Endoscopic retrograde cholangiopancreatography (ERCP) has long been established as a standard procedure. The success rate of ERCP-related procedures in patients with normal anatomy has been reported to be approximately 95% [1]. In contrast, ERCP in patients with surgically altered anatomy (SAA) is considered particularly challenging. SAA includes Roux-en-Y gastrectomy (including Roux-en-Y gastric bypass), hepaticojejunostomy with Roux-en-Y (with preservation of the stomach), pancreaticoduodenectomy, and Billroth II gastrectomy. Multiple technical hurdles must be overcome to complete the intended procedure. First, the distance from the afferent loop to the target site (e.g., the papilla or hepaticojejunal anastomosis) is longer than in normal anatomy, particularly in Roux-en-Y anastomosis. Second, selective biliary cannulation in patients with a native papilla is difficult because the papilla is visualized in an inverted orientation and is often located in a tangential direction. Moreover, completing intended procedures such as stone extraction (including endoscopic sphincterotomy [EST]) and self-expandable metallic stent (SEMS) placement is particularly challenging. Over the past two decades, the success rate of intended procedures—particularly reaching the papilla or hepaticojejunal anastomosis in patients with SAA using conventional endoscopes such as the duodenoscope or pediatric colonoscope—has not been satisfactory [2,3]. Therefore, surgical intervention or percutaneous transhepatic biliary drainage (PTBD) was often selected as an alternative in cases of ERCP failure.

Double-balloon enteroscopy (DBE) was introduced into clinical practice in 2001 [4]. Since then, DBE and single-balloon enteroscopy (SBE)-assisted ERCP have been reported as preferred approaches in patients with SAA [5-8]. A systematic review and meta-analysis of SBE-assisted ERCP reported a pooled overall procedural success rate of 75.8% [9]. However, since those scopes have a working length of 200 cm and a working channel diameter of 2.8 mm, only a limited number of ERCP accessories are available. To overcome these limitations, short-type DBE and SBE (short SBE), with a working length of approximately 150 cm and a 3.2-mm working channel, have been introduced (Fig. 1) [10]. Short SBE has expanded the range of accessories available for procedures such as stone extraction and SEMS placement [11,12]. It has been reported that the overall procedural success rate of short SBE-assisted ERCP ranges from 70.4% to 85.9% (Table 1) [13-16]. A recent multicenter study of short SBE-assisted ERCP in patients with SAA reported overall procedural success and adverse event rates of 74.9% and 7.7%, respectively [17]. Moreover, studies identified several factors associated with procedural failure, including Roux-en-Y anastomosis, pancreatic indications, and malignant disease [15-17].

In addition, several new technologies and devices have recently been introduced to help manage difficult cases. In this review, we provide technical tips for short-type SBE–assisted ERCP in patients with SAA, with the aim of improving procedural success rates and reducing adverse events, while also highlighting recent advances in technology and device development.

Before starting scope insertion, it is essential to review each patient’s surgical records to identify the type of reconstruction and the bifurcation between the efferent and afferent limbs. At our facility, an attachment cap is placed on the tip of the scope in all cases. This facilitates not only scope insertion but also selective biliary cannulation. In fact, it has been reported that the absence of an attachment cap is one of the factors associated with overall procedural failure [15]. Carbon dioxide insufflation is also useful during scope insertion. Patients are usually placed in the prone position to reduce the risk of pulmonary aspiration. Fluoroscopy is used during scope insertion to confirm the direction of scope advancement.

The principle of deep insertion using SBE is the so-called “pushand-pull” method. After advancing the scope to pass through bends in the small intestine, the scope is then pulled back to pleat and shorten the intestine. During this shortening maneuver, the balloon attached to the tip of the overtube is used. Before shortening, it is important to advance the overtube as close as possible to the tip of the scope. While advancing the overtube, the balloon should be deflated. However, as the overtube is advanced, the scope itself also tends to move forward, which is inefficient. Therefore, the scope should be gently pulled back while the overtube is advanced (Fig. 2). During shortening, the balloon is inflated to fix the small intestine, while the scope is pulled back using the scope’s angulation to hook the intestine and prevent scope withdrawal. This technique is particularly important in patients with hepaticojejunostomy and Roux-en-Y reconstruction with a preserved stomach, as the distance to the target site is long. In such cases, maximizing scope shortening is essential. Advancing the scope can sometimes be difficult when passing through a sharp flexure. Short SBE is equipped with a passive bending function, which allows the scope to pass smoothly through angulated segments and advance forward [8]. When difficulty persists despite using this function, changing the patient to the left lateral position or abdominal compression is effective.

In patients with Roux-en-Y gastric bypass and hepaticojejunostomy with Roux-en-Y seem to be difficult as the Roux limbs tend to be longer. In such cases, conventional SBE with a 200 cm working length is useful. We use this scope when the scope insertion using short SBE failed. Furthermore, malignant biliary obstruction cases tend to cause strong adhesion due to cancer so scope manipulation can be quite difficult. This can result in procedural failure. In such cases, it is difficult to complete the intended procedure by SBE-assisted ERCP. PTBD or endoscopic ultrasound-guided biliary drainage (EUS-BD) could be good alternatives in such cases.

When advancing the scope to the target site, it is important to keep in mind that intestinal perforation can occur due to tight adhesions, particularly near the target site. A multicenter study reported an intestinal perforation rate of 1.9% [17]. It has been reported that Billroth II patients with a short afferent loop between the gastrojejunal anastomosis and the ligament of Treitz have the highest risk of perforation, as this segment tends to be subjected to strong forces during scope advancement [18]. Careful scope manipulation is required in such cases.

In normal anatomy, the bile duct is located between the 11 and 12 o’clock positions of the papilla. In contrast, in SAA such as Roux-en-Y or Billroth II gastrectomy, the bile duct is located between the 5 and 6 o’clock positions because the papilla appears inverted. Since the catheter emerges from the 8 o’clock position when using SBE, positioning and fixing the papilla at the 11 o’clock position on the endoscopic view is considered appropriate. Moreover, because SBE (as well as DBE) lacks an elevator function, a straight catheter (without pre-shaping) should be used for selective biliary cannulation. In difficult cases, a bendable catheter can also be useful for adjusting the direction of bile duct access.

When the scope reaches the papilla, it is often positioned tangentially, particularly in patients with Roux-en-Y gastrectomy. In such situations, adopting a retroflexed position is very useful [19]. To achieve retroflexion, the endoscope is advanced while applying the up angle at the inferior duodenal flexure. The scope is then positioned in a J-turn to obtain a better view of the papilla. As a result, this improved visualization facilitates a higher success rate of selective biliary cannulation (Fig. 3). It has been reported that, in multivariate analysis, the retroflex position was more likely to result in successful selective biliary cannulation in patients with Roux-en-Y gastrectomy [20]. The success rate for achieving the retroflex position was reported as around 60% [20]. It would depend on the space of the duodenum and the intestinal adhesion. Therefore, if making the retroflex position seems too difficult, it should be omitted, otherwise intestinal perforation can occur.

In cases of difficult selective biliary cannulation, pancreatic duct–assisted techniques, such as the double-guidewire method [21], can be useful, similar to ERCP in patients with normal anatomy. In addition to the double-guidewire method, pancreatic duct stent–assisted biliary cannulation [22], or cannulation using a doublelumen cannula [23] can also be effective. As the selective biliary cannulation in patients with SAA (especially, with native papilla) tends to be difficult, many attempts and taking long time for selective biliary cannulation could cause post-ERCP pancreatitis so it is important to make a decision to abort the procedure after a certain amount of time for safety. If it is still unsuccessful, reattempting cannulation on another day, or the rendezvous technique or direct drainage using an alternative method, such as PTBD or EUS-BD should be selected depending on the patient’s condition or the content of procedure.

Selective biliary cannulation in patients with hepaticojejunal anastomosis (e.g., hepaticojejunostomy with Roux-en-Y or pancreaticoduodenectomy), is generally straightforward once the orifice of the anastomosis is identified. Cannulation failure most often occurs when the anastomotic site cannot be reached or located. In cases where the scope reaches the site but the orifice is difficult to identify, the presence of scar tissue around the opening may help in locating the anastomosis.

After successful cannulation, subsequent procedures such as stone extraction and SEMS placement remain challenging. Before performing these interventions, EST, endoscopic papillary balloon dilation, or endoscopic papillary large-balloon dilation (EPLBD) is usually required. EST is considered particularly difficult in these cases because the cutting direction is usually either opposite to that of standard sphincterotomy or more tangential. In addition, there have historically been few dedicated devices available to allow a safe incision in the correct direction of the bile duct. Recently, a novel rotatable sphincterotome (ENGETSU; Kaneka Corp., Osaka, Japan) was launched, which allows the blade to be rotated in the correct direction for EST by turning the handle [24-26]. This allows for greater rotation than other sphincterotomes, as required by the endoscopist (Fig. 4).

When performing stone extraction, it is important to adequately loosen the papillary orifice by performing EST and/or EPLBD. In patients with SAA, the force for stone extraction is mainly applied by withdrawing the scope. Because this force is difficult to control, there is a risk of sudden scope passage through the papilla, which may cause intestinal perforation if the orifice has not been loosened enough. Several studies have evaluated factors affecting complete stone extraction. It has been reported that failure to achieve the retroflex position and common bile duct diameter ≥14 mm were factors of unsuccessful stone extraction [27]. It has also been reported that larger bile duct diameter (mean; 15.9 mm) affected the unsuccessful stone extraction [12]. When it seems difficult to complete stone extraction just by SBE-assisted ERCP, a combination of stone extraction added by EUS-BD route may be a good alternative [28,29].

As the short SBE has a 3.2 mm working channel in diameter, it enables us to place various SEMS in patients with SAA [11]. Almost all SEMSs which are used in patients with normal anatomy can be used. We usually place covered SEMS in patients with distal malignant biliary obstruction across the papilla after performing EST and uncovered SEMS in patients with hilar malignant biliary obstruction (Fig. 5). It has been reported that clinical success and recurrent biliary obstruction rate in patients with SAA who were placed SEMS were similar to those in normal anatomy [11,30].

In addition to dedicated sphincterotomes, newer technologies and devices have become available in clinical practice to improve the overall procedural success rate.

Texture and color enhancement imaging (TXI) is incorporated into a new-generation image-enhanced endoscopy processing system (EVIS X1; Olympus Marketing, Tokyo, Japan) that optimizes three mucosal surface elements: structure, color, and brightness [31]. This makes structural changes clearer compared to those using conventional white light imaging [32-34]. Therefore, TXI can improve the ability of endoscopists to identify the orifice of the papilla and improve cannulation success (Fig. 6) [35]. While selective biliary cannulation in patients with a native papilla is considered challenging, cannulation of the pancreaticojejunal anastomosis is also regarded as a big challenge, particularly in patients with an anastomotic stricture [36]. To deal with those cases, in addition to TXI [33], gel immersion technique to visualize oozing pancreatic juice is also effective [37].

Recently, thin cholangio-pancreatoscopes (8-9 Fr) have been introduced in Japan, enabling peroral cholangioscopy, peroral pancreatoscopy, and related procedures such as biopsy and cholangioscopy-guided lithotripsy (Fig. 7) [38-41]. These recent technological and device advancements are highly beneficial, and endoscopists should remain up to date with them.

In this review, we have outlined technical tips for SBE-assisted ERCP, focusing on scope insertion, selective biliary cannulation, and subsequent procedures, while also highlighting recent advancements in technologies and devices. We hope these tips will help endoscopists performing BE-assisted ERCP. Recently, EUS-BD has been reported as another alternative with shorter procedure duration. However, due to the limited choices for the accessories, even EUS-BD performed by the experienced endoscopists, it could cause severe adverse events such as bile leak or stent migration into the abdominal cavity. In contrast, DBE and SBE-assisted ERCPs are more predictable and safer because ERCP is a well-established procedure and already has many dedicated accessories. Therefore, the choice between BE-assisted ERCP or EUS-BD should depend on postoperative reconstruction, patient condition, and more importantly the endoscopist’s experience.