A 65-year-old man with chronic kidney disease presents with a 2-day history of melena. Upper endoscopy shows no source of bleeding. Colonoscopy reveals a bleeding lesion in the cecum. What is the most common cause of lower gastrointestinal bleeding in this age group?

Explanation

## Most Common Cause of Lower Gastrointestinal Bleeding in Older Adults ### Epidemiology and Age-Related Patterns **Key Point:** Diverticular disease is the most common cause of acute lower GI bleeding in patients >60 years, accounting for 30–40% of cases. The incidence increases dramatically with age due to increased prevalence of colonic diverticula. ### Pathophysiology of Diverticular Bleeding 1. Diverticula form at sites of vasa recta penetration through the colonic wall 2. Bleeding occurs when a vessel erodes into the diverticulum 3. Typically painless and can be brisk 4. Right colon diverticula are more likely to bleed than left-sided ones ### Age-Related Causes of Lower GI Bleeding | Age Group | Most Common Cause | Characteristics | |-----------|-------------------|------------------| | <40 years | Hemorrhoids, anal fissures | Visible blood on stool, pain | | 40–60 years | Hemorrhoids, polyps | Mixed presentation | | >60 years | Diverticular disease | Painless, brisk bleeding | | >70 years | Angiodysplasia, diverticulosis | Chronic/recurrent bleeding | **High-Yield:** In a patient >60 with acute lower GI bleeding and a cecal lesion on colonoscopy, diverticular disease is the most likely diagnosis, even if the exact diverticulum is not visualized. ### Clinical Pearl Diverticular bleeding is typically: - **Painless** (unlike inflammatory bowel disease or ischemic colitis) - **Brisk** (can require transfusion) - **Self-limited** in ~80% of cases - More common in the **right colon** in Western populations (due to different muscle wall anatomy) ### Why Other Options Are Less Common in This Age Group **Hemorrhoids:** Most common cause of visible blood per rectum overall, but usually causes small-volume bleeding and is often recognized by patient. Not typically the cause of melena or significant bleeding in elderly. **Colorectal cancer:** Accounts for ~10% of lower GI bleeding. Typically presents with chronic bleeding and weight loss, not acute brisk bleeding. Would be visible as a mass, not just a bleeding site. **Ischemic colitis:** Occurs in elderly with vascular disease but accounts for <5% of lower GI bleeding. Presents with pain, diarrhea, and systemic toxicity—not isolated painless bleeding. **Mnemonic:** **DIVA** — Diverticulosis, Inflammatory bowel disease, Vascular (angiodysplasia), Anal/hemorrhoids. Diverticulosis is first in frequency in older adults. [cite:Harrison 21e Ch 298]