What does "hematochezia" mean and how does it differ from "melena"?

Hematochezia means the passage of bright red or maroon blood through the rectum, from hemato meaning blood and chezia meaning defecation. It typically indicates bleeding from the lower gastrointestinal tract, such as the colon or rectum, from sources like hemorrhoids, diverticulosis, or colorectal cancer. Melena means black, tarry, foul-smelling stools indicating digested blood from upper gastrointestinal bleeding, such as a stomach ulcer. The blood appears black because it has been partially digested by stomach acid and intestinal enzymes during transit.