Differential diagnosis of bloody stool

1. Big picture

Bloody stool is gastrointestinal bleeding until proven otherwise. In the exam, the safest answer is not “hemorrhoids”; it is:

Assess severity → stabilize → decide upper vs lower source → perform rectal examination/rectoscopy/colonoscopy → treat the bleeding cause.

The key trap is that bright red blood per rectum usually suggests lower gastrointestinal bleeding, but massive upper gastrointestinal bleeding can also present as hematochezia because blood passes rapidly through the bowel.

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