Overview
- What is the small bowel?
The small bowel, also called the small intestine, is the longest part of the digestive tract. It is called "small" because it is thin or narrow compared to the "large" bowel (colon), not because it is short. In fact, the small bowel is about 14 feet long. This is much longer than the large bowel. The main job of the small intestine is to absorb nutrients and water from food.
- What is small bowel bleeding?
Bleeding originating in any part of the small intestine, from the beginning (duodenum) to the end (also called terminal ileum) is defined as small bowel bleeding. About 5 out of 100 cases of intestinal bleeding come from the small bowel. The most common cause is abnormal blood vessels, called arteriovenous malformations or AVMs. These cause 30 to 40% of small bowel bleeds and are the main source of bleeding in people over age 50. Other causes include tumors (cancerous and non-cancerous), polyps, Crohn’s disease, and ulcers caused by medications such as NSAIDs (aspirin, ibuprofen, etc.).
Many tests can be used to find and treat the bleeding, including endoscopy, x-ray studies, and video capsule endoscopy (pill camera). AVMs can often be treated during an endoscopy procedure. Tumors can be biopsied and their location marked using endoscopy, but surgery may be required to take them out. Other conditions, such as Crohn’s disease, are treated with medications or surgery.
Symptoms
- What are the symptoms of small bowel bleeding?
Bleeding from the small bowel can be slow or fast. Slow bleeding may cause anemia or low blood count but is often invisible (i.e. the stool looks normal). Symptoms can include tiredness and shortness of breath, but many people have no symptoms. Fast bleeding is called a hemorrhage. People may see blood in the stool or have black, tarry, sticky stools.
Causes
- What causes small bowel bleeding?
The most common cause is abnormal blood vessels, called arteriovenous malformations or AVMs. These cause 30 to 40% of small bowel bleeds and are the main source of bleeding in people over age 50. These abnormal blood vessels are also known as angioectasias or angiodysplasias. AVM’s are more common in people who have chronic heart, lung (COPD), liver or kidney disease and in smokers; in rare cases, multiple AVM’s can be the result of a genetic condition. The reason they bleed is because they have very thin walls which break with minimal contact. Other causes of small bowel bleeding include tumors (cancerous and non-cancerous), polyps, Crohn’s disease, and ulcers caused by medications such as NSAIDs (aspirin, ibuprofen, etc.).
Risk Factors
- What are the risk factors of small bowel bleeding?
AVMs become more common as people age and are associated with other medical problems, such as chronic heart, lung, liver or kidney disease. Nonsteroidal anti-inflammatory drugs (NSAIDS) like ibuprofen or aspirin can cause ulcers in the small bowel. People who take blood thinners tend to have more severe bleeding regardless of cause.
Diagnosis
- How is small bowel bleeding diagnosed?
There are many tests to check the small bowel. Usually, the first step is endoscopy and/or enteroscopy (using a long flexible tube with a light and a camera on the end). If bleeding is not found, a wireless capsule endoscopy (pill camera) can be performed, X-ray, computed tomographic scan (also known as a CT or CAT scan) of the small bowel may be used in certain cases. Deep small bowel enteroscopy with special scopes can be performed. Intraoperative enteroscopy is rare and requires surgery. This is usually only done if the other tests do not find the bleeding.
- How does endoscopy and enteroscopy test for small bowel bleeding?
Endoscopes and enteroscopes are long, thin, flexible tubes with a light and a camera on the end that are passed under sedation into the small intestine. When the endoscopist finds a bleeding source, they are able to pass special equipment through channels in the scope and intervene to stop the bleeding, take biopsies, sometimes remove tumors or polyps or mark the site of a tumor with a tattoo for later surgery.
- How do x-rays test for small bowel bleeding?
There are three x-ray tests commonly used to evaluate the small bowel – small bowel follow-through, enteroclysis, and CT enterography. The most common test is CT enterography.
- Small bowel follow-through: the patient drinks a white, chalky fluid called barium and x-rays are taken. The test is good for large abnormalities but can miss many smaller ones.
- Enteroclysis: a tube is placed through the nose into the small intestine and contrast is injected through the tube. This is supposed to be more accurate for detecting abnormalities compared with a small bowel follow-through. Both are very rarely performed nowadays as they have been replaced by CT scans.
- CT Enterography: The patient drinks an oral contrast solution while also receiving intravenous (IV) contrast. Then numerous, very detailed pictures are taken. This allows for a detailed inspection of the lining of the small bowel.
These tests can sometimes find bleeding sources that are out of reach of a standard enteroscope. These studies cannot detect AVMs, and if an abnormality is seen, there is no way to immediately treat to stop the bleeding, to take biopsies to confirm a diagnosis, or to mark the location of the lesion with a tattoo. In addition, some patients are allergic to the IV contrast that is used as part of the CT scan.
- How does capsule endoscopy test for small bowel bleeding?
During capsule endoscopy, a patient swallows a camera that is the size of a large pill. The pill moves through the bowel and takes thousands of pictures. The pictures are transmitted to a receiver and converted into a video which can be reviewed by a clinician, typically a few days later. The patient passes the capsule in the stool, and it can be flushed down the toilet. There are versions of capsules that store the entire gallery of pictures inside them and need to be retrieved with a magnetic rod and sent to a processing facility. The advantage of these capsules is that they don’t require trained staff on site and can be performed in the office.
The capsule is generally safe and easy to swallow. Rarely, the capsule can get stuck in the small intestine. This may happen in patients who have had small bowel surgery or in patients with small intestine narrowing or strictures from Crohn’s disease. If the capsule gets stuck, it can sometimes be removed with endoscopy, but surgery may be needed. If the capsule becomes stuck, there is a good chance that it is stuck at the place where the bleeding is coming from, so the procedure to get the capsule (endoscopy or surgery) could treat the bleeding site at the same time. In about 15% of tests, the capsule battery runs out before the capsule reaches the colon. If this happens, the capsule study may need to be repeated.
Like x-rays, the capsule cannot be used for interventions, but only to visualize abnormalities. The capsule cannot be controlled once it has been swallowed. The capsule cannot move back and forth to reexamine a suspicious area. Despite these limitations, capsule endoscopy is frequently the test of choice for finding a source of bleeding if standard endoscopy is negative, because it has the highest yield in detecting small bowel bleeding. As opposed to other procedures, patients don’t need to stop their blood thinners prior to swallowing the capsule.
Overall, in patients with invisible bleeding, capsule endoscopy finds a cause for bleeding in up to 2/3 of patients. In cases where patients see blood in the stool, the results are variable. The closer the capsule is performed to the time of bleeding, the higher the yield; if a capsule is performed at the time of bleeding, the cause can be found in up to 90% of patients.
- What is deep enteroscopy and why would it be used?
If a problem is found deep in the small intestine where regular scopes cannot reach, doctors may use small bowel enteroscopy, also called deep enteroscopy. Small bowel enteroscopy uses balloons attached to the scope to help the scope stabilize as it moves through the long, twisty small bowel. The scope can be placed through the mouth, or through the anus. By doing both procedures, doctors can see most or all of the small intestine. The test usually takes more than an hour, much longer than a regular endoscopy. Because it is more complex, it is usually done only after a problem has been found on another test, like a capsule endoscopy. If bleeding is found, doctors can treat bleeding, take biopsies, or mark an area for surgery.
- What is intraoperative enteroscopy and why would it be used?
In some cases, surgery is needed. Intraoperative enteroscopy is done in the operating room while the patient is asleep, under general anesthesia. The surgeon and GI doctor work together. The scope may be placed through the mouth or through an opening made in the small intestine. This allows doctors to look at the entire small intestine. Intraoperative enteroscopy allows the doctor to treat the cause of bleeding if it is found. Because this is a surgery, this is only used if all other tests and treatments have not worked. This procedure can treat the bleeding problem in approximately 70% of patients.
Treatment
- How is small bowel bleeding treated?
Treatment depends on the cause of the bleeding. AVMs (abnormal blood vessels) can be treated using cautery. If bleeding is found by capsule endoscopy or CT enterography, treatment may require standard endoscopy, deep enteroscopy, or intraoperative enteroscopy depending on the location of the bleeding site. In rare cases, a segment of small bowel may need to be removed surgically. Some cases of bleeding from AVM’s that persist or do not respond to endoscopic therapy, can be treated with medications. In other cases, when all therapies fail, supportive therapy (periodic infusions of iron or blood transfusions) may be required. Bleeding from AVM’s often recurs after endoscopic treatment because the underlying cause of AVM’s, has not or cannot be eliminated.
Polyps can often be removed with an endoscope. Sometimes surgery is needed if the polyp cannot be fully removed with an endoscope. Tumors, both cancerous and non-cancerous, may need surgery to remove if they are causing bleeding. Other causes of small bowel bleeding, like small intestine ulcers due to Crohn's disease, are usually treated with medications. When the ulcers are caused by medications such as NSAIDs (aspirin, ibuprofen, naproxen, diclofenac), the only intervention that works is stopping the offending drug.
Author(s) and Publication Date(s)
John R. Saltzman, MD, FACG, and Richard S. Tilson, MD, Gastroenterology Consultants of Greater Lowell, North Chelmsford, MA – Published June 2004.
John R. Saltzman, MD, FACG, and Anne C. Travis, MD, MSc, FACG, Brigham and Women's Hospital, Harvard Medical School, Boston, MA – Updated February 2009. Updated December 2012.
Michael Chiorean, MD, FACG, Swedish Medical Center and Ann Flynn, MD, FACG, University of Utah School of Medicine - Updated April 2026.