Hematochezia is the passage of bright red, bloody stools from the rectum[1]. It is also known as "bright red blood per rectum" and abbreviated BRBPR. It is distinguished from melena, which is stool with blood that has been altered by the gut flora and appears black/"tarry". Hematochezia is commonly associated with lower gastrointestinal bleeding.

In adults, most common causes are hemorrhoids and diverticulosis, both of which are relatively benign; however, it can also be caused by colorectal cancer, which is frequently fatal. In a newborn infant, hematochezia may be the result of swallowed maternal blood at the time of delivery, but can also be an initial symptom of necrotizing enterocolitis, a serious condition affecting premature infants. In adolescents and young adults, inflammatory bowel disease, particularly ulcerative colitis, is a serious cause of hematochezia that must be considered and excluded.

Hematochezia can be due to upper gastrointestinal bleeding. However, as the blood from such a bleeding is usually chemically modified by action of acid and enzymes, it presents more commonly as melena. Hematochezia from an upper gastrointestinal source is an ominous sign, as it suggests a very brisk bleed which is life threatening.