Will endoscopic ultrasound-guided bile duct drainage replace ERCP?

Endoscopic ultrasound (EUS)-guided transmural drainage has become an established endoscopic intervention for the drainage of peripancreatic and other fluids that collect adjacent to the gastrointestinal tract. During the past decade, the use of EUS-guided drainage has expanded to the biliary and pancreatic duct systems. Since Giovannini et al. [1] first reported EUS-guided bile duct drainage (EUS-BD) in 2001, it has been increasingly performed and has been shown to be a technically feasible procedure, with high success rates (75 % – 100 %) in clinical trials [2]. In selected cases, EUS-BD can replace traditional percutaneous intervention in patients with distal malignant biliary obstruction and failed endoscopic retrograde cholangiopancreatography (ERCP); EUS-BD can be performed during the same endoscopy session as ERCP and avoids the inconvenience of external drainage [3]. However, there is controversy over whether EUS-BD can replace percutaneous transhepatic biliary drainage as the primary modality for biliary obstruction and failed ERCP. Furthermore, some endoscopists suggest that EUS-BD may replace the standard transpapillary ERCP as the first-line drainage procedure for malignant biliary obstructions [4].

In the current issue of Endoscopy, Kawakubo et al. [5] report on the use of EUS-guided choledochoduodenostomy (CDS) using a self-expanding metallic stent (SEMS) as the primary treatment in patients with distal malignant biliary obstruction. The researchers compared the procedure with a historical control group that had undergone standard transpapillary ERCP with SEMS placement. The clinical success rates, overall adverse events, and reintervention rates were equivalent in the two groups. However, EUS-CDS was a shorter procedure than ERCP (19.7 vs. 30.2 minutes; P < 0.01) and had no post-procedure pancreatitis. In another study in the current issue of Endoscopy, Ogura et al. [6] compared the efficacy of EUS-CDS and EUS-guided hepaticogastrostomy (HGS) in patients with malignant bilio-duodenal obstruction. They performed EUS-BD (CDS or HGS) as the primary procedure with no attempt at a transpapillary approach. In malignant duodenal obstruction, EUS-HGS resulted in longer stent patency than EUS-CDS (duodenal stent, 113 vs. 34 days, P = 0.046; biliary stent, 133 vs. 37 days, P = 0.045) and fewer adverse events.

As discussed in these two articles, EUS-BD is a rapidly developing and expanding endoscopic procedure that is drawing much interest from interventional endoscopists. Can it become a standard endoscopic procedure that replaces percutaneous biliary drainage and even transpapillary ERCP? First, consensus on some important issues in EUS-BD, such as the optimal stent or tract dilation method, should be established to standardize this procedure. Specialized devices and accessories should be developed to maximize efficiency while minimizing adverse events, including a modified EUS endoscope and optimal needles and guidewires. The stent is the most important device in the final step of EUS-BD. Currently, a covered metallic stent that should prevent bile leakage is preferred. However, the “tubular” SEMS was originally designed for transpapillary drainage through longitudinal ductal strictures, not for connecting the gastroduodenal tract with the biliary tree. The placement of a tubular SEMS that crosses two different anatomical structures involves a risk of stent migration or the leakage of bile or gastroduodenal contents, which may be fatal. Kawakubo et al. also used a partially covered SEMS, and experienced two stent migrations and other adverse events (27 %, 7/26), including one biliary peritonitis.

New metallic stents developed specifically for EUS-guided drainage by connecting and fusing the lumens of two different organs have recently been introduced; these are “lumen-apposing” stents rather than conventional tubular stents [7] [8] [9]. EUS-BD with a lumen-apposing stent should decrease stent migration and leakage compared with conventional tubular stents [10] [11] [12]. However, this should be validated in more extensive studies. Currently, no lumen-apposing stents are available for EUS-HGS.

A successful EUS-BD procedure involves many technical steps, including puncture of the target site, needle exchange, and one or two attempts at tract dilation and stenting procedures. For a successful procedure, each step should be successful. If the procedure fails after tract dilation, it may lead to serious complications. The recently introduced lumen-apposing stent with a novel cautery-tipped stent delivery system (Hot AXIOS; Boston Scientific Corp., Marlborough, Massachusetts, USA) enables tract dilation and stenting in a single step [13]. It should shorten the procedure and lead to safe, effective EUS-BD.

There is also no standardized method for tract dilation, which is the critical step during EUS-BD. Currently, the use of a cystotome is preferred for tract dilation and should be safer than a needle-knife because the diathermic metal tip of the cystotome is advanced straight over a guidewire.

EUS-BD is commonly performed with an “oblique-viewing” echoendoscope, which leads to technical difficulty during EUS-BD, particularly in the final stenting step. Endoscopic visual guidance is needed during proximal deployment of a metal stent. However, oblique-viewing makes endoscopic observation and perpendicular insertion of a stent difficult. Hara et al. [14] reported the first successful EUS-CDS using a forward-viewing echoendoscope, with technical and clinical success rates of 94 % (17/18) and 94 % (16/17), respectively. Although a “forward-viewing” echoendoscope may overcome some difficulties, the available echoendoscope is limited by a narrow echo window (90°) and no elevator, resulting in less pushability. Further improvement and development of echoendoscope systems are required for safe, effective EUS-BD.

What are the current indications for EUS-BD given these technical issues? Who can perform EUS-BD in patients with optimal indications? For EUS-BD to be the primary endoscopic procedure, it should be acceptable to all biliary endoscopists, not just experts. As Kawakubo et al. [5] and Ogura et al. [6] have stated, EUS-BD should currently be performed by expert endoscopists for ERCP and EUS procedures. Kawakubo et al. [5] reported that the advantages of EUS-CDS compared with traditional transpapillary bile duct drainage by ERCP are the short procedure time and no risk of pancreatitis. However, ERCP is the standard procedure, with documented safety and efficacy. When expert endoscopists perform ERCP, the procedure time is shortened and complications are minimized.

Although pancreatitis is the main problem associated with ERCP, the incidence is 8 % – 10 %, and the rate of severe pancreatitis is only 0.5 % –1.0 % [15]. In Kawakubo et al. [5], pancreatitis developed in 16 % (9/56) of the transpapillary bile duct drainage group, but it was self-limiting and mild in eight patients and no severe forms occurred. Many studies have shown good results in minimizing post-ERCP pancreatitis by using rectal indomethacin [16] and prophylactic pancreatic stenting [17]. Biliary peritonitis and liver abscess, which were not observed in the transpapillary bile duct drainage group, developed in the EUS-CDS group. Therefore, the safety of EUS-BD should be validated in more extensive prospective studies.

In terms of technical and instrument issues, dedicated, specialized duodenoscopes with various accessories and devices, including stents, have been developed and are available for ERCP-guided transpapillary bile duct drainage. Transpapillary bile duct drainage is a useful primary modality not only for inoperable malignant biliary strictures but also for benign biliary strictures [18] or preoperative biliary drainage. EUS-CDS is usually performed for distal malignant biliary strictures and EUS-HGS for strictures at or below the level of the left hepatic duct. Transpapillary bile duct drainage can be performed for strictures at most levels requiring drainage, and allows single or multiple stenting for targeted bile ducts [19].

There are insufficient data on stent patency in patients who have undergone EUS-BD. Kawakubo et al. [5] reported that the reintervention rate was 20.0 % in the EUS-CDS group within a median follow-up of 298 days, although data on definite stent patency were not available. In comparison, Ogura et al. [6] reported that the median stent patency was only 37 days in their EUS-CDS group. In another study, although combined duodenal obstruction was present, stent patency was shorter than reported rates in patients with ERCP-guided transpapillary bile duct drainage [20].

Is EUS-BD acceptable for preoperative bile duct drainage in patients with operable malignant bile duct obstruction? In Kawakubo et al. [5], curative surgery with no significant perioperative adverse events was performed in one patient who underwent EUS-CDS. However, the safety of preoperative EUS-CDS is questionable and should be verified. Currently, EUS-BD is indicated in patients with malignant biliary obstructions that are histologically confirmed and nonresectable.

Will EUS-BD replace ERCP-guided transpapillary bile duct drainage in patients with an ampulla of Vater obscured by malignant biliary-duodenal obstruction? EUS-BD is obviously a useful alternative when the major papilla is not accessible because of combined malignant duodenal obstruction. EUS-CDS may be impossible, depending on the location and degree of duodenal obstruction [21]. EUS-HGS may be preferred in these situations because it has longer stent patency than EUS-CDS (median 113 vs. 34 days), according to the retrospective study by Ogura et al. [6]. However, the Ogura study included a higher proportion of patients with existing type II duodenal strictures in the EUS-CDS group (46 % vs. 19 %), although these differences were not significant. Selection bias can influence the findings of biliary stent patency. Therefore, prospective studies should confirm whether EUS-HGS is indeed better than EUS-CDS in patients with combined bilio-duodenal obstruction.

In conclusion, the replacement of traditional ERCP-guided transpapillary bile duct drainage with EUS-BD could be considered after the improvement of a dedicated echoendoscope, accessories, and devices including specialized stents, and standardization of the procedure protocol. More extensive prospective studies are needed to confirm the safety, efficacy, long-term outcomes, and reintervention results. Currently, the appropriate place for EUS-BD is as a rescue endoscopic procedure if ERCP-guided transpapillary bile duct drainage fails.

• References

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