Deep enteroscopy has both diagnostic and therapeutic applications. The most common indication for deep enteroscopy is evaluation of obscure gastrointestinal (GI) bleeding [28]. Other indications include evaluation of imaging abnormalities, anemia, small bowel Crohn’s disease, strictures, ulcers, polyps, masses, foreign bodies, lymphoma, other infiltrative diseases, and jejunal feeding tube placement (Table 13.1). While any procedure performed with a gastroscope or colonoscope can be accomplished with an enteroscope, due to looping and difficulty in advancing tools out of the biopsy channel, it may be challenging to perform more complex therapeutics such as endoscopic mucosal resection and endoscopic submucosal dissection.

DBE is a novel enteroscopy technique first reported in Japan by Hironori Yamamoto in 2001 [24], and commercially developed by Fujinon Corporation (Tokyo, Japan). This is also known as ‘push-and-pull enteroscopy’ [55], which uses a novel method whereby an endoscope and a soft flexible overtube, each of which has an inflatable balloon attached to its distal end, are employed together and an external pump system aids in inflating the balloons; both balloons can be inflated and deflated separately [56]. There is a standard 200-cm-long DBE scope (Fujinon EN-450P5) with 8.5 mm outer diameter and 2.2 mm channel size (Fig. 13.2) and also a couple of therapeutic DBE scopes (Fujinon EN-450T5 and Fujinon EN-450T5/W), which accommodate both endoscopic retrograde cholangiopancreatography (ERCP) and colonoscopy accessories with 2.8 and 3.2 mm working channels. The slim Fujinon EN-450P5 aids smooth antegrade insertion enabling visualization for diagnostic purposes, whereas the Fujinon EN-450T5 and Fujinon EN-450T5/W scopes allow the use of almost all therapeutic accessories including the argon plasma coagulation (APC) probe, hemoclip, and diathermic coagulator. A shorter 152-cm-long therapeutic DBE scope with 2.8 mm working channel (Fujinon EC-450BI5) is primarily used for cases of incomplete colonoscopy and for ERCP in patients with surgically altered anatomy (Table 13.2).

Once the DBE with the overtube is inserted in the usual fashion into the small bowel, the endoscope is advanced through the overtube with the inflated balloon on the overtube acting as an anchor maintaining a stable position (Fig. 13.3). Once the enteroscope has been advanced as far as possible, the enteroscope balloon is inflated, the overtube balloon deflated, and the overtube advanced along the enteroscope. Then the overtube balloon is inflated followed by reduction of loops by pulling back on both the overtube and the enteroscope. The enteroscope balloon is deflated to allow further advancement of the enteroscope. The process is repeated until the entire small bowel is visualized or the farthest extent is reached at which point tattoo should be applied (see Video 13.1). Either the enteroscope balloon or the overtube balloon or both are kept inflated at all times to maintain anchorage in the small intestine, enabling the steady insertion of the enteroscope (Fig. 13.3). DBE is used in the retrograde approach as well as with intubation of the ileum. The depth of insertion is greater with the antegrade than with the retrograde approach (360 ± 178 cm versus 182 ± 165 cm from the pylorus, p < 0.0001) [58].

DBE is superior to PE with a higher success rate for deep small bowel intubation and an increased diagnostic yield [59]. The diagnostic yield using DBE is between 40 and 80% leading to a subsequent change in management in 57–84% of patients [58–61]. On a review from 66 studies, Xin et al. noted an overall rate of positive findings of 68% with the highest diagnostic yield (86%) occurring for the indication of small bowel obstruction. Inflammatory lesions were most commonly identified in overall 33% of cases followed by vascular lesions in 29% and neoplasms in 23% [62]. For the indication of small bowel GI bleeding, vascular lesions were most frequent in 40% followed by inflammatory lesions in 30% and neoplastic lesions in 22%.

Although the detection rate for obscure GI bleeding with VCE is superior to DBE, these procedures are complementary. An initial diagnostic imaging employing VCE might be followed by therapeutic and interventional DBE [63]. The time index, defined as lesion location as a percentage of the mouth–cecum time [64], from VCE helps in choosing the best insertion route (antegrade vs. retrograde) for DBE [65], and also VCE-directed DBE increases the diagnostic yield in obscure GI bleeding [66]. It has been suggested that the retrograde DBE approach should be the initial approach when the lesion is at a location greater than 75% of the timeline of the capsule study (i.e., time index >0.75) [64].

The success rate of total enteroscopy ranges widely from 20 to 44% with 98% of the successful cases requiring both an antegrade and a retrograde approach [62, 67] Given such low-to-average success rates of total enteroscopy with DBE, endoscopists should remember to set expectations not only to patients, but also to themselves to avoid disappointment and to avoid unduly prolonging the procedure.

The complication rates with DBE range from 2 to 9% [62, 67] and apart from the usual expected complications, which include perforation, bleeding, and aspiration pneumonia, pancreatitis is seen in some cases (0.5%) [68, 69]. The cause for pancreatitis in DBE (when ERCP is not performed) is thought to be prolonged inflation of the balloon near the ampulla. Of note, perforation is significantly higher (3%) in patients with post-surgical anatomy, especially with the retrograde approach (10%) [68].

As with any other endoscopic procedure, DBE should not be performed whenever a small bowel perforation or high-grade intestinal obstruction is suspected or the risks of the procedure outweigh the potential benefits. DBE involves forceful distention and traction, and therefore, conditions with pre-existing weakened intestinal wall, such as recently created intestinal anastomosis, severely ulcerated small intestine, and small bowel lymphoma undergoing active chemotherapy is susceptible to perforation with DBE [70].

As with other procedures, technical skill in performing DBE improves with experience. While some studies show no learning curve for antegrade DBE [71], others demonstrate a significant decline in overall procedural time and fluoroscopy time after the initial 10 DBE cases [58]. The average time taken for adequate insertion is long and reported as 102 ± 38 min [58]. The improvement in procedure duration was observed only for anterograde cases, and not with retrograde examinations. About 30 retrograde cases are required for stable overtube intubation into the ileum [71]. More than 150 DBE procedures are necessary for increased rate of total enteroscopy and helpful DBEs that provide definitive explanation of symptoms or imaging abnormality, therapy, or guide management [72].

The SBE system was first introduced in 2007 by Olympus Corporation [25, 56]. SBE uses an enteroscope with a 2.8 mm working channel and an overtube which is equipped with a silicone balloon at its tip that can be inflated and deflated (Fig. 13.4) [25]. There is no balloon attached to the enteroscope. The basic insertion technique is similar for both SBE and DBE. However, in SBE the scope tip is deflected to anchor onto the small intestine, rather than using a second balloon. The overtube is advanced to the distal portion of the scope at which point the overtube balloon is inflated. The enteroscope tip is subsequently returned to luminal view and advanced as far as possible. At this point, the enteroscope scope is deflected for anchoring, the overtube balloon is deflated, and the overtube advanced over the enteroscope. The overtube balloon is inflated, the tip of the enteroscope is straightened, and both the overtube and enteroscope are reduced. This pleats the small intestine onto the overtube, and the enteroscope can be advanced again. This sequential technique of advancement and withdrawal is repeated until the scope can no longer be advanced or the target lesion is reached (Fig. 13.5) (see Video 13.1). When compared to DBE, SBE is technically easier to perform and appears to provide similar diagnostic and therapeutic yield [73, 74]. With SBE, a mean distance of 203.8 ± 87.6 cm from the pylorus with the antegrade approach and 72.1 ± 41.1 cm from the ICV with the retrograde approach can be achieved [74]. Both SBE and DBE are useful in performing ERCP in patients with surgically altered anatomy [40, 75, 76].

Spiral enteroscopy, which was originally designed as a urinary catheter in 2006, is a newer technique for deep small bowel intubation that uses a special single-use overtube [Discovery Small Bowel (DSB)] with soft spiral coils to pleat small bowel and facilitate antegrade small bowel enteroscopy. The DSB is 118 cm long with 16 mm outer diameter and 9.8 mm inner diameter, which accommodates an enteroscope or pediatric colonoscope [78]. The proximal end of the overtube has two handles for rotation, a locking device, and a port for lubrication. Using the DSB overtube over enteroscopes was first reported in 2008, [26] and DSB was also FDA approved in 2008 as an overtube (Endo-Ease Discovery SB, Spirus Medical, Stoughton, MA) that facilitates endoluminal advancement through the small intestine (Fig. 13.6). The overtube is lubricated and locked onto the enteroscope with the distal end of the overtube ending 25 cm proximal to the tip of the scope. If general anesthesia is used, the endotracheal balloon should be deflated as the DSB is advanced into the esophagus. Once the enteroscope is distal to the ligament of Treitz, the overtube is unlocked and the scope advanced forward. The overtube is then advanced to the tip of the scope, locked in place, and clockwise rotation of the Discovery SB is performed, similar to the mechanism used with a corkscrew. This pleats the small bowel onto the overtube. Then the overtube is unlocked, the enteroscope advanced forward, and the handles rotated counterclockwise to release the mucosa from the overtube. The Discovery SB overtube should be fixed to the enteroscope for spiral advancement or unlocked when conventional manipulation of the endoscope is needed.

The maximum depth of insertion beyond the ligament of Treitz (approximately 250 cm) for SE is comparable with DBE and SBE [79–81]. While the procedure time of about 60 min does not significantly differ between SBE and DBE, the mean procedure time is significantly less with SE (41 min) than with DBE or SBE [74, 82]. Recent prospective studies concluded that the only advantage of SE is that it involves significantly shorter examination times, but that SE was no better than DBE with regard to the depth of insertion or the rate of complete enteroscopies achieved [81, 83]. Complication rates with SE are similar to that of DE [84].

Spiral enteroscopy can be performed in post-gastric surgery patients and used for ERCP in surgically altered anatomy. Spiral-assisted ERCP (SE-ERCP) in patients with Roux-en-Y anatomy is comparable with SBE-assisted ERCP in terms of successful cannulation (40 and 48%, respectively) and therapy (89 and 100%, respectively), procedure time, and complications [85].

Spiral enteroscopy can be used in a retrograde approach to visualize the ileum. A newer modification of the overtube, Endo-Ease Vista Retrograde (Spirus Medical, Stoughton, MA), was demonstrated to have high success rate in intubation of the terminal ileum [86]. In a recent study of 22 patients who underwent retrograde spiral enteroscopy, the terminal ileum was intubated in all patients with median depth of insertion from the ileocecal valve of 100 cm (range 50–150 cm) [86]. Similar to DBE and SBE, prior VCE results seem helpful in determining the route of SE and increasing the diagnostic yield for spiral enteroscopy [87].

In 2013, a novel through-the-scope (TTS) single-balloon enteroscope system (NaviAid™ AB Advancing Balloon, Pentax Medical, Tokyo, Japan) was introduced. Through-the-scope balloon-assisted enteroscopy (TTS-BAE) is a novel technique that utilizes a standard endoscope with a 3.7 mm working channel without the need for an overtube. The TTS balloon system includes a single-use latex-free balloon catheter designed for anchoring in the small bowel and a balloon inflation/deflation system. Once the ligament of Treitz or the terminal ileum is reached, the balloon is advanced in front of the endoscope until resistance is felt. The balloon is then inflated and the endoscope is advanced forward while applying traction on the balloon [88]. Once the balloon is reached by the endoscope, it is deflated and this push-and-pull technique is repeated to advance through the small bowel. The catheter may be removed and reinserted to allow for therapeutic intervention while maintaining the endoscope position [89] (Figs. 13.7 and 13.8).

Procedure time to point of maximal insertion is much shorter (~15.5 min) than the other forms of deep enteroscopy (~45–60 min) with comparable diagnostic yield (45%) and depth of insertion (~158 cm from the pylorus or 110 cm proximal to the ileocecal valve) [27, 89, 90]. No complications have been reported to date in the few studies of TTS-BAE [89, 90]. It may be particularly useful in assisting ERCP and metallic stent deployment in patients with strictures.

The two most commonly used enteroscopic methods in current practice are double-balloon enteroscopy and single-balloon enteroscopy. Both of these not only have excellent depth of insertion, but also stabilize the intestine for good endoscopic control during interventions. There are numerous head-to-head studies comparing these two; however, many of these studies are not well done and difficult to compare. Most studies show that DBE can be advanced a bit further than SBE, but this is still debatable (Table 13.3) [73, 74, 81, 83, 91]. Procedure duration is shorter for SE than for DBE and SBE. Although the rate of successful complete enteroscopy appears superior for DBE compared with SE and SBE, this result does not necessarily translate to an increase in diagnostic or therapeutic yield.