A 72-year-old woman with a history of aspirin use for secondary prevention of coronary artery disease presents with 3 episodes of bright red blood per rectum over the past 6 hours. She denies abdominal pain, weight loss, or change in bowel habits. On examination, vital signs are stable (BP 128/76, HR 88/min), and digital rectal examination reveals bright red blood on the gloved finger but no masses or hemorrhoids. Colonoscopy is planned. What is the most likely source of bleeding in this patient?

Explanation

## Lower GI Bleeding: Clinical Diagnosis ### Clinical Presentation Analysis **Key Point:** The combination of **bright red blood per rectum (BPRPR)**, **hemodynamic stability**, **absence of abdominal pain**, and **acute onset** in an elderly patient on antiplatelet therapy strongly suggests **diverticular bleeding**. ### Differential Diagnosis of LGIB | Diagnosis | Age | Presentation | Bleeding Character | Hemodynamics | Associated Features | | --- | --- | --- | --- | --- | --- | | **Diverticulosis** | >60 yrs | Acute BPRPR | Bright red, painless | Often stable | Aspirin/NSAIDs, no pain | | Internal hemorrhoids | Any | BPRPR on defecation | Bright red, streaky | Stable | Visible on anoscopy, straining | | Colorectal cancer | >50 yrs | Chronic bleeding | Dark/mixed, progressive | Variable | Weight loss, anemia, change in bowel habit | | Ischemic colitis | >60 yrs | Bloody diarrhea + pain | Dark/maroon | May be unstable | Abdominal pain, diarrhea, risk factors | ### Why Diverticulosis Is Most Likely 1. **Age:** 72 years — diverticulosis prevalence increases with age; 50% of patients >60 years have colonic diverticula 2. **Bleeding pattern:** Painless, bright red bleeding is classic for diverticular hemorrhage (artery erosion at the tip of the diverticulum) 3. **Hemodynamic stability:** Suggests lower bleeding rate, typical of diverticular bleeding 4. **Medication history:** Aspirin increases bleeding risk from pre-existing diverticula 5. **Absence of systemic symptoms:** No weight loss, anemia, or change in bowel habits (argues against malignancy) **High-Yield:** Diverticulosis accounts for 30–40% of LGIB in elderly patients and is the most common cause of painless BPRPR in patients >60 years [cite:Harrison 21e Ch 298]. ### Why Other Diagnoses Are Less Likely **Internal hemorrhoids:** - Would typically present with blood on toilet paper or streaking during defecation - Usually visible on anoscopy (not colonoscopy) - Less likely to cause 3 episodes of significant bleeding in 6 hours - No mention of straining or defecation-related bleeding **Colorectal cancer:** - Typically presents with chronic bleeding over weeks/months, not acute - Associated with weight loss, anemia, change in bowel habit (absent here) - Colonoscopy will exclude this diagnosis **Ischemic colitis:** - Presents with **abdominal pain** (often severe) + bloody diarrhea (absent in this case) - Requires risk factors: hypotension, cardiac disease, vasculitis - Hemodynamically stable patient makes this unlikely ### Diagnostic Approach ```mermaid flowchart TD A[LGIB: Bright red blood per rectum]:::outcome --> B{Hemodynamically stable?}:::decision B -->|Yes| C{Age > 60 years?}:::decision B -->|No| D[Resuscitate, ICU monitoring]:::urgent C -->|Yes| E{Painless bleeding?}:::decision C -->|No| F[Consider hemorrhoids, IBD]:::outcome E -->|Yes| G[Diverticulosis most likely]:::outcome E -->|No| H[Ischemic colitis, IBD]:::outcome G --> I[Colonoscopy for localization]:::action I --> J{Diverticulum with bleeding vessel?}:::decision J -->|Yes| K[Endoscopic hemostasis or angiography]:::action J -->|No| L[Observe, repeat colonoscopy if rebleeding]:::action ``` **Clinical Pearl:** Diverticular bleeding is typically **self-limited** (stops spontaneously in 80% of cases) and does not require intervention unless rebleeding occurs. Colonoscopy is performed to confirm the source and exclude other pathology [cite:Harrison 21e Ch 298].