Lower gastrointestinal (GI) bleeds occur when any part of the lower digestive tract bleeds. This may happen as a result of an injury, ulceration, or inflammation. They can range from minor to severe.

In many cases, lower GI bleeds stop on their own. But severe, persistent, or recurring bleeding can become serious.

This article discusses what a lower GI bleed is, the symptoms, when to seek help, causes and treatments, risk factors, potential complications, and recovery.

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The GI tract, or digestive tract, includes the organs and structures that the body uses to digest and excrete food. A lower GI bleed occurs when any part of the lower digestive tract bleeds.

The lower GI tract includes:

  • most of the small intestine
  • the large intestine, or colon
  • the rectum
  • the anus

About 20–33% of all GI bleeding events in Western countries occur in the lower GI tract.

GI bleeds can be acute or chronic. Acute bleeding can be sudden and severe, while chronic bleeding lasts for a longer period of time and may cause less obvious symptoms.

People can also have upper GI bleeds, which occur anywhere between the esophagus and the first segment of the small intestine, which is known as the duodenum.

Lower GI bleeds can cause several noticeable symptoms, including:

  • bright red blood drops, smears, or clots in the stool
  • abdominal cramps or pain
  • faintness and dizziness
  • unexplained exhaustion or weakness
  • unusual paleness
  • shortness of breath

This is different from an upper GI bleed, which is more likely to cause black, tarry stools, vomit that contains blood or resembles coffee grounds, or sudden, severe bleeding.

People with acute GI bleeding may also experience symptoms associated with severe blood loss, such as shock. The symptoms of shock include:

People with chronic GI bleeds may not notice many symptoms at all. In these cases, blood may only be detectable in the stool or vomit using a lab test. Over time, chronic GI bleeds can lead to anemia.

Anyone with sudden and unexplained blood in their stool or vomit should seek medical attention.

If bleeding is severe or continuous, or a person has symptoms of shock, call 911 or go to the nearest emergency room.

Anyone who experiences sudden heart rate changes, loss of consciousness, changes in blood pressure, or changes in skin color or temperature also require emergency care.

Any condition that causes damage to the digestive tract can potentially cause bleeding. Some of the most common causes include:

Hemorrhoids and anal fissures

Hemorrhoids, or piles, are inflamed, swollen veins around the anus or in the lower rectum. They may form under the skin or inside the lining of the anus or lower rectum.

People can also develop anal fissures, which are cracks or tears that extend into the anal canal.

Both hemorrhoids and anal fissures are common and will usually heal on their own. People can manage them at home by:

  • increasing fiber intake in the diet
  • staying hydrated with water
  • taking an over-the-counter (OTC) stool softener
  • avoid straining during bowel movements
  • using moist towelettes or cotton wool instead of dry toilet paper to reduce irritation
  • taking a sitz bath by sitting in a tub of warm water
  • OTC hemorrhoid creams

If an OTC hemorrhoid cream does not help after 1 week, it is best to speak with a doctor.

Learn more about the treatments and causes for hemorrhoids.

Medications

Antithrombotic medications, which reduce the formation of blood clots, can also cause GI bleeding. These include medications such as:

Doctors often prescribe these medications for people with heart arrhythmias, a history of blood clots, or clotting disorders. People may also take them following the fitting of a stent or metallic valve.

A doctor can determine if a medication could be causing GI bleeding and advise the best course of action. People should not adjust their dosage or stop taking the medication without a doctor’s input, as this could be dangerous.

Diverticulosis and diverticular bleeding

Diverticulosis is a chronic condition that occurs when tiny sacs or pouches form in the colon and push outward through weakened parts of the colon wall. Sometimes, the blood vessels in these pouches can become injured. This increases the likelihood of diverticular bleeding.

Diverticular bleeding is distinct from diverticulitis. Diverticulitis occurs when fecal matter becomes lodged in a diverticulum, causing inflammation but not bleeding. It is also rare for diverticulitis to occur alongside bleeding.

Diverticular disease is responsible for an estimated 40% of all lower GI bleeds and often causes no noticeable symptoms other than red blood in the stool.

To treat diverticular bleeding, doctors find the site of bleeding using a colonoscopy, angiogram, or CT scan. If they cannot stop the bleeding, some people may require a colon resection, which involves removing the damaged part of the intestine.

Bleeding disorders

Bleeding disorders cause problems with blood clotting, meaning a person can bleed excessively if they become injured. Sometimes, this may result in lower GI bleeds.

The most common bleeding disorder is Von Willebrand’s disease. The symptoms include:

  • unexplained or easy bruising
  • heavy periods
  • excessive bleeding from small injuries
  • frequent nosebleeds that may be difficult to stop
  • blood in the stool or urine
  • anemia

There is no cure for bleeding disorders, but medications may help reduce the symptoms. For example, certain hormonal medications can increase clotting factors in the blood, while iron supplements can help prevent anemia.

Colitis

Colitis refers to inflammation in the large intestine. This can be caused by:

  • infections
  • a lack of blood flow
  • inflammatory bowel disease (IBD)

IBD includes Crohn’s disease and ulcerative colitis. Crohn’s disease can cause inflammation in any part of the digestive tract, but tends to affect the small intestine and the start of the large intestine.

The treatment for colitis depends on the cause. People with infections may require antibiotics. Those with IBD may require more long-term treatment in order to control their symptoms. This could include:

  • anti-inflammatory medications, such as steroids
  • immunosuppressants, immunomodulators, and biologics
  • surgery to remove affected parts of the GI tract

Learn more about the symptoms and treatments for IBD.

Angiodysplasia

Angiodysplasia refers to abnormally large or swollen blood vessels in the digestive tract. These blood vessels can rupture and bleed. People with angiodysplasia can also develop lesions in the colon.

Angiodysplasia many not cause many symptoms aside from rectal bleeding, and so may be difficult to detect. Scientists do not know what causes it.

Treatment involves a doctor finding the source of the bleeding and then closing the damaged blood vessel. They may do this via an angiography, which can administer medication to close the bleed. Doctors can also cauterize the vein to close it. In severe cases, a person may need surgery.

Polyps

Polyps are small growths that protrude from the lining of the colon and rectum. Many polyps are noncancerous, though some may become cancerous over time.

Doctors can surgically remove polyps to reduce the risk of cancer.

Learn about the types of colon polyp and their treatment.

Colorectal cancer

Cancer occurs when cells begin to abnormally grow and divide, often forming masses known as tumors. Rectal cancer occurs in the rectum, while colon cancer occurs in the large intestine. Together, doctors refer to these conditions as colorectal cancer.

In most cases, doctors treat colorectal cancer through surgery to remove abnormal growths and, if necessary, nearby lymph nodes. Chemotherapy and radiation may be necessary before or after surgery, depending on the severity and extent of the cancer.

Learn more about the symptoms and treatments for colorectal cancer.

Factors that may increase the risk of lower GI bleeding include:

  • age
  • overuse of nonsteroidal anti-inflammatory drugs, which can irritate the lining of the GI tract
  • chronic constipation, which may lead to straining and hemorrhoids
  • family history of conditions that damage the lower GI tract, such as IBD
  • blood or bleeding disorders, or a family history of these disorders
  • activities that could potentially cause rectal tears, such as anal sex

Learn more about the potential risks of anal sex and how to avoid them.

Lower GI bleeds may cause complications if the bleeding is severe or left untreated. Usually, this is the result of blood loss.

The potential complications include:

For this reason, it is important to speak with a doctor about any unexplained blood that appears in the stool or vomit, as it may signal a condition that requires treatment.

Lower GI bleeds are often less serious than upper GI bleeds, with only 4% of people hospitalized with the condition dying. Often, these deaths are related to other conditions rather than the bleed itself.

More than 80% of lower GI bleeding events resolve on their own, but this can depend on the cause. Bleeding as a result of chronic conditions, such as diverticulitis, can recur.

How long it takes to recover from GI bleeds depends almost exclusively on the cause, as well as how early a doctor diagnosed and treated it. Minor cases may heal fairly quickly, but severe bleeding or bleeds that result in complications may take longer.

For people who experience bleeding due to chronic health conditions, long-term dietary and lifestyle changes may be necessary to reduce irritation and inflammation inside the digestive tract. Gastroenterologists and dietitians may be able to help people adapt and manage their symptoms.

Lower GI bleeds are the result of bleeding between the small intestine, large intestine, rectum, or anus. The potential causes include hemorrhoids and fissures, fistulas, and IBD. In some cases, it can be a symptom of polyps or cancer.

If a person has sudden, severe, or frequent blood in their stool or vomit, they should seek immediate medical attention.