Rectal Bleeding: Causes, Red Flags & When to See a Doctor

Rectal bleeding (hematochezia) is never normal. While often benign, it can signal serious pathology. Seek medical evaluation for any rectal bleeding, especially if accompanied by:

• Age ≥45 (or ≥40 with family history)
• Change in bowel habits (caliber, frequency, consistency)
• Unintentional weight loss
• Anemia symptoms (fatigue, pallor, dyspnea)
• Abdominal pain, fever
• Family history of colorectal cancer or IBD

Common Causes (Bright Red vs. Dark/Maroon)

Bright Red (Lower GI)	Dark/Maroon (Proximal)
Hemorrhoids (internal)	Diverticular bleeding
Anal fissure	Angiodysplasia
Proctitis (IBD, infectious, radiation)	Right-sided colon cancer
Rectal ulcer / prolapse	Small bowel bleeding (Dieulafoy, AVM)
Distal colorectal cancer / polyps	Upper GI bleed (melena if slow; hematochezia if massive)

Other Considerations

• Medications: Anticoagulants, NSAIDs, SSRIs increase bleeding severity.
• Trauma: Foreign body, anal intercourse.
• Infectious: STIs (syphilis, HSV, LGV), amebiasis.

Diagnostic Pathway

1. History & digital rectal exam (DRE).
2. Anoscopy/proctoscopy (office).
3. Colonoscopy (gold standard ≥45 or risk factors).
4. CT angiography / tagged RBC scan for active obscure bleeding.
5. Capsule endoscopy / deep enteroscopy for small bowel.

Do not self-diagnose as "just hemorrhoids." Early colorectal cancer detection saves lives.