Nowadays, 5 nonsurgical flexible endoscopic techniques are available for small bowel endoscopy: push enteroscopy (PE), balloon-assisted enteroscopy using 2 balloons (double-balloon enteroscopy [DBE]) or 1 balloon (single-balloon enteroscopy [SBE]), balloon-guided enteroscopy (BGE), and spiral enteroscopy (SE). PE is a cost-saving, easy, and fast procedure for the examination of the proximal jejunum, but for a deep small bowel endoscopy, the other flexible enteroscopic techniques are required. BGE does not play a considerable role in deep small bowel endoscopy. DBE is the oldest flexible enteroscopic technique. Actually, the balloon-assisted enteroscopy (BAE) techniques with one balloon (SBE) or two balloons (DBE) are the mainly used techniques. DBE has become established throughout the world for diagnostic and therapeutic examinations of the small bowel and is now used universally in clinical routine work. DBE is still regarded as the gold standard nonsurgical procedure for deep small bowel endoscopy, because it provides the highest rates of complete enteroscopy, which becomes increasingly useful. The recently introduced SE technique represents a promising method but still needs technical improvement. Larger prospective studies on SE and prospective studies comparing the 3 systems (DBE, SBE, SE) are awaited before conclusive assessments can be made.
Flexible enteroscopy is a more invasive procedure in comparison with the purely diagnostic capsule endoscopy. However, the main advantages of flexible enteroscopy in comparison with other imaging procedures (eg, capsule endoscopy and magnetic resonance Sellink) are that it allows histologic sampling and endoscopic therapy. Nowadays, several techniques are available for the approach of the small bowel, including push enteroscopy (PE), balloon-assisted enteroscopy (BAE) using 2 balloons (double-balloon enteroscopy [DBE]) or 1 balloon (single-balloon enteroscopy [SBE]), balloon-guided enteroscopy (BGE), and spiral enteroscopy (SE). PE became established in the 1980s but is associated with only a limited depth of penetration into the small bowel. This limitation was overcome through the development of BAE using the DBE or SBE technique. In optimal cases, the entire small bowel, or at least considerable proportions of it, can be visualized using balloon enteroscopy (usually by combining the oral and anal examinations). This system has become established throughout the world for diagnostic and therapeutic small bowel examinations and is now being used universally in clinical routine work. In addition to the classic indication for small bowel endoscopy, the DBE or SBE technique has a variety of other potential uses as well, for example, in difficult ileocolonoscopies, for access to the pancreatic and biliary tract in patients with a surgically modified gastrointestinal tract, and for access to the stomach in patients who have undergone bariatric surgery. SE is another promising recently introduced enteroscopic system that is equipped with a raised helix at the tip of the overtube. In contrast to the BAE techniques, which follow the push-and-pull principle, this new enteroscopic technique pleats the small bowel by rotating.
Flexible enteroscopic techniques
Push video enteroscopes are 200- to 250-cm long devices (dependent on type and manufacturer) and might be used with a stiff overtube (85–120 cm) to prevent looping of the enteroscope in the stomach. Although initial studies showed an increase in the depth of insertion with the use of an overtube, later studies with graded-stiffness enteroscopes have questioned the additional value of the overtube. The following are the main advantages of PE: it is easy and quick to perform, it is not a staff-consuming procedure, the overtube is reusable, and there is no need to set up a special system (eg, a pump control system). All these facts avoid extra costs and, therefore, PE is a cost-saving technique for the investigation of the proximal small bowel. PE for the lower digestive tract is not commonly performed because insertion depth of colonoscopy with ileoscopy seems equivalent to lower PE.
The DBE system (Fujinon, Inc, Saitama, Japan) consists of a high-resolution video endoscope with a working length of 200 cm and a flexible overtube made of polyurethane. Latex balloons are attached both at the tip of the enteroscope and also on the overtube and they can be inflated with air or deflated using a pressure-controlled pump. At present, 3 different types of devices are available with the DBE system. First type is the EN450-P5 model with a working channel of 2.2 mm and an outer diameter of 8.5 mm. Second is the EN450-T5 model with a working channel of 2.8 mm and an outer diameter of 9.4 mm. The corresponding overtubes have diameters of 12.2 and 13.2 mm with an overall length of 145 cm. Third is the EC450-BI5 model with a length of 152 cm, an outer diameter of 9.4 mm, a working channel of 2.8 mm, and a corresponding overtube with a diameter of 13.2 mm and a length of 110 cm. This device is mainly used for difficult ileocolonoscopy, endoscopic retrograde cholangiopancreatography in surgically altered anatomy, or proximal small bowel endoscopy. The main advantage is that there is no need for specially designed accessories, and all standard equipment can be used.
The principle of the DBE technique is based on alternating pushing and pulling maneuvers and alternating inflation and deflation of the balloons, allowing the small bowel to be threaded step-by-step onto the overtube ( Fig. 1 ). Depending on the intention, the pleated small bowel can slip down very fast or slowly from the overtube during withdrawal, using the alternating inflation and deflation of the overtube balloon while pulling back the scope. To optimize the visualization, the balloon at the endoscope tip is used in addition to air insufflation, if necessary. The endoscope balloon can then be partly inflated to a balloon setting pressure of 4 to 5 kPa, helping to pull apart the pleated folds.