Wireless capsule endoscopy is a system that miniaturizes technologies into a capsule containing a light source, image sensor, transmitter, and power source (battery). The pill is somewhat large but successfully swallowable by most patients. As the capsule travels through the GI tract, it takes two pictures per second, sending images to a computer. The signal is received by an array of sensors that are attached by a special belt to the abdomen. The sensors are connected to a portable computer worn on the belt, similar to a Holter monitor used for monitoring cardiac rhythm. Peristalsis moves the capsule through its journey during which time the patient carries on a “normal” day. After 8 hours, the sensors, belt, and computer are removed. The information is downloaded into a computer for processing and viewing the pictures. The images obtained are high quality with resolution that is impressive. There are no controls to steer, slow down or speed up the capsule during passage, thus a small lesion may be missed or seen only on a few images if the capsule is traveling rapidly at that time.
The capsule is designed for imaging the small bowel. It does not image the colon at this time. Other current techniques to evaluate the small bowel have limitations.
Endoscopically, a pediatric colonoscope can be used to reach the distal duodenum and most proximal jejunum (first parts of the small bowel). A fiberoptic enteroscope, a special longer scope available in Cincinnati at Christ Hospital, can probe considerably deeper into the small intestine but still sees only about half of the approximately 20 feet of it. Advantages of scope techniques are control and the ability to biopsy and cauterize lesions. Radiographically, the small bowel can be imaged by barium (small bowel follow through or enteroclysis). Flat or small lesions are difficult to see. Arteriovenous malformations (AVM), a common cause of chronic GI bleeding, are notoriously difficult to find in the small bowel. They are flat and not visualized on small bowel X-rays. They can also develop in the distal small bowel and thus not be reachable by scopes.
The primary indication for capsule endoscopy is evaluating obscure/occult GI bleeding. These patients have anemia, recurrent visible or occult GI bleeding and negative EGD and colonoscopy, implying a small bowel source. Within the small bowel, tumors, arteriovenous malformations (AVM), ulcers, inflammation (Crohn’s disease and others) can be visualized by capsule endoscopy.
Chronic diarrhea and other symptoms suggestive of small intestine inflammation (Crohn’s Disease and others) can be accurately assessed with capsule endoscopy.
The patient fasts beginning 10 p.m. the night before. After arriving at the endoscopy center and prepared for the test, the battery is activated simply by taking the capsule out of the package which removes it from a magnet, which kept the switch off. The capsule is ingested in the morning and clear liquids are allowed for the next 2 hours – solid food could cloud the lens and obstruct the view. The patient returns 7-8 hours later (or the next day) and the sensor array and belt are removed. The information is downloaded by the endoscopy nurse into a computer. The images are viewed and a report is prepared. The “video” created by stringing photos together can be viewed from one frame at a time to 25 frames per second. It usually takes about 1 hour to transit thru stomach and 4-5 hours thru small bowel into the colon.
CLAIMS AND REALITY
No discomfort or complications?
For some, just swallowing this rather large pill may be briefly uncomfortable. There is no sensation associated with the capsule as it passes down the GI tract. The capsule could lodge itself at an area of narrowing producing a bowel obstruction, requiring surgery.
This technique is considered non-invasive and does not even require an I.V.
In patients with occult or microscopic GI bleeding who have had negative evaluations of the upper GI tract and the colon, capsule endoscopy has found abnormalities in the small bowel in 60%.
Capsule endoscopy currently does not visualize the colon. Future models might allow visualizations from both ends of the capsule, improving ability to peer behind folds etc. We look forward to potential future uses in the colon (and elsewhere).