Blood in Stool (Hematochezia): Causes, Evaluation, and When to Act

Hematochezia (bright red or maroon blood per rectum) indicates lower GI bleeding distal to the ligament of Treitz. It always warrants evaluation.

Common Causes by Anatomic Site

Anorectal (Most Common)

• Hemorrhoids: Painless bright red blood on toilet paper/dripping; associated with straining.
• Anal fissure: Sharp pain during/after BM + bright red blood on stool surface.
• Perianal abscess/fistula: Pain, swelling, purulent drainage.

Colonic

• Diverticular bleeding: Painless, often large volume, abrupt onset; elderly.
• Ischemic colitis: Sudden abdominal pain + bleeding; watershed areas (splenic flexure, rectosigmoid).
• Infectious colitis: C. difficile, Salmonella, Shigella, Campylobacter, E. coli O157:H7 — diarrhea, fever, blood.
• Inflammatory bowel disease (IBD): Ulcerative colitis (bloody diarrhea, urgency), Crohn's colitis.
• Angiodysplasia: Degenerative vascular ectasia; elderly; recurrent occult or overt bleeding.
• Colorectal cancer/polyps: Often occult; visible blood if distal/large. Screen at 45.
• Radiation proctitis: Months-years post-pelvic RT.

Upper GI (Can Present as Hematochezia if Massive/Transit Fast)

• Peptic ulcer disease, Mallory-Weiss tear, variceal bleed, Dieulafoy lesion.
• Typically melena (black, tarry), but brisk bleed → maroon/red stool.

Red Flags Requiring Urgent Evaluation

• Large volume, hemodynamic instability (syncope, tachycardia, hypotension).
• Age >50 (or >45 with risk factors) without recent colonoscopy.
• Family history of CRC/IBD.
• Weight loss, iron deficiency anemia, change in bowel habits.
• Anticoagulant/antiplatelet use.

Diagnostic Workup

1. History & physical: Digital rectal exam, anoscopy.
2. Labs: CBC, INR, iron studies, stool occult blood (if equivocal).
3. Colonoscopy (gold standard): Diagnostic + therapeutic (clip, band, inject, cauterize).
4. CT angiography / tagged RBC scan: For active bleeding if unstable for scope.
5. Capsule endoscopy / enteroscopy: If colonoscopy/EGD negative (small bowel source).

Management Principles

• Resuscitate first (IV access, fluids, blood products if needed).
• Targeted therapy: banding for hemorrhoids, clips for diverticular/angiodysplasia, resection for cancer/IBD.
• Iron replacement for chronic loss.

Never ignore rectal bleeding. Even "classic hemorrhoids" need confirmation to exclude concurrent neoplasia.