What is the most common cause of lower gastrointestinal (GI) bleed in the United States (USA)?

Diverticulosis is the Most Common Cause of Lower GI Bleeding in the USA

Diverticulosis is definitively the most common cause of lower gastrointestinal bleeding in the United States, accounting for approximately 30-40% of all cases. 1, 2

Epidemiology and Prevalence

• Lower GI bleeding affects approximately 20.5-27 per 100,000 adults annually in the US 1
• The prevalence of diverticulosis increases significantly with age:
  • Present in approximately one-third of the population by age 50
  • Reaches 50% in patients older than 60 years 3
• Mean age of patients with lower GI bleeding ranges from 63-77 years 1
• Mortality rate for lower GI bleeding is approximately 2-4% 1

Major Causes of Lower GI Bleeding (in order of frequency)

1. Diverticulosis (30-40%) 1, 2, 4
2. Angiodysplasia (3-20%) 1
3. Colitis/inflammatory conditions (6-21%) 1
   • Includes inflammatory bowel disease, infectious colitis, radiation colitis
4. Colorectal neoplasms (6-15%) 1, 2
5. Anorectal sources (5-14%) 1
   • Includes hemorrhoids, anal fissures, rectal ulcers
6. Other causes (3-28%) 1
   • Includes postpolypectomy bleeding, anastomotic bleeding, aortocolonic fistula

Characteristics of Diverticular Bleeding

• Diverticular bleeding occurs when a vasa rectum (small artery) ruptures at the dome or neck of a diverticulum 5
• Key features:
  • Bleeding is typically painless and abrupt in onset
  • Usually not associated with diverticulitis 5
  • 90% of diverticula are in the left colon, but bleeding originates from the right colon in approximately 50% of cases 5
  • Spontaneous cessation occurs in about 75-90% of cases 1, 5

Risk Factors for Diverticular Bleeding

• Advanced age
• Hypertension
• Anticoagulant/antiplatelet medication use 3, 5
• Diabetes mellitus
• Ischemic heart disease 5

Diagnostic Approach

• Colonoscopy is the diagnostic procedure of choice for lower GI bleeding 4, 6
  • Successfully identifies the source in 74-82% of cases
  • Offers therapeutic capabilities
• Mesenteric angiography has a sensitivity of 42-86% and is typically reserved for cases where colonoscopy is not practical 4

Clinical Significance

• Approximately 50% of patients with diverticular bleeding require blood transfusion 3
• Recurrence rates are significant, with diverticular bleeding having the highest recurrence rate among lower GI bleeding causes 6
• Endoscopic control of bleeding has increased over time (from 1% to 4.4% in one study), with a corresponding decrease in the need for operative control 6

Understanding that diverticulosis is the most common cause of lower GI bleeding in the USA is crucial for appropriate diagnostic planning and management strategies, particularly in older adults presenting with hematochezia.