What are the causes of gastrointestinal (GI) bleeding?

Causes of Gastrointestinal Bleeding

Gastrointestinal bleeding is primarily caused by peptic ulcer disease, diverticulosis, angiodysplasia, and inflammatory conditions, with the specific etiology varying by anatomical location and patient age. 1, 2

Anatomical Classification of GI Bleeding

GI bleeding is classified based on anatomical location:

• Upper GI bleeding: Occurs above the ampulla of Vater (accessible by EGD)
• Mid GI bleeding: Occurs from the ampulla of Vater to terminal ileum
• Lower GI bleeding: Occurs in the colon 1

Upper GI Bleeding Causes (35-50% of all GI bleeds)

• Peptic ulcer disease (35-50%)
• Gastroduodenal erosions (8-15%)
• Esophagitis (5-15%)
• Esophageal varices (5-10%)
• Mallory-Weiss syndrome (15%)
• Vascular malformations (1%) 2, 3

Less Common Upper GI Causes

• Cameron's erosions in hiatal hernias
• Fundic varices
• Dieulafoy's lesion
• Gastric antral vascular ectasia
• Neoplasms
• Hemobilia
• Hemosuccus pancreaticus
• Aortoenteric fistula 1, 2

Lower GI Bleeding Causes

• Diverticulosis (30-56%)
• Angiodysplasia/vascular ectasias (3-40%)
• Colorectal cancer/polyps (6-15%)
• Colitis/ulcers (10-21%)
  • Inflammatory bowel disease
  • Infectious colitis
  • Ischemic colitis
  • Radiation colitis
• Anorectal causes (5-14%)
  • Hemorrhoids
  • Anal fissures
  • Rectal varices 1, 4, 5

Small Intestinal Bleeding Causes

• Angiodysplasia (most common in patients >40 years)
• Crohn's disease
• NSAID-induced small bowel disease
• Dieulafoy's lesion (more common in younger patients)
• Small bowel tumors (more common in younger patients)
• Meckel's diverticulum 1, 4

Age-Related Patterns

• Younger patients (<40 years): More likely to have Dieulafoy's lesion, Crohn's disease, and small bowel tumors
• Older patients (>40 years): More prone to vascular lesions (up to 40% of all causes), diverticular disease, and NSAID-induced pathology 1

Risk Factors for GI Bleeding

• Advanced age (8-200 fold increase from age 20-80)
• Medication use:
  • Anticoagulants (warfarin, direct oral anticoagulants)
  • Antiplatelet agents (aspirin, NSAIDs)
  • High-dose NSAIDs
• H. pylori infection
• Alcohol consumption
• Smoking
• Pre-existing liver disease
• History of prior GI bleeding 2, 6, 7, 3

Clinical Presentation Clues

• Hematemesis: Suggests upper GI source
• Melena (black, tarry stools): Typically upper GI source, requires 50-100 mL of blood
• Hematochezia (bright red blood per rectum): Usually lower GI source, but can occur with brisk upper GI bleeding
• Painless bleeding: Typical of lower GI bleeding
• Associated symptoms: May provide clues to source (e.g., partial obstruction suggesting malignancy) 2, 3

Important Clinical Considerations

• 10-15% of patients presenting with acute hematochezia actually have an upper GI source
• Small bowel sources account for only 0.7-9.0% of severe hematochezia cases
• Upper GI bleeding ceases spontaneously in 75-85% of cases, but mortality remains significant (up to 14%)
• Obscure GI bleeding is defined as persistent bleeding without obvious etiology after EGD, colonoscopy, and radiologic evaluation 1, 2, 8

Understanding the anatomical location and potential causes of GI bleeding is essential for appropriate diagnostic workup and management, with age and clinical presentation providing important clues to the underlying etiology.