Performing Double-Balloon Enteroscopy: The Utility of the Erlangen EndoTrainer

Workshop Design 

Sixty national and international workshops, with a total of 632 participants, have been conducted in Wiesbaden between January 2004 and June 2006. The workshops were structured into 2 major parts, each of which was in turn subdivided into 3 parts. The workshops started with a lecture presenting general and technical data concerning DBE, as well as the results in comparison with other endoscopic modalities in the small bowel (eg, capsule endoscopy, push enteroscopy, and intraoperative enteroscopy). This was followed by a live examination of a patient with suspected or known small-bowel disease, after which training with hands-on enteroscopy using the Erlangen EndoTrainer was provided. After a break, further training with the EndoTrainer was possible if some of the course participants were interested in this. The course continued with a presentation and discussion of interesting case reports, a report on experience with DBE in Wiesbaden and in the published literature, and a special section with tips and tricks—particularly for therapeutic interventions with DBE—depending on the participants’ level of experience. After this, another live demonstration was performed. At the end of the workshop, there was a further opportunity to discuss important points and exchange experiences. Each participant receives a certificate at the end of the day.

Erlangen EndoTrainer 

The principle of DBE has been described in detail previously1, 2 and is illustrated in a simplified diagram in Figure 2. Although this enteroscopy technique appears to be quite simple, it is often hard to picture it in operation, especially at the beginning of the learning curve with the new technique. The development of an ex vivo model using animal intestines has been a very important step in teaching DBE in this respect.

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Figure 2. Diagram illustrating the principle of double-balloon endoscopy. Yellow, a deflated balloon; orange, an inflated balloon. (Color version of figure is available at www.techgiendoscopy.com.)

The model is based on the Erlangen EndoTrainer, which was developed in 1992 for teaching upper gastrointestinal endoscopy and endoscopic retrograde cholangiopancreatography (ERCP).6, 7, 8, 9 It consists of a human-shaped dummy and specially prepared porcine upper visceral organ packages. The organ package is attached to the dummy using several sutures that are made immediately before the model is prepared for the training course. For the special conditions needed in DBE, the model was modified, and the whole duodenum and 150-200 cm of small bowel were prepared.9 The dummy’s anatomy is completed with a head produced with synthetic material that allows realistic insertion of the enteroscope into the mouth and passage through the esophagus and stomach. For training in DBE, a transparent ventral shell or open dummy was chosen to allow visual orientation and visualization of the way in which the small bowel is threaded onto the overtube during the push-and-pull procedures (Fig. 3).

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Figure 3. In vitro animal model using a modified Erlangen EndoTrainer.

This model is highly suitable for illustrating the principle of DBE, including the associated stresses to which the small bowel is exposed due to the shearing and traction forces exerted during the individual push-and-pull maneuvers. It allows the anatomic features of the small bowel to be studied, and important points that need to be taken into account during DBE can be displayed in a very graphic way, eg, the optimal positioning of the device in the small bowel and the effect that air insufflation during enteroscopy and the trapping of air between the small-bowel folds has on the process of threading the small bowel onto the overtube. The model also allows hands-on training, in which users can practice the sequences of individual steps. Training in therapeutic interventions can of course also be provided with the model. The major disadvantage and limitation of this model is that it can be only used for training in the oral DBE procedure. The experience of the Murcia group has been that the best way of providing training with the anal route is to use a live dog model (personal communication, Enrique Pérez-Cuadrado, Murcia, Spain, at the 2nd International DBE Meeting, Berlin, Germany, June 16th, 2007).

Outcomes 

Speed and Depth of Insertion 

One of the most important points for fast and especially deep insertion is air insufflation during the DBE procedure. The larger the amount of air that is insufflated during insertion of the endoscope and pulling back of the endoscope and the overtube, and the smaller the amount of air that is sucked out between the individual steps of the push-and-pull maneuvers, the greater the space that is needed on the overtube for threading the small bowel (Fig. 4). Due to this air trapping, the overtube quickly becomes “full” of small bowel; no more small bowel can be threaded onto the overtube, and the DBE procedure has to be stopped, independently of the depth of insertion achieved up to that point. This can be illustrated very clearly with the EndoTrainer model.

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Figure 4. Air trapping in the small bowel. (Color version of figure is available at www.techgiendoscopy.com.)

To reduce the amount of air insufflation needed when the small bowel is empty of air and liquid and “stuck together” in a patient, an injection of water combined with simethicone, for example (to reduce bubble formation) can be recommended, as the small bowel opens up quickly after fluid injection. The use of CO2 instead of air might also solve this problem in the future.

The next point that has to be considered is the straightening of the scope and resolving of loops formed during insertion of the scope and during pulling back of the scope and the overtube. The fewer the loops that have formed, the deeper the enteroscopy that can be expected, and complete enteroscopy may even be possible. This is easily demonstrated thanks to the transparent ventral shell in the open dummy. When patients are being examined, the use of fluoroscopic monitoring during the straightening process is helpful, especially at the start of the learning curve and in difficult situations, such as those caused by adhesions due to prior abdominal surgery. Figure 5 shows fluoroscopic images of the optimal positions of the scope for the oral and anal approaches and of a complete enteroscopy with oral DBE.

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Figure 5. (A) Fluoroscopic image of an optimal position for the oral route. (B) Fluoroscopic image of an optimal position for the anal route. (C) Fluoroscopic image of complete enteroscopy using oral double-balloon endoscopy.

Choosing the prone position for oral DBE leads to a certain amount of compression of the patient’s abdomen, which can be helpful during advancement, at least in patients with a normal or increased body mass index. In thin patients, the additional use of a rigid pillow may be helpful.

In my own experience and opinion, the P-type scope (Fujinon EN-450P5/20) is more useful for deep insertion or even complete enteroscopy during oral DBE, as the instrument is more flexible and robust than the thicker T-type (Fujinon EN-450T5).

Insertion of Accessories 

When the enteroscope is positioned deep in the small bowel, it can sometimes be difficult to insert accessories, eg, thin argon plasma coagulation probes or injection needles. Application of approximately 2 mL of silicone oil into the working channel just before using the accessories facilitates their advancement. In the case of injection needles, it is very important to use needles with a stiff catheter and a sharp tip on the needle. In addition, the endoscopist has to take care that the tip of the enteroscope is not flexed too much and that there are no small loops (Fig. 6). During teaching with the EndoTrainer, these factors can easily be demonstrated with the “open” small bowel. In the case of a DBE procedure in a patient, fluoroscopic monitoring is helpful for visualizing the problem and changing the position of the enteroscope.

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Figure 6. The flexed tip of the enteroscope and a small loop of the enteroscope.

Teaching Therapeutic Interventions with the EndoTrainer 

All of the therapeutic endoscopic interventions that are familiar in conventional endoscopy can also be performed in the deep small bowel using DBE. However, there are a few factors that make these interventions more difficult. First, there is a long scope with a thin working channel and consequently long, thin probes, making very careful handling necessary. Despite the balloons, which help stabilize the position of the scope, it is sometimes tricky to obtain a good, stable position for difficult procedures, eg, for resecting large polyps. In addition, the lumen is narrower in the small bowel than in the stomach or colon, for example, and the small-bowel wall is very thin, comparable to the right-sided colon. The latter point in particular can be demonstrated very impressively using argon plasma coagulation with different energy levels or marking a position with india ink, for example.

Summary 

DBE is a complex examination and should therefore only be performed by experienced endoscopists. The best method of teaching DBE is step-by-step training. Lectures and videos are very useful during the initial steps, whereas hands-on training with animal models and demonstration of live DBE procedures are the main components used for providing training in and teaching of DBE. Ex vivo pig models, such as the modified Erlangen EndoTrainer, are preferable.