Total enteroscopy can be achieved using SBE. Usually, total small bowel visualization is confirmed by inserting the enteroscope through both the oral and anal routes and marking the midway point with an Indian ink tattoo or endoscopic clipping (Figures 1 and 2). The initial experience reports of SBE in Japan have been characterized by total enteroscopy rates of 12.5% to 71.4% (Table 1)[2-5].

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Figure 1 Case of total enteroscopy. A: Single-balloon enteroscope inserted orally; B: Indian ink was used as a tattoo in the deepest part of the intestine.

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Figure 2 Case of total enteroscopy (continued). A: Single-balloon enteroscope inserted anally; B: Tattoo marked when enteroscope was inserted orally was confirmed.

Three randomized, controlled trials thus far have compared the rates of total small bowel visualization by DBE and SBE[10-12]. May et al[10] reported that complete enteroscopy was achieved with the DBE technique in 66% (33/50) of cases and only 22% (11/50) with the SBE technique (P < 0.0001). However, this study had a number of significant limitations. One was that the SBE system used in this study was not the original system produced by Olympus, but a DBE system made by Fujifilm Corporation (Tokyo, Japan) without the tip balloon attached. In 2011, Takano et al[12] also reported worse results for the insertability of the SBE system developed by Olympus compared to those for the DBE system developed by Fujifilm. The total enteroscopy rate was 0% in the SBE group and 57.1% in the DBE group (P = 0.002). This result suggested that the insertability of SBE might be inferior to that of DBE. However, Domagk et al[11] reported that DBE and SBE have comparable performance in the evaluation of the small bowel. Their study revealed that complete visualization of the small bowel was achieved in 18% and 11% of procedures in the DBE and SBE groups, respectively. These randomized control studies yielded conflicting results concerning the insertability of SBE compared to that of DBE.

We have discussed the insertability of SBE using total enteroscopy rate as a comparative parameter, because none of the currently known methods of estimating insertion depth are ideal[13]. However, the clinical impact of total enteroscopy rate is controversial, because in majority of the patients the fact whether total enteroscopy is achieved is not necessary to diagnose small bowel diseases[14]. Lenz et al[8] indicated that the first-choice enteroscope should be selected according to availability, physicians’ experience, and clinical implications.

In the next section, the many methods of improving the insertability of SBE will be discussed.

The most important difference between SBE and DBE is the manner in which the small intestine is held by the tip of the enteroscope during sliding tube insertion. If the holding force is not sufficient, the enteroscope will slip back. Ohtsuka et al[15] discussed the method of improving the holding force in the small intestine using the SBE technique. To prevent the scope from slipping back during sliding tube insertion, it is important to use both upward and left angulation, as this helps to increase the holding force applied by the tip of the enteroscope. Furthermore, they recommended the use of a distal attachment to assist the fixation of folds in the small intestine.

A recent study suggested the usefulness of carbon dioxide insufflation during the SBE procedure in improving intubation depth[16,17]. Li et al[17] reported that the total enteroscopy rate of the carbon dioxide insufflation group was significantly higher than that of the air insufflation group (34.9% vs 17.6%; P = 0.006). Lenz et al[16] reported that oral intubation depth was significantly higher in the carbon dioxide group than in the air group (258 ± 84 cm vs 192 ± 42 cm; P < 0.05) in patients with previous abdominal surgery.

By using the techniques described above alongside carbon dioxide insufflation, the depth of SBE insertion devices can be improved. Interestingly, Ohtsuka et al[15] reported several cases of total enteroscopy using only the anal approach.

SBE is a safe diagnostic endoscopic procedure. However, serious complications such as acute pancreatitis[18,19] and perforation[20] could occur, although the rates of these complications are very low. Aktas et al[21] reported that while post-SBE hyperamylasemia occurred in 16% (13/81) patients, no acute pancreatitis was observed in 105 consecutive patients undergoing peroral approach SBE. Lenz et al[22] reported that the rate of severe adverse events after SBE procedures was only 0.6% (2/298) and did not differ significantly from that after DBE procedures in their large case series.

Parikh et al[23] summarized the clinical applications of SBE for small bowel diseases in 615 patients reported thus far in their review article. The most common indication of SBE was obscure gastrointestinal bleeding (51%), followed by evaluation for Crohn disease (13%) and polyp/mass (8%). The most common lesions of the small bowel were angioectasias (22%), ulcers (15%), and polyp/mass (10%), and the most common interventions included hemostasis with argon plasma coagulation (22%), followed by polypectomy (3%) and dilation (3%).

Although there were conflicting results regarding the insertability of SBE compared with that of DBE, the diagnostic yield of small intestinal lesions using SBE was reported as equal to that of DBE. Diagnostic yields were 41%-65% in initial experience reports[2,5,24] and 37%-50% in randomized control studies[10-12], which were almost same as the rates of the DBE system.

Recently, SBE for disease in regions other than the small bowel has been reported. In the next session, the clinical applications of SBE for colonic and pancreatobiliary lesions are discussed.

There are two main reasons for performing SBE for colonic lesions: One is when colonoscopy fails, and another is when endoscopic submucosal dissection (ESD) is required in difficult positions.

An elongated colon and adhesion would make it difficult to achieve total colonoscopy. SBE is used to prevent stretching of the intestine. A case series suggested that the SBE system is successful in almost all patients in whom the cecum cannot be reached[25-27]. A randomized control trial revealed that the utility of SBE and DBE for colonoscopy seemed comparable in patients with incomplete previous colonoscopy using a conventional colonoscope[28].

ESD for colonic neoplasm is a technically challenging procedure, especially if the target neoplasm resides in a difficult to reach position. An overtube with a balloon is used to stabilize the endoscope during the ESD procedure. Ohya et al[29] reported the usefulness of a therapeutic gastroscope (GIF-Q260J; Olympus Medical systems, Tokyo) with an SBE overtube for colonic ESD. The SBE overtube was too long to use with the gastroscope, so a modified and shortened overtube of 70 cm from the distal end was used.

SBE is useful for both small bowel diseases and pancreatobiliary diseases in patients with altered gastrointestinal anatomy. Many studies have reported the usefulness of the SBE system for endoscopic retrograde cholangiopancreatography (ERCP) with altered gastrointestinal anatomy, especially in patients with Roux-en-Y anastomosis[30-43]. However, a limited number of ERCP accessories are compatible with the SBE system because of its narrow inner channel diameter and working length compared to those of a conventional duodenoscope. Recently, the usefulness of the short-type SBE prototype (SIF-Y0004; Olympus medical systems, Tokyo) has been reported[44-49]. The short-type SBE has a working length of 1520 mm and an inner channel diameter of 3.2 mm (Figure 3), which are both compatible with many conventional ERCP accessories (Figure 4). In the future, this short-type SBE system may become the first-choice endoscope for ERCP in patients with altered gastrointestinal anatomy.

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Figure 3 Short-type prototype single-balloon enteroscope. This scope has a working length of 1520 mm and an inner channel of 3.2 mm, which are compatible with those of many endoscopic accessories. SBE: Single-balloon enteroscopy.

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Figure 4 Case of common bile duct stones treated using a short-type prototype single-balloon enteroscope. Conventional endoscopic accessories such as retrieval balloon catheter (A), endoscopic sphincterotomy catheter (B), and endoscopic balloon dilation catheter (C), were used in this procedure.

Recently, the efficacy and safety of SBE for children with Crohn disease and Peutz-Jeghers syndrome have been reported[50-52]. SBE is expected to be as useful in children as in adult patients.

Endoscopic removal of foreign objects, diagnosis of parasite infestation, and SBE-assisted direct percutaneous endoscopic jejunostomy are reported as uncommon uses of SBE[53-56]. In cases in which the target regions lies in the small bowel, not far from the ligament of Treitz or the terminal ileum, the balloon at the tip of the enteroscope may not be needed. SBE might have advantages compared to DBE in such cases because of SBE involves a greater ease of preparation.