The endoscope is used to help determine the cause of small bowel bleeding. The endocapsule is about the size of a large pill (1-1/8 inches long and 3/8 inches wide or 26 mm x 11 mm). It is composed of a battery with an 8-hour lifespan, a strong light source, a camera, and a small transmitter. Once you swallow the capsule, it begins transmitting images of the inside of your esophagus, stomach and small bowel to a receiver you wear. The capsule takes two pictures per second, for a total of approximately 55,000 images. After 8 hours, you return the receiver to the doctor who downloads the images to a computer and looks for abnormalities that are possible sources of bleeding. The capsule passes through your colon and is eliminated in the stool as waste.  

Like x-rays, the capsule is purely diagnostic and cannot be used to take biopsies, apply therapy, or mark abnormalities for surgery. It also cannot be controlled once it has been ingested, so that if it has passed a suspicious abnormality, its progress cannot be slowed to better visualize the area. Despite these limitations, capsule endoscopy is frequently the test of choice for finding a source of small bowel bleeding if standard endoscopy has failed to do so.