(Note: For a more recent update on this topic, see the article in our May 2005 newsletter.)
Dr. Swafford's presentation at our Feb 16 meeting highlighted capsule endosccopy as a major advance in diagnosing problems of the small intestine. This test, which involves swallowing a capsule containing a tiny camera, is non-invasive and produces more usable images than previously available methods such as push enteroscopy (a more conventional endoscopic exam that often reaches only a small fraction of the way through the small intestine) and the small bowel follow-through (an X-ray exam of the small intestine).
The device at the heart of capsule endoscopy is called the M2A capsule -- a seemingly high-tech acronym that actually stands for "mouth to anus." It's about the size of a large vitamin capsule. To be more precise, it measures 11 mm in diameter by 26 mm in length and is quite a marvel of miniaturization, including a light source, camera, radio transmitter and batteries.
Aside from the initial act of swallowing the capsule, the test involves no discomfort to the patient, as the capsule advances painlessly through the digestive system, propelled only by natural peristalsis, and there is no need to pump air into the intestine as in more conventional endoscopy.
In preparation for the test, a patient might be told to fast for 10 hours. At around 7 or 8 am, the patient comes to the medical center and swallows the capsule. Sensors are taped to the patient's skin and connected to a recording unit worn around the patient's waist. The patient is then free to leave the medical center and go about his/her business for the next 8 hours while data is recorded. Finally, the patient returns the recording unit to the medical center. No attempt is made to retrieve the capsule, which is designed for only one use and is excreted normally after passing through the digestive system. (The capsule itself doesn't store any images and has battery life of around 8 hours.)
Images recorded by this system can resolve objects as small as 0.1 mm, which is fine enough to see the villi in the small intestine; i.e., the tiny hairlike structures that absorb nutrients. The images are perhaps most useful for locating sources of occult bleeding, but can also help in diagnosing Crohn's disease, Celiac disease, and other disorders.
The purpose of capsule endoscopy is to examine the small intestine. Occasionally, it also produces useful images in other parts of the digestive system such as stomach or large intestine. But due to the size of those organs, the capsule tumbles around in them and therefore cannot image them systematically.
An interesting point: Due to tumbling of the capsule in the stomach, its camera may be randomly pointing forward or backward when the capsule enters the small intestine. Fortunately, the images are just as useful either way.
I am personally somewhat concerned about usability of this procedure in ileostomates: Would the capsule pass easily through the stoma after transiting the intestine, or might it get stuck behind the stoma or abdominal wall? Dr. Swafford didn't seem very concerned about this danger. Still, it seems to me that the capsule's 11 mm diameter is pretty big compared with the size of many ileostomy stomas, and I wonder how often the method has been tested on ileostomates. (Colostomates would have less to fear than ileostomates because colostomy stomas are usually bigger than ileostomy stomas.)
The M2A capsule was developed by an Israeli scientist and is produced by the company Given Imaging which is headquartered in Israel although it has many other offices around the world. The system has been approved by the FDA for use in the United States.
Dr. Swafford noted that Stillwater Medical Center was the first hospital in this area to offer capsule endoscopy, and he has personally done around 30 of them. He pointed out that although images from the capsule are superior to data obtained from small bowel follow through X-ray, he normally does an X-ray study first because it's considerably less expensive and sometimes produces good enough results to resolve a problem.
One current problem in capsule endoscopy is figuring out the capsule's exact location while sending any particular images. Dr. Swafford said that with the equipment he has currently, he gauges the capsule's position simply by tracking how much time it takes to progress between intestinal landmarks. This may not be an accurate measure of position because the capsule's speed isn't necessarily uniform. There is now an "M2A Plus" capsule with improved localization capability, although this remains an area of active research.
Another difficulty in using the capsule system is the amount of time it takes a gastroenterologist to analyze the results. The system may produce around 55,000 images, and the gastroenterologist really needs to view all of them or he may miss a key finding. Dr. Swafford says it takes him up to 2 hours to interpret one of these tests.
For more information about the M2A capsule, assuming you have Internet access, see the Given Imaging web site at www.givenimaging.com.
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Content last revised 2005-05-02