Intestinal bleeding, including from the small bowel, occurs when an abnormality on the inner lining begins to bleed. It may bleed slowly (causing anemia or low blood count) or may cause a hemorrhage. Fortunately, only 3-5% of all gastrointestinal bleeding comes from the small bowel, and most of these abnormalities lie within reach of the standard endoscope used to evaluate the stomach and upper small bowel. An endoscope is a tube instrument with a light and camera at one end passed through the mouth) after receiving a sedative. A longer instrument called an enteroscope can reach further into the small bowel.
Determining the source of gastrointestinal (GI) bleeding that originates in the small bowel (the area of the intestine between the stomach and the colon) is one of the major diagnostic challenges facing gastroenterologists. Many small bowel causes of blood loss go undetected because the small bowel is long and hard to reach and therefore difficult to evaluate. The small bowel is constantly contracting and relaxing making visualization impossible for more than a few seconds. In addition the small intestine is much more mobile than either the stomach or colon, making endoscopy much more difficult. X-ray studies may be unable to pinpoint exact locations of abnormalities so that if masses or bleeding lesions are found, their location is difficult to accurately describe to the surgeon for removal. Finally, the small bowel is more then 17 feet long, which is much longer than any of the instruments currently available.
The causes of bleeding in the small bowel are different from those in the colon or the stomach. The most frequent causes of large bowel (colon) bleeding are polyps, diverticulosis or cancer. Upper GI (esophagus, stomach or duodenum) bleeding sources are most frequently associated with ulcers. However, unlike the colon and the upper GI tract, 70-80% of small bowel blood loss that is significant enough to warrant investigation is caused by abnormal blood vessels that lie within the wall of the small bowel. These abnormal blood vessels called AVMs (arteriovenous malformations) are invisible to standard X-rays. Other, less common causes of small bowel bleeding include both benign (non cancerous) and malignant (cancerous) tumors, Crohn’s disease (an inflammatory bowel disease) and ulcers.
Once swallowed, the capsule begins transmitting images of the inside of the esophagus, stomach and small bowel to a receiver worn by the patient. After 8 hours the patient returns the receiver to the doctor who loads the information into a computer and then can review in detail the 8 hours of pictures of the capsule passing through the intestine looking for abnormalities that are possible sources of bleeding. The patient passes the capsule through the colon and it is eliminated in the stool and discarded. The capsule is safe, easy to take and has had only rare reported side effects. However, the capsule can get stuck in the small intestine if there has been prior abdominal surgery causing scarring or due to any other condition that causes narrowing of the small intestine. If the capsule becomes stuck, surgical removal is necessary.