasia, ischemic colitis, IBD, hemorrhoids, or cancer

Review date
reviewed 2026-05-04
Reading time
8 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Gastroenterology & Hepatologycommonacute
On this page
Condition details
Gastroenterology & Hepatology
common
8 min read
reviewed 2026-05-04
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About This Page

This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.

Key points

  • Most common cause of acute severe LGIB in adults: diverticular bleeding — painless hematochezia
  • Unstable hematochezia can be brisk UGIB until proven otherwise
  • Colonoscopy after bowel preparation is the usual diagnostic and therapeutic test once stable
  • CT angiography is preferred for ongoing brisk bleeding when colonoscopy is not feasible
  • Never attribute rectal bleeding to hemorrhoids without considering age, anemia, weight loss, bowel habit change, or family history

Overview

Lower GI bleeding usually presents as hematochezia, although right-sided colonic bleeding can appear maroon. Causes vary by age: hemorrhoids/fissures in younger patients, diverticulosis and angiodysplasia in older adults, and colitis or malignancy across risk groups.

Epidemiology

LGIB is common in older adults. Diverticular hemorrhage is typically arterial, abrupt, painless, and often self-limited. Angiodysplasia is associated with older age, CKD, aortic stenosis, and von Willebrand disease. Colorectal cancer incidence is rising in younger adults.

Clinical Features

Symptoms
Bright red blood per rectum or maroon stools
Painless large-volume bleeding suggests diverticular hemorrhage
Crampy abdominal pain and bloody diarrhea suggest ischemic or inflammatory colitis
Tenesmus, urgency, mucus, and chronic diarrhea suggest ulcerative colitis
Weight loss, change in bowel habits, or iron deficiency anemia suggests malignancy
Syncope or chest pain from acute blood loss
Signs
Orthostatic hypotension or tachycardia
Abdominal tenderness with colitis, ischemia, or diverticulitis
Anorectal exam may show hemorrhoids or fissure but does not exclude proximal pathology
Peritonitis suggests ischemia, perforation, or complicated diverticulitis

Investigations

First-line
CBC, CMP, PT/INR, type and screenAssess severity, renal function, anticoagulation, and need for blood products
Digital rectal/anoscopic examConfirms blood and evaluates anorectal source, fissure, mass, or hemorrhoids
Second-line
ColonoscopyPreferred diagnostic and therapeutic test after adequate bowel preparation in most stable patients
CT angiographyLocalizes active bleeding rapidly in ongoing brisk bleeding
EGDIf hematochezia with hemodynamic instability or high suspicion of upper source
Specialist
Tagged RBC scanDetects intermittent low-rate bleeding but localizes less precisely than CTA
Catheter angiographyAllows embolization when CTA localizes active bleeding

Management

ACG Guideline for Acute Lower GI Bleeding
1
Initial approach
  • ABCs, two large-bore IVs, resuscitation
  • Hold/reverse anticoagulants for severe bleeding when appropriate
  • Restrictive RBC transfusion in most patients, individualized for ischemia
  • If unstable hematochezia, evaluate for UGIB
2
Stable patient
  • Bowel preparation followed by colonoscopy
  • Endoscopic therapy for active bleeding/high-risk stigmata
  • Treat source-specific disease: diverticular bleed, angiodysplasia, colitis, hemorrhoids, cancer
3
Severe ongoing bleeding
  • CT angiography for active bleeding localization
  • Interventional radiology embolization for localized arterial bleeding
  • Surgery is last resort, ideally after localization

Complications

  • Hemorrhagic shock: Especially with brisk diverticular bleeding.
  • Recurrent bleeding: Common after diverticular hemorrhage or angiodysplasia.
  • Missed colorectal cancer: Avoid anchoring on hemorrhoids.
  • Ischemic colitis complications: Stricture, necrosis, perforation.
USMLE Step 2 CK Exam Tips
  • 1Painless massive hematochezia in an older adult = diverticular bleeding
  • 2Painful bloody diarrhea after hypotension or vascular disease = ischemic colitis
  • 3Unstable hematochezia can be upper GI bleeding
  • 4Colonoscopy needs bowel prep; CTA is better for brisk ongoing bleeding
  • 5Aortic stenosis + recurrent painless bleeding = angiodysplasia/Heyde syndrome
  • 6Hemorrhoids do not explain iron deficiency anemia until other causes are excluded
  • 7Right-sided colon cancer can present with occult bleeding and iron deficiency anemia

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Verified Sources & References

ACG Clinical Guideline: Acute Lower GI Bleeding
ACG Clinical Guideline: Colorectal Cancer Screening 2021
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