Searching For the Leak.... What if you were a plumber and couldn't find the leak? That is the situation that sometimes frustrates doctors asked to evaluate a patient with signs of iron deficiency anemia due to blood loss. There are many types of anemia. Iron deficiency anemia is a common type and most often occurs in pregnant women or menstruating women due to the monthly loss of blood. But when significant iron deficiency anemia occurs in women after the age of menopause or in men, it is often a sign of the loss of blood from somewhere else - usually the digestive tract. This blood loss may be very gradual and not visible to the patient. But over time, the continued loss of blood can deplete the body of iron and anemia develops.
If a doctor suspects that anemia is due to intestinal bleeding, special tests are usually ordered to help the doctor "find the leak." This is a bigger task than most people realize since the average adult digestive tract is approximately 30 feet in length. The top 4 feet includes the esophagus (foodpipe) and stomach and first portion of the small intestine, called the duodenum. The bottom 6 feet makes up the colon and rectum. In between, lies the rest of the 20 feet of small intestine where the process of digestion actually occurs.
Scope Tests
In this situation, one of the first diagnostic studies ordered are
special "scope" tests of the digestive tract. Gastroscopy is used to check the first 4 feet of the upper
digestive tract and colonoscopy to evaluate the colon and rectum. As you
can see, most of the 20 feet of small intestine lies beyond the reach
of these two studies. Fortunately, most bleeding problems seem to
occur in the area than can be "scoped" and the source of bleeding is
usually found and treated. Common problems would include hiatal
hernia, gastritis, ulcers, polyps, and, sometimes, stomach or colon
cancer.
The Small Intestine - Uncharted Territory
What if a patient had severe iron deficiency anemia and scope
tests of the stomach and colon are normal? It is not uncommon for
doctors to evaluate a patient with unexplained anemia and neither
gastroscopy nor colonoscopy scope examinations reveal the diagnosis. By
a process of elimination, it then becomes likely that the source of
bleeding lies somewhere in-between - below the reach of the
gastroscope and above the reach of the colonoscope - in the 20 feet of
small intestine. How then is this area examined?
Well, not very well. Gastroscopy and colonoscopy cannot reach this far. Contrary to popular belief, special imaging studies like CT scan or MRI are not useful in this circumstance. X-rays of the small intestine can be performed after drinking a chalky solution of barium. Called a small bowel series, this test has been available for many years, but has a limited accuracy. X-rays are still only shadow pictures and do not view the object itself like a camera.
Why not use a longer scope?
Since scope tests were first invented, doctors have wanted to be able
to visualize the entire gut - all 30 feet. But, a direct view of the
small intestine has remained elusive. Attempts have been made to
develop longer endoscopic instruments. This technique called push
enteroscopy has had only limited success. The longer instruments are
difficult to control and manipulate and are hard to maintain. The
accuracy of push enteroscopy is still limited since even in the best
of hands the entire small intestine is not visualized.
The Given Video Capsule - Hope For the Future
In 1981, an Israeli physician, Dr. Gavriel Iddan, began development of
a video camera that would fit inside a pill. Technology was not ready
and the idea was put on hold. It took 20 years for technology to
catch up with Dr. Iddan. In 2001, the FDA approved the Given Diagnostic Imaging
System. This may sound like science fiction, but this 11 x 26 mm
capsule weighs only 4 gms (about 1/7th of an ounce) and contains a
color video camera and wireless radiofrequency transmitter, 4 LED
lights, and enough battery power to take 50,000 color images during an
8-hour journey through the digestive tract. About the size of a large
vitamin, the capsule is made of specially sealed biocompatible
material that is resistant to stomach acid and powerful digestive
enzymes. Another name for this new technique is Wireless Capsule
Endoscopy.
Patients report that the video capsule is easier to swallow than an aspirin. It seems that the most important factor in ease of swallowing is the lack of friction. The capsule is very smooth, enabling it to slip down the throat with just a sip of water. After the Given M2A capsule is swallowed, it moves through the digestive track naturally with the aid of the peristaltic activity of the intestinal muscles. The patient comfortably continues with regular activities throughout the examination without feeling sensations resulting from the capsule's passage. During the 8 hour exam, the images are continuously transmitted to special antenna pads placed on the body and captured on a recording device about the size of a portable Walkman which is worn about the patient's waist. After the exam, the patient returns to the doctor's office and the recording device is removed. The stored images are transferred to a computer PC workstation where they are transformed into a digital movie which the doctor can later examine on the computer monitor. Patients are not required to retrieve and return the video capsule to the physician. It is disposable and expelled normally and effortlessly with the next bowel movement.
This technique is very new, but preliminary reports have already demonstrated cases in which the Given videocapsule was able to make a diagnosis not seen by conventional studies. This remarkable device will never be 100% accurate. No medical procedure is. But current estimates suggest an accuracy of about 55%, an improvement over push enteroscopy.