Blood in the stool can come from many sources. The causes range from not harmful to very serious conditions. A common way to divide causes of bleeding is based on the source of bleeding. The
GI tract can be divided into upper and lower, with some causes of bleeding affecting the entire tract (upper and lower). Blood in the stool often appears different depending on its source. These differences can help when diagnosing these conditions. The rate of bleeding can also make blood in the stool look different from typical cases.
Upper GI tract The upper GI tract is defined as the organs involved in digestion above the
ligament of Treitz and comprises the
esophagus,
stomach, and
duodenum.
Pathophysiology The development of blood in a person's stool results from a variety of conditions, which can be divided into major categories of disease. These broad categories include cancerous processes or abnormal structure of bowel wall, inflammatory disease, colitis caused by infection or medications and vascular compromise. •
Gastric cancer Gut wall changes Motility The gut wall is important for the movement of waste products through the GI tract. Repetitive attempts to have a bowel movement can lead to tearing around the exit of the
rectum (anal fissure) •
Constipation Structural This list of diagnoses include diseases in which the wall of the bowel is compromised by disease.—divided into either duodenal or gastric ulcers, most common causes include: •
Nonsteroidal anti-inflammatory drugs—the use of these medications results in a structural change in the wall of the gut, namely ulcers, and potential blood in the stool. • Chronic disease and
diverticulosis result from an out pouching of the colonic mucosa, or gut wall, leading to a breakdown of weak gut wall and an increased susceptibility to infection due to the bacteria in the GI tract, thus the potential for vascular compromise, the collection of bacteria in the area of
perforation (
abscess), the abnormal formation of communication between another part of the hollow GI tract (
fistula), or blockage of the bowel (obstruction). If a portion, or all of this duct remains a
diverticulum or
fistula can result, leading to the potential for a source of bleeding. Inflammation can occur anywhere along the GI tract in
Crohn's disease, •
Crohn's disease •
Ulcerative colitis Colitis •
Enteritis—inflammation of the small intestine, which has many causes including
autoimmune conditions (e.g.
Crohn's disease), certain drugs (e.g.
ibuprofen),
radiation therapy, and
Coeliac disease.
Infectious colitis •
Food poisoning—the bacteria that is associated with bloody diarrhea is typically
E. coli •
Campylobacter enteritis •
Shigellosis •
Salmonellosis (
Salmonella enteritis/Salmonella
enterocolitis) •
Bacterial gastroenteritis •
Campylobacter jejuni •
Clostridioides difficile •
Escherichia coli enteritis—most common cause of
travelers' diarrhea •
Salmonella enterica •
Shigella dysenteriae Vascular compromise •
Angiodysplasia of the GI tract •
Arteriovenous malformation •
Anal fissure •
Anal intercourse •
Esophageal varices •
Hemorrhoids • Internal hemorrhoids are covered by a layer of
mucosa and
epithelium, making them more likely to bleed, but typically do not cause pain. • External hemorrhoids are less likely to bleed, they are covered by a different type of epithelium (
squamous) but can cause significant pain as a result of
thrombosis of the blood vessels within them. •
Polypectomy during a colonoscopy can lead to a small amount of bleeding seen in the stool after the procedure
Other causes • Blood in the diet, for example, the traditional diet of the
Maasai includes much blood drawn from cattle. == Diagnosis ==