The small bowel is the most difficult segment of the gastrointestinal tract to investigate. The present review describes the evolution of enteroscopy, from the first complete enteroscopy in 1971 through the current balloon-assisted and overtube-guided methods to likely future development directions aiming for enteroscopic perfection.
by Dr Tom G. Moreels
The wireless videocapsule was released in 2000 and has opened the last ‘black box’ of the gastrointestinal tract, enabling complete endoscopic visualisation of the small bowel [1]. Since then numerous new developments from various companies have emerged, with improvements in image quality, number of images recorded per second and length of battery life. In addition the software to read the images is becoming ever faster and smarter, and newer developments focus upon the design of an “interventional” capsule enabling tissue sampling, directed medication delivery and functional evaluation of the small bowel.
Parallel to the development of the diagnostic wireless videocapsule, conventional enteroscopy was also subjected to a new evolution in order to perform all conventional endoscopic interventions throughout the small bowel. An overview of the endoscopic developments to explore the small bowel is given below.
Yesterday’s enteroscopy
Already in the 1970s complete enteroscopy using a conventional fibre endoscope was shown to be possible [2]. By means of the ropeway method, a long fibre endoscope was pulled down the gastrointestinal tract after a rope loaded with a weight travelled from mouth to anus along with gastrointestinal peristalsis.
The sonde type method involved a long thin fiberscope with an inflatable balloon at its distal tip. The scope was inserted through the nose into the stomach from where it was further progressed beyond the pylorus using a conventional endoscope. Then the balloon at the tip of the fiberscope was inflated to serve as a bolus that was acted on by intestinal peristalsis to carry the fiberscope down the small intestine [3]. Although both the ropeway and sonde type method were effective to visualise the entire small bowel, and gave the possibility of tissue sampling, the procedures were very inconvenient and could last several days.
In the 1980s intraoperative enteroscopy became available as a feasible alternative that is still used today, although it requires a surgical approach through laparotomy. It can be performed via the oral route or the anal route but often enterotomy is necessary [4]. Because of its invasiveness the technique is generally reserved as a last-choice approach.
At the same time push enteroscopy was developed during the 1990s and rightfully replaced the previous inconvenient and invasive enteroscopy methods [5]. Longer conventional endoscopes were developed to proceed beyond Treitz’s angulus. Push enteroscopy allows endoscopic evaluation of the proximal jejunum through the oral route. Because of the flexibility of the enteroscope and the tortuous length of the small bowel, complete enteroscopy is not possible. The pushing force used to progress the enteroscope throughout the small bowel results in stretching of the jejunum, thus hampering further progress and causing patient discomfort.
The introduction of a semi-rigid overtube allows deeper intubation of the jejunum because it helps to straighten the enteroscope and avoids jejunal stretching [6]. The use of an overtube was an important development, leading to a major improvement in insertion depth and an increase in the yield of push enteroscopy. However, overtube-guided push enteroscopy only allows intubation of the jejunum without complete enteroscopy [7].
Today’s enteroscopy
Although both intraoperative enteroscopy and overtube-guided push enteroscopy are still in use, new developments have emerged which have given rise to improved enteroscopy performance. The concept of balloon-assisted enteroscopy is a second major breakthrough in the evolution of the endoscopic disclosure of the small bowel. In 2001 the Japanese endoscopist Hirohito Yamamoto revolutionised the concept of overtube-guided enteroscopy by adding an inflatable latex balloon at the distal end of the flexible overtube, allowing better mucosal grip of the overtube, stabilising its position within the intestinal lumen. In addition, a second inflatable latex balloon was added to the distal end of the enteroscope. With this self-made double-balloon model, he was able to intubate the entire small bowel through the oral route [8]. Since 2003 the double-balloon enteroscope has been commercially available from Fujinon [Figure 1].
Following the success of double-balloon enteroscopy, the Olympus company developed another system of balloon-assisted enteroscopy that became commercially available in 2007, namely single-balloon enteroscopy that is largely comparable to double-balloon enteroscopy. It consists of a latex-free balloon-loaded overtube lacking the balloon at the distal end of the endoscope [Figure 2].
Both balloon-assisted methods are based upon the push-and-pull principle [9]. It is a stepwise progression of the enteroscope through the small intestine with the balloon-loaded overtube used as a straightening device, allowing stable position within the intestinal lumen. The extra balloon at the distal end of the endoscope in the double-balloon system allows better anchoring of the endoscope within the lumen, whereas the single-balloon system allows faster progression of the endoscope throughout the small bowel. Both balloon-assisted methods allow complete intubation of the small bowel within a reasonable procedure time, although often a combined approach through the mouth and the anus is necessary to complete enteroscopy. In addition, all conventional endoscopic interventions, ranging from mucosal tissue sampling, local hemostasis, polypectomy and balloon dilation, can now be performed throughout the length of the small bowel thanks to balloon-assisted enterosopy. Moreover, excluded gastrointestinal segments after previous small bowel surgery have come within endoscopic reach, allowing ERCP procedures in patients with Roux-en-Y reconstruction of the small bowel [10]. These important advantages have led to a rapid spread of both balloon-assisted enteroscopy systems in endoscopy suites throughout the world.
A novel alternative balloon-assisted method is the NaviAid balloon-guided enteroscopy, developed by Smart Medical Systems and distributed in Europe by Pentax. It consists of a standard enteroscope loaded with a stabilising latex-free inflatable balloon at the distal end of the endoscope and an advancing balloon-catheter mounted on the outer perimeter of the endoscope. The principle is comparable to double-balloon enteroscopy, without an overtube. Preliminary results reveal that this technique allows deep intubation of the small bowel, but complete enteroscopy has not been achieved [11]. The results of multicenter trials are awaited in order to determine the true clinical value of this new device.
Next to balloon-assisted enteroscopy, Spirus Medical adapted the overtube resulting in the development of the EndoEase discovery small bowel overtube. This spiral overtube enteroscopy allows rapid and deep intubation of the small bowel through the oral route [12]. The endoscope remains in a stable position and by rotating the overtube with its raised helices, the small bowel is pulled backwards over the endoscope. It seems to be a feasible, rapid method, however mucosal and transmural traction lesions have been reported. Comparative studies between balloon-assisted enteroscopy and spiral overtube-guided enteroscopy are awaited.
Tomorrow’s enteroscopy
Both wireless video capsule enteroscopy on the one hand and balloon-assisted and overtube-guided enteroscopy on the other are undergoing significant development processes, since no single method is ideal. Although wireless video capsule enteroscopy allows complete visualisation of the small bowel without discomfort, it remains a merely diagnostic procedure with significant level of false negative results. On the other hand, balloon-assisted and overtube-guided enteroscopy are invasive and time-consuming techniques with a lower chance of complete enteroscopy, allowing all conventional endoscopic interventions within the small bowel.
The aims of each of the current development activities are a higher yield, reduced patient discomfort, no complications and better interventional options, which would represent the ideal, perfect objective. However, it is unlikely that both approaches will ever come together in one final, perfect endoscopic tool for the investigation and treatment of small bowel pathology. It looks as though, over the next few years at least, wireless video capsule enteroscopy and balloon-assisted and overtube-guided enteroscopy will remain the “yin and yang” of small bowel visualisation, perfectly complementing each other’s imperfections.
References
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The author
Tom G. Moreels
Antwerp University Hospital
Department of Gastroenterology & Hepatology
Wilrijkstraat 10
B-2650 Antwerp, Belgium
Tel. +32-3-821 4974
E-mail: tom.moreels@uza.be
