What are the differential diagnoses and management approaches for a patient presenting with hematochezia (blood in stool)?

Differential Diagnoses for Blood in Stool

The differential diagnosis for hematochezia is broad and age-dependent, but the most common causes in adults are diverticulosis (30-41%), angiodysplasia (20-40%), hemorrhoids (14-24%), and ischemic colitis (6-21%), while approximately 10-15% of patients presenting with severe hematochezia actually have an upper GI source. 1

Common Lower GI Sources

Colonic Causes

• Diverticular bleeding: Most common cause in older adults (30-41% of cases), typically presents as painless, large-volume bright red blood 1
• Angiodysplasia: Second most common (20-40%), particularly in patients >65 years, often associated with chronic kidney disease and aortic stenosis 1
• Inflammatory bowel disease (UC/Crohn's): In UC, bleeding occurs from diffuse mucosal ulceration in pancolitis; in Crohn's, from focal vessel erosion that can involve small bowel 1
• Ischemic colitis: Accounts for 6-21% of cases, typically in elderly with vascular disease 1
• Colorectal cancer/polyps: Represents 11-22% of cases, risk increases with age and family history 1
• Infectious/inflammatory colitis: Consider in patients with diarrhea, fever, recent antibiotic use, or travel history 2

Anorectal Causes

• Hemorrhoids: Very common (14-24% of bleeding cases), typically bright red blood coating stool or on toilet paper, may have associated prolapse or thrombosis 1
• Anal fissure: Presents with postdefecatory pain and minor bleeding, best visualized with anal eversion 1
• Anorectal varices: Distinct from hemorrhoids, cross the dentate line into rectum, associated with portal hypertension 1
• Perianal abscess/fistula: Associated with pain, fever, and palpable mass 1

Small Bowel Sources

• Small bowel bleeding: Accounts for 0.7-9% of hematochezia cases, often from angiodysplasia, tumors, or Meckel's diverticulum 1, 3

Critical Upper GI Sources (Must Exclude)

Up to 15% of patients with severe hematochezia have an upper GI bleeding source, including peptic ulcer disease, gastritis, or esophageal varices 1. This is particularly important in patients with hemodynamic instability, hemoglobin drop ≥1.5 g/dL, or transfusion requirements 1.

Age-Specific Considerations

• Patients >65 years: Diverticulosis and angiodysplasia predominate 1
• Younger patients (<50 years): Hemorrhoids, anal fissures, and IBD are more common, though colorectal cancer risk ranges from 2.4-11% and cannot be excluded based on age alone 1, 4

Less Common but Important Causes

• Radiation proctitis: Occurs 9 months to 4 years after pelvic radiation 1
• Solitary rectal ulcer syndrome: Can present with massive bleeding 1
• Post-polypectomy bleeding: Iatrogenic cause in patients with recent colonoscopy 1
• Aortoenteric fistula: Rare but catastrophic, consider in patients with prior aortic graft surgery 1

Key Diagnostic Pitfalls

Never assume hemorrhoids are the cause without proper evaluation. Hemorrhoids do not cause occult blood positivity on stool testing, and symptoms attributed to hemorrhoids frequently represent other pathology including colorectal cancer 1. A careful anorectal examination with anoscopy is mandatory, and colonoscopy is indicated when bleeding is atypical, no source is evident on anorectal exam, or risk factors for neoplasia exist 1.

Portal hypertension causes anorectal varices, not hemorrhoids. These are distinct entities requiring different management—standard hemorrhoid treatments should never be used for variceal bleeding 1. Varices are compressible, serpiginous submucosal veins that cross the dentate line, while hemorrhoids are confined to the anal canal 1.