Blood in Stool (Rectal Bleeding)

Blood in stool or rectal bleeding is also known as "hematochezia." Frank or red liquid blood in the stool is an alarming symptom that may be caused by numerous diseases. Severe bleeding is often a medical emergency that warrants prompt intervention.

Different Forms of "Blood in the Stool"

There are several forms of blood in stool, which are often described in somewhat confusing terms. Hematochezia refers to frank blood in the stool. Usually the cause of such bleeding lies in the lower gastrointestinal tract. Bleeding from the upper portions of the gastrointestinal tract can result in hematochezia if there is excessive bleeding. However, more commonly upper gastrointestinal bleeding results in black, tarry stool. This is referred to as melena and occurs due to the digestion of blood in the intestine. When there is excessive bleeding from the upper gastrointestinal tract, most of the blood is not digested, and appears in the stool as frank blood. Blood released into the intestine from bleeding in the lower gastrointestinal tract is not fully digested and commonly results in frank blood or hematochezia. Slow bleeding or bleeding from the upper region of the lower gastrointestinal tract may present as melena instead of frank bleeding. Occult bleeding may also occur, in which the blood in the stool may not be visible to the naked eye, but will be detectable with laboratory tests. This bleeding often results in anemia due to long standing slow blood loss through the stool. Another type of bleeding is rectorrhagia, in which the rectum is the source of bleeding. Blood is passed even in the absence of defecation. The table given below summarizes these four conditions.





Lower GI tract usually

Frank blood in the stool


Upper GI tract usually

Black, Tarry stools



Passage of blood not associated with defecation

Occult Blood

Minor bleeding anywhere

Not visible to naked eyes. Detectable by laboratory test.

General Approach to Management

Management of blood in stool depends upon the cause of the bleeding and its severity. Excessive, life-threatening bleeding must be treated immediately, whereas less severe bleeding should be evaluated by diagnostic procedures (colonoscopy, endoscopy, angiography, etc.) to determine its cause. Then appropriate treatment can be addressed. Sudden onset bleeding usually stops spontaneously. Blood in the stool is one presentation of colon cancer, so neoplastic lesions must be ruled out.

Causes of Hematochezia

In nearly nine out of ten cases of hematochezia, the source of bleeding lies in the colon. The amount of bleeding is variable. Severe life-threatening bleeding may occur in conditions such as diverticular disease and vascular malformations, whereas hemorrhoids may only cause minor bleeding. As previously mentioned, bleeding from the upper gastrointestinal tract causes black tarry stools called melena. However, if the bleeding is substantial, upper GI bleeding can also result in frank blood in the stool. Some common causes of this include peptic ulcer disease, Mallory-Weiss syndrome (tear at the stomach-esophagus junction), arteriovenous malformations, gastroesophageal varices (dilated veins due to portal hypertension), gastritis, duodenitis, and esophagitis. This severe blood loss might be life threatening, so patients should be rushed to the hospital.

The most common causes of blood in the stool are listed in the table below. The lower gastrointestinal bleeding in these cases appears as frank blood in the stool.

Table: Common causes of Frank Blood in Stool (Hematochezia)



Diverticular Disease

Out pocketing of inner layers of wall of colon through defects in the external muscle layer.

Colon Cancer

Uncommon but most important cause

Ischemic Colitis

Inflammation of colon caused by inadequate blood supply

Anorectal Disease

Hemorrhoids, Condyloma acuminata, Rectal Prolapse, Anal Fissures

Inflammatory Bowel Disease

Ulcerative Colitis and Crohn’s Disease

Radiation colitis/proctitis

Inflammation of colon/rectum caused by radiotherapy

Infectious Colitis

Inflammation of colon due to infection


Abnormal growth of tissue. Bleeding can also occur after surgical resection of polyps


Vascular malformations or dilation of the blood vessels in the walls of intestines.


In nearly 1/4th of cases, no source of bleeding can be identified.


Diverticular diseases are responsible for nearly one-third of cases involving frank blood in the stool. Although diverticular disease is very common, only 3-15% of the people with diverticulosis will present with blood in stool. Diverticular disease can be confirmed by a colonoscopy. There are many treatment options. If bleeding site is identified by a colonoscopy, local injection of epinephrine or electrocautery can be used to control the bleeding. If these methods fail to control bleeding or if it recurs, surgical resection of the colon can be performed.

Blood in the Stool and Cancers

Colorectal cancers are rare causes of blood in the stool, but they are a very significant cause to consider, as it is entails a poor prognosis. Blood in the stool might be the earliest and only symptom of colon cancer in its earliest stages. The bleeding occurs occasionally and slowly and is not usually associated with pain. A colonoscopy is used to rule out colorectal carcinomas and biopsies are taken of suspicious lesions. Massive bleeding can also occur with colonic cancers.

Colitis: Inflammation of the Colon

Inflammation of the colon can be caused by many conditions including infections, radiotherapy, ischemia (inadequate blood supply), and inflammatory bowel diseases (Crohn's Disease and Ulcerative Colitis). Amongst inflammatory bowel diseases, Ulcerative Colitis most commonly presents with blood in the stool (compared to Crohn's disease). Crohn's disease rarely causes frank blood in the stool, but stool tests positive for occult blood in patients suffering from this condition. Individuals with inflammatory bowel diseases might have other symptoms, such as frequent diarrhea, abdominal pain, abdominal cramping, feeling of incomplete defecation (called tenesmus), etc. Infectious colitis generally causes bloody diarrhea. Infections with various bacteria including Escherichia coli, Salmonella, Shigella, Campylobacter, Clostridium difficile, etc. can cause infectious colitis. Cytomegalovirus can cause blood mixed diarrhea in immunocompromised persons (such as those with AIDS). Clostridium difficile colitis occurs after the use of antibiotics. With the increasing use of radiotherapy for treatment of various abdominal and pelvic cancers, radiation colitis/proctitis has become a common cause of lower GI bleeding that results in blood in the stool. Often the affected person has other symptoms including tenesmus, diarrhea, pain, and cramping. Various non-surgical treatment options are available for these conditions, which depend on the cause. Mesenteric artery ischemia can result in ischemic colitis, in which the affected person has bloody diarrhea and abdominal pain. This may require urgent surgical intervention.

Other Conditions

Anorectal conditions like internal hemorrhoids, anal fissures, rectal prolapse, and the sexually transmitted disease condyloma acuminata may also result in blood in the stool. Hemorrhoids are the most common cause, but immense bleeding is very rare. The bleeding associated with internal hemorrhoids is usually painless, whereas the bleeding associated with anal fissure is quite painful.

Polyps are abnormal tissue growth from the wall of the colon. Polyps themselves can cause lower gastrointestinal bleeding and blood in the stool, but more commonly, bleeding occurs when polyps are surgically removed (polypectomy).

Angiodysplasias or arteriovenous malformations (AVMs) are degenerative conditions characterized by dilation of the blood vessels in the intestinal walls. AVMs may cause massive bleeding occasionally, which may be life threatening. As with diverticular disease, various non-surgical options are initially attempted before opting for segmental resection of the intestine.

In nearly 1/4 of the cases of blood in the stool, no cause is found, even after thorough evaluation. Often these are those cases in which the hematochezia has resolved spontaneously. Ruling out any cancerous condition is critical.