M2A Capsule Endoscopy

Davey R. Deal, M.D., Louis Lambiase, M.D., Jianjun Li, M.D.

 
The M2A (mouth-to-anus) capsule endoscopy (CE) system developed by Given Imaging, Ltd. has provided gastroenterologists with the ability to examine the small intestine as never before. It was approved by FDA in August of 2001 and it is currently available in 33 countries worldwide. CE is being performed by two medical centers in Jacksonville, with forty studies completed at our hospital in the first half of 2002.

The CE is an 11x26-mm capsule that encases a digital camera, light-emitting diodes, batteries, and a transmitter. Images are taken twice-per-second and transmitted to a recording device worn on a belt by the patient. Thousands of images are transmitted to the recording device and then evaluated after the study is completed. It takes approximately two hours for a gastroenterologist to review the series of images produced. The capsule has a gastric transit time of approximately one hour and a small intestinal transit time of three and a half to four hours. Patients swallow the capsule in the morning and wear the recording device for eight hours. They may perform their regular daily activities during the study. The only bowel preparation involved is that the patient cannot eat after midnight the day prior to the study. The capsule is discarded after one use.

The new technology has its greatest utility in the evaluation of obscure gastrointestinal bleeding. Obscure GI bleeding is defined as bleeding of unknown origin that persists or recurs (i.e., recurrent or persistent iron deficiency anemia, FOBT positivity, or visible bleeding) after a negative initial or primary endoscopy (colonoscopy and/or upper endoscopy).1 In approximately 5% of all patients with GI bleeding, no cause for the bleeding is evident even after an extensive workup.2 Twenty-seven percent of patients with obscure GI bleeding have been shown to have lesions in the small bowel.3

Prior to the development of CE, the nonsurgical evaluation of patients with obscure gastrointestinal bleeding was limited to push enteroscopy, Sonde enteroscopy, small bowel follow-through (SBFT) x-ray series, small bowel enteroclysis, technetium 99m-labeled red blood cell scan (TRBC), and angiography. All of these modalities are limited in their sensitivity for small bowel pathology, and they have been especially disappointing in terms of eliciting the etiology of obscure gastrointestinal bleeding.

In a study comparing CE to push enteroscopy to identify beads sewn into the small bowel of canines, the sensitivity of the capsule was 64% compared with 37% for push enteroscopy. 4 In a study in humans comparing CE and push enteroscopy for the identification of a source of obscure gastrointestinal bleeding, CE was superior to enteroscopy in locating a bleeding source. This was due to the limitation of reaching distal small intestine by enteroscopy. In addition, patients preferred the CE and the image quality were judged as good to excellent. A bleeding site was discovered by CE in 64% of patients, and CE found a bleeding source in 5 of 9 patients with normal push enteroscopic exams. 4 Lewis B, Swain P. Capsule endoscopy in the evaluation of patients with suspected small intestinal bleeding, a blinded analysis: the results of the first clinical trial. (Gastrointestinal Endoscopy 2001;53:AB70).

There are several drawbacks to CE. The main drawback is the difficulty in identifying the precise location of pathology when it is found. In May of 2002 Given Imaging announced the release of its new "M2A Plus", which will allow location of small intestinal disease with greater accuracy. The M2A Plus and the accompanying new version of RAPID® software create a graphic representation of a patient's GI tract to more accurately locate the detected pathology. A validation study prepared for the FDA showed that the location determined by the M2A2 system was comparable to the actual location found by fluoroscopy.

Another drawback to CE is the lack of ability to biopsy or treat pathology when it is found. CE is quite expensive, and insurance company reimbursement is poor considering the 1-2 hours required by the physician to review the images for one patient. The M2A CE has provided gastroenterologists the ability to more accurately assess for the presence of small intestinal pathology. Studies thus far indicate that it is more sensitive than other nonsurgical procedures for diagnosing the etiology of obscure gastrointestinal bleeding. The only absolute contraindication for capsule endoscopy is intestinal obstruction. The new technology will likely prove to be of benefit in diagnosing otherwise elusive small intestinal pathology such as undiagnosed small intestinal Crohn's disease and small intestinal tumors not seen with available radiologic imaging techniques. More studies are needed to determine its role in the diagnosis of other gastrointestinal pathologies.

References

  1. Zuckerman G et al. AGA technical review on the evaluation and management of occult and obscure gastrointestinal bleeding. Gastroenterology 118-1 2000.
  2. Lahoti S. The small bowel as a source of gastrointestinal blood loss. Curr Gastroenterol Rep 1999; 1(5): 424-30.
  3. Appleyard M et al. A randomized trial comparing wireless capsule endoscopy with push enteroscopy for the detection of small-bowel lesions. Gastroenterology 2000; 119(6): 1431-8
  4. Lewis B, Swain P. Capsule endoscopy in the evaluation of patients with suspected small intestinal bleeding, a blinded analysis: the results of the first clinical trial. Gastrointestinal Endoscopy 2001;53:AB70.
Jacksonville Medicine / June/July, 2002

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