Published May 09, 2023 by

Blood in stool - Hematochezia, Enterorrhagia, Melena

 Blood in the stool ​

The presence of blood in the stool, whether live or digested (usually in the form of dark or black stools), always causes great apprehension to the patient and his family. 

Anal bleeding can have several causes, from simple and benign injuries, such as hemorrhoids or anal fissure, to more serious digestive bleeding, such as those caused by stomach ulcers or intestinal tumors.

Classification according to origin 

Digestive bleeding (bright or dark blood in the stool) according to its origin can be:

- Upper gastrointestinal bleeding: bleeding that occurs in the upper gastrointestinal tract, i.e. duodenum, stomach or esophagus. 

- Lower digestive bleeding: bleeding that occurs in the lower gastrointestinal tract, 

Classification according to bleeding characteristics 

Blood in the stool can be characterized as: hematochezia, enterorrhagia, melena and occult. 


It is the name given to the presence of live blood in small or moderate amounts, which is involved in the feces, drips into the toilet or toilet paper and only appears when the patient has a bowel movement. 

Hematochezia is a typical sign of lower digestive, sigmoid, rectum, and anal bleeds.


It is the name given to the presence of live blood in a large volume and usually silent, that is, without abdominal pain. In this case, the patient can evacuate only blood, without the presence of feces. It is a sign of severe gastrointestinal bleeding, which can originate anywhere in the gastrointestinal tract, the colon being most common.

3. melena 

It is the name given to black stools, usually pasty and very bad smelling, and is due to large amounts of blood retained for some time in the digestive tract. Most of the time, it is related to an upper digestive hemorrhage, in the esophagus, stomach and duodenum. But they can also originate in the right colon. This appearance of melena occurs because the blood is digested by the gastrointestinal tract before being eliminated in the stool. 


Small amounts of bleeding from the upper digestive tract and especially from the colon, are usually mixed with the stool and go unnoticed by patients, being detected only by the fecal occult blood test. In some cases, the bleeding may be small but constant, causing anemia from chronic blood loss. Iron-deficiency anemia is sometimes the only clue to hidden digestive bleeding.

Bloody stools are often signs of injury or disease present in the digestive tract. About 50 to 75% have anal and colorectal origin, 10 to 25% have origin in the esophagus, stomach and small intestine and, in 10 to 25% of cases, it is not possible to identify the exact site of bleeding. 

Small amounts of anorectal bleeding (hematochezia) 

Small amounts of blood in the stool or bleeding that is detectable only after wiping the anus with toilet paper are the most common forms of rectal bleeding. In 90% of cases, the etiology is benign. 

The main causes of small volume rectal bleeding are: 

Hemorrhoidal disease (hemorrhoids) 

Anal fissure 

Colorectal polyp 

Proctitis (rectitis) 

ulcers in the rectum 

Colorectal cancer (mainly rectum) 

anal cancer 

Intestinal endometriosis 

The two most common causes of small amounts of anorectal bleeding are hemorrhoids and anal fissures. These two account for almost 90% of cases of small-volume bleeding in the stool.


Typically manifest as bleeding when defecating, sometimes associated with pain and hemorrhoid prolapse. It is of a small amount, usually involves at the end of the stool, drops of blood that appear after a bowel movement or blood stains on toilet paper after cleaning the anus. Hemorrhoids, when large, can be easily seen by the patient himself. 

2.Anal fissures 

Usually cause pain on defecation (usually severe, tearing-like) and bleeding is usually small amounts around the stool or on paper after cleaning the anus. The distinction between anal fissure and hemorrhoids is made through visual examination of the anus and anoscopy. Despite the small volume, these small anorectal bleedings, when they occur chronically, can cause anemia.

Moderate to heavy anal bleeding (enterorrhagia)

The passage of bright red blood without stool through the anus (enterorrhagia) originates in the colon, rectum or anus in 85% to 90% of cases. 

Lower digestive bleeding (colon, rectum and anus) 

1. Diverticular disease of the colon 

Diverticulum is a protrusion from the wall of the intestine. They are small bags, similar to the fingers of gloves, that occur mainly in the wall of the colon due to weakening of its musculature. It is very common after the age of 60 and is usually multiple lesions along the large intestine. 

Diverticula are benign changes, they have nothing to do with cancer, but they can bleed or become inflamed. Diverticular disease is one of the main causes of heavy bleeding in elderly patients. 

2. Vascular Ectasia 

Vascular ectasias are collections of dilated blood vessels that appear under the inner lining of the colon. Although vascular ectasias can occur anywhere in the colon, they are most common in the ascending colon (right colon) and cecum. Vascular ectasias are more exposed and more fragile vessels, which rupture more easily. 

Bleeding from vascular ectasias is more common after the age of 60, and is usually painless and with bright blood around the stool. However, vascular ectasia can cause from massive bleeding to an asymptomatic condition, where the patient has only occult blood loss.

3. Colorectal cancer 

Approximately 10% of gastrointestinal bleeding in people over 50 years of age are secondary to bowel tumors. Tumor bleeding is usually small and may go unnoticed. 

In addition to the loss of blood in the stool, visible to the naked eye or not, patients with malignant tumors of the colon also usually show other signs, such as stringy stools (thin stools), constipation of recent onset or worsening of a chronic constipation condition. , abdominal pain, weight loss and/or anemia. 

4. Intestinal infection 

Infections with Salmonella, Campylobacter, Shigella or E.coli bacteria can cause severe intestinal infection, with fever, prostration and bloody diarrhea. Ameba and worm infections can also cause a similar condition. 

5. Inflammatory bowel disease. 

Crohn's Disease and Ulcerative Colitis. 

Crohn's disease and ulcerative colitis are inflammatory bowel diseases of unknown origin that also manifest with bleeding in the stool. The picture is usually colic and bloody diarrhea with mucus that comes on suddenly and can be continuous or periodic.


Digestive bleeding can have several different presentations, the most common are: 

★Occult blood in the stool, that is, the absence of visible bleeding, which is detected only through stool tests done by clinical analysis laboratories. 

★Iron deficiency anemia without any other signs or symptoms. 

★Bleeding detected after cleaning the anus with toilet paper. 

★Small rectal bleeding after defecation, which is characterized by drops of blood in the toilet bowl. 

★Small amounts of blood around the stool. 

★Stools with a moderate amount of blood around them. 

★Pasty, black stools with a very strong odor. 

★Rectal bleeding with fresh blood in great quantity, with oo without stool.

Differential diagnosis of the presence of blood in the stool 

It is important to be aware of the following signs that may indicate problems in the intestine: 

➤ Reddish color of toilet water after evacuating; 

➤ Presence of blood on toilet paper; 

➤ Reddish spots in the stools; 

➤ Very dark, pasty and smelly stools. 

What to do in case of blood in the stool! 

Upon noticing the presence of blood in the stool, the individual should go to the coloproctologist as soon as possible, so that the investigation can be carried out. The propaedeutic approach for lower digestive bleeding aims to answer three important questions: volume of blood lost, bleeding site and cause. 

The differential diagnosis is extensive, however, through the anamnesis, collecting the complete history of the patient, as well as relating the symptoms to the patient's age, one can help in the diagnostic definition. The physical examination, in turn, allows assessing the severity of the bleeding through the patient's cardiovascular assessment, including heart rate and blood pressure. 

Diagnostic confirmation is performed mainly through proctological and hematological examinations and colonoscopy. 

The proctological examination includes inspection and palpation of the anal canal, as well as performing a rectal examination, anoscopy and rectosigmoidoscopy. Rectal touch can identify painful points, hardening or irregularities that could be the seat of bleeding. The hematological examination, in turn, aims to quantify the blood lost by the patient through the coagulogram.​ 

Finally, colonoscopy is the main exam in the diagnosis of lower digestive bleeding, and can, in most cases, identify the site and cause of enterorrhagia.