Editorial

 

Capsule endoscopy: a new era in the history of endoscopy

 

When the first experiences with capsule endoscopy (CE) in 10 volunteers were reported in May 2000 (1), many of us understood that a new era in the history of gastrointestinal endoscopy was dawning, and that the so-long-awaited and peculiar “fantastic voyage” had at last come true. The wireless capsule (WC) model that was eventually made available by the Israeli company Given Imaging under the M2A denomination, a combination of the device that physicist G. Iddan had developed for almost two decades, and that devised by Dr. P. Swain (1), was first at the finish line among all those who started the race in an attempt to reproduce the movie fiction that R. Fleischer had filmed back in 1966, based on a brilliant story by I. Asimov. Some editorials on this development mentioned this classic science-fiction piece (2), even though I must say in all modesty that I had already intuitively felt and premonitorily anticipated this invention several years before (3). Approved for clinical use by the FDA in 2001, this same Northamerican organization accoladed CE when on July 2, 2003 they declared it to be “the first-choice diagnostic method for small bowel conditions”. The FDA concluded so upon their analysis of data from 32 reported clinical studies including 691 patients, and a comparison of their results with those obtained from other small bowel examination modalities such as upper endoscopy, ileocolonoscopy, push enteroscopy, intraoperative enteroscopy, gastrointestinal follow-through, abdomen scanning, and angiography.

As is usual with new technologies, CE still has a wide group of skeptics and detractors amongst endoscopists themselves; despite this, however, it is becoming progressively established as the best diagnostic method available for small bowel conditions (2,4). Diagnoses at this level did not share the quality, sensitivity and specificity of those for other sites within the gastrointestinal tract, and remained often incomplete, until CE became available. Oral panendoscopes may reach as far down as the lower duodenal genu, whereas push enteroscopy may usually not go beyond mid jejunum. Similarly, an examination of the terminal ileum using a colonoscope is not always feasible, or is commonly limited to 20-25 cm when it is. Therefore, from an endoscopic viewpoint, too many blind spots existed within the small bowel that rendered studies unsatisfactory. CE-based diagnoses of small bowel lesions have always been superior to those provided by other more or less conventional techniques such as radiography (5), push enteroscopy (6), and CT follow-ing intestinal enteroclysis (7) in comparative, prospective trials. Obviously, CE still has a long way to go regarding its ability to display images in real time, to accurately identify the site where images are acquired, to be directed from outside the body, and last but not least to collect samples for histology or deliver some sort of therapy. Of course, reality will surpass the fantastic voyage fiction when all this becomes eventually possible, as it will.

Although CE transmits images from the esophagus, stomach and colon, it currently cannot be considered a method for the exploration of such organs (2, 4), since traditional endoscopy is a more thorough, accurate and useful technique at these sites. The same happens with the duodenum, although the diagnostic accuracy of CE is certainly comparable at its distal portion.

The primary indication of CE is the study of gastrointestinal bleeding of obscure origin (GIBOO) both in patients with obvious recurring hemorrhage and patients with occult blood loss detected by occult blood in feces testing. When a diagnosis is not reached after conventional examination in patients with GIBOO, CE may diagnose lesions accounting for blood loss in around two thirds of cases, and vascular injury, erosion, and ulcer are the most common findings (8-10). Thus far, the diagnosis of GIBOO relied on push enteroscopy (11) or intraoperative enteroscopy (12), methods that achieve a diagnosis in one third of patients. When the efficacy of CE is compared to that of push enteroscopy in these patients with GIBOO, CE is clearly superior (10).

Another currently accepted indication of CE is the study of abdominal pain in association with chronic diarrhea when Crohn’s disease is suspected but no evidence is provided by conventional examinations (13-15). Indeed, in the absence of a histological study a risk is run that these patients are overdiagnosed, and that patients with lesions from other etilogies, such as continued or incidental NSAID ingestion or –why not?– a still overlooked food allergy, receive a Crohn’s disease diagnostic label. CE is proving now its usefulness in the identification of iatrogenic bowel injury both in patients receiving NSAIDs or anovulatory drugs, and in those undergoing radiaton therapy or abdominal surgery; in NSAID ingestion cases, a number of bowel lesions far greater than previously expected has been found, both for classic and anti-COX2 anti-inflammatory drugs (16). Similarly, the study of selected malabsorption patients is considered an indication for CE, particularly when an expected course occurs or the presence of a tumor such as primary intestinal lymphoma is suspected. It is also indicated for extension studies in patients with intestinal polyposis –as is the case of a Peutz-Jeghers syndrome– where CE may be used as an exploratory step prior to therapeitic decision making. Lastly, CE may be indicated for suspected bowel tumors.

It is in this setting –where CE is shown to be the best diagnostic method for small bowel conditions– that the contribution by A. Caunedo and colleagues to this issue of Revista Española de Enfermedades Digestivas (17) should be evaluated in. The authors –Caunedo et al.– who belong in the group that pioneered CE in our country (18,19), perform a retrospective analysis of CE studies in 88 patients seen over twelve months, and in whom CE was indicated because of the following reasons, by order of frequency: chronic diarrhea in 33 patients, unexplained abdominal pain in 29 patients, GIBOO in 13 patients, NSAID ingestion in 7 patients, gastrointestinal tumor extension study in 4 patients, and 2 controls. This is a copy of the aforementioned accepted indications. Since indications vary so much in this group, the most relevant conclusions of this work may be the high frequency of CE-demonstrated lesions (examinations revealed no changes in only 11 patients), and that most commonly found lesions include erosion and vascular malformations, that is, results similar to those reported by many of the published studies. The authors diagnosed 29 patients with Crohn’s disease, which represents 33% of studied cases. I for one consider this figure to be rather high regarding this diagnosis, particularly in the absence of histologic studies; however, as complete information on the clinical and outcome aspects of these patients was not made available to me, I recognise my in-ability to make value judgments on said findings, and time as judge supreme will put things in their place. The number of intestinal tumors diagnosed in 6 patients is also of note, and represents the increasingly obvious fact that the small bowel may suffer from a wide and varied number of neoplastic conditions.

A few words now on CE contraindications and complications. Absolute contraindications include intestinal pseudo-obstruction and obstruction, and relative contraindications include dysphagia, achalasia, gastroparesis, Zenker’s diverticulum, and resective and/or derivative gastric surgery (20). In case of a relative contraindication and when in urgent need for CE, special techniques for the capsule’s introduction into the small bowel may be used with the help of an oral panendoscope. Patients who fail to expel the capsule must not undergo magnetic resonance imaging. The presence of a pacemaker is not currently considered a contraindication.

Complications are rare, and capsule retention due to achalasia, stenosis, Zenker’s diverticulum, colonic diverticula, or the passage of the capsule into the airway stands out amongst them. Retention at a point with stenosis is the most common and significant complication, and may require a surgical procedure to solve it, as was the case with a female patient in the series by Caunedo et al. capsule retention occurred in 22 out of 1711 patients included in all reports on CE at the DDW 2003, held in Orlando, which represents 1.28% of patients, with 18, that is, 1.05% of studied cases requiring surgery to solve it (21). To prevent this complication from occurring, Given Imaging has developed the so-called “capsule patency” method, consisting of a mock capsule that is similar in both shape and size to the actual WC, and which melts away should retention develop; its expulsion unscathed is indicative that an actual WC may travel safely through the gut. This mock capsule is currently in trial.

In summary, we are now in a new era of gastrointestinal endoscopy, in which we must learn how to assess new situations, how to identify and classify images that were previously unknown, and how to modify therapy approaches for some patients. This is not the time for either celebrations, or skepticism, or groundless criticism. Virtue always lies where balance and moderation abound, and so it is for the fantastic voyage of gastrointestinal endoscopy.

J. L. Vázquez-Iglesias

Servicio de Aparato Digestivo. Complejo Hospitalario Universitario Juan
Canalejo. La Coruña

 

REFERENCES

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