bloody diarrhea
Summary
Bloody diarrhea is the passage of loose, watery stools containing visible blood, indicating inflammation or damage to the intestinal mucosa. It commonly results from infectious enterocolitis, inflammatory bowel disease, or ischemic colitis. The presence of blood distinguishes it from secretory diarrhea and suggests mucosal invasion or ulceration.
Detail
Bloody diarrhea (dysentery) results from inflammation, ulceration, or invasion of the colonic or distal ileal mucosa, leading to disruption of the intestinal barrier and bleeding. Infectious causes include invasive bacterial pathogens (Shigella, Salmonella, Campylobacter, EHEC, C. difficile), parasites (Entamoeba histolytica), and some viruses. Non-infectious causes include inflammatory bowel disease (ulcerative colitis, Crohn's disease), ischemic colitis, radiation colitis, and malignancy. The pathophysiology involves mucosal inflammation with neutrophil infiltration, epithelial cell death, and increased vascular permeability. Clinically, patients present with frequent small-volume stools mixed with blood, mucus, and pus, often accompanied by tenesmus, cramping, and fever. Diagnosis requires stool analysis including culture, ova and parasites, C. difficile toxin, and sometimes colonoscopy. Complications include dehydration, electrolyte imbalances, toxic megacolon, and in severe cases, perforation or sepsis.
Sources
- First Aid for the USMLE Step 1
- Harrison's Principles of Internal Medicine
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease
- UpToDate: Approach to the adult with acute diarrhea
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.