Definition of Hematochezia
Hematochezia is the passage of bright red blood or blood clots from the rectum. 1, 2
Key Distinguishing Features
- The term applies to both current and historical episodes of rectal bleeding characterized by bright red blood. 2
- The bright red appearance indicates blood has not been exposed to gastric acid long enough for digestion, distinguishing it from melena (black, tarry stools containing digested blood). 1
- Hematochezia is also called "bright red blood per rectum" or simply "rectal bleeding" in clinical practice. 1
Critical Clinical Context
Expected Source Location
- The bright red color typically suggests a lower gastrointestinal source (distal to the ligament of Treitz), because rapid transit prevents blood digestion. 1
Important Exception—Upper GI Bleeding Can Present as Hematochezia
- Approximately 10-15% of patients presenting with acute severe hematochezia actually have an upper gastrointestinal source identified on upper endoscopy, particularly when bleeding is massive and transit time is rapid. 1, 2
- This occurs because brisk upper GI hemorrhage can transit through the bowel quickly enough to remain bright red. 3
Clinical Pitfall to Avoid
- Never assume hematochezia automatically means lower GI bleeding—in patients with severe hematochezia and hemodynamic instability, upper endoscopy should be performed early to exclude an upper GI source. 2
- Do not attribute hematochezia to hemorrhoids without complete evaluation, as hemorrhoids alone rarely cause significant anemia and cannot be reliably diagnosed by history alone. 2, 4