Biliary drainage through endoscopic retrograde cholangiopancreatography (ERCP) is the standard therapeutic approach for malignant distal biliary obstruction (MDBO). However, conventional ERCP can be challenging in patients with surgically altered anatomy, pyloric/duodenal obstruction, or failed biliary cannulation. Previously, percutaneous transhepatic biliary drainage (PTBD) was preferred in these cases, but since the development of endoscopic ultrasound (EUS), EUS-guided biliary drainage (EUS-BD) has been increasingly performed.^1,2

There are several types of EUS-BD procedures depending on the access routes and methods of clinical practice: EUS-assisted rendezvous (EUS-RV), EUS-guided antegrade stenting (EUS-AGS), EUS-guided choledochoduodenostomy (EUS-CDS), and EUS-guided hepaticogastrostomy (EUS-HGS). Each procedure may be selected based on the conditions of patient and their healthcare providers. The current article provides a concise review of the latest practices and techniques of EUS-BD procedures for MDBO.

EUS-RV technique is to obtain an access route for ERCP in case of failed biliary cannulation. Bile duct puncture can be performed usually in the duodenal bulb or left intrahepatic bile ducts (IHDs) to advance the guidewire across the papilla for subsequent ERCP. A recent guideline advocates an EUS-RV procedure after the second ERCP failure especially in the cases of benign biliary diseases and normal gastrointestinal anatomy.² The reported overall success rate of EUS-RV was 73%–80%.^3,4 The main reason for its failure was the inability to pass the guidewire through an obstruction or the papilla. Failed cases can be salvaged with a percutaneous approach, but EUS-guided hybrid rendezvous technique was recently introduced as an alternative salvage method for standard rendezvous with IHD approach.⁵ A 6-french dilator is placed in the biliary system for better guidewire manipulation during the entire procedure of the hybrid technique. The overall success rate of EUS-RV combined with hybrid technique was improved up to 90%.⁵ For the target bile duct with a smaller diameter, a thinner 22G needle may be preferred over a 19G needle.⁶

EUS-AGS is the method of placing a stent through the stricture or papilla to the duodenum, approaching from the IHD. One advantage of EUS-AGS is decreased bile leakage from the IHD to the stomach.⁷ However, when stent placement fails, the risk of bile leakage may be of concern. Then, EUS-HGS or PTBD can be performed as a salvage method.⁸ However, reflux of duodenal contents such as food material can lead to stent dysfunction due to sludge formation or ascending infection.⁹ Recently, the method of placing EUS-guided antegrade covered metal stent with long duodenal extension was introduced to prevent reflux cholangitis and tumor in-growth.¹⁰ This method showed acceptable clinical outcomes (the technical and clinical success rates were 96% and 84%, respectively) with a low reintervention rate (8.3%), but heightened rate of postprocedural pancreatitis (24%) in patients with non-pancreatic cancers.

A biliodigestive anastomosis is created with either a biliary metal stent or lumen-apposing metal stent (LAMS) in EUS-CDS. The overall technical success rate was 95.0%, and the overall clinical success rate was 97.0% in a review of the recent literature published between 2015 and 2020.¹¹ Several randomized controlled trials comparing EUS-CDS and ERCP for MDBO have recently been reported. Overall technical success rates for ERCP and EUS-CDS were 92.7% and 91.1%, respectively (P = 0.788). Overall clinical success rates for ERCP and EUS-CDS were 94.1% and 93.6%, respectively (P = 0.765).^12–14 A recent meta-analysis showed that significantly less reintervention was needed for EUS-BD than ERCP (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15–0.86).¹⁵

It may be difficult to seal the anastomosis adequately with a plastic stent or uncovered self-expandable metal stent (SEMS), increasing the risk of bile leakage.⁸ Thus, either fully covered SEMS (FCSEMS) or LAMS is preferred for EUS-CDS. Small caliber LAMSs are appropriate for an EUS-CDS procedure because the procedure usually causes the reduction of common bile duct (CBD) diameter and the use of larger caliber LAMSs may damage the CBD.⁸ Electrocautery-enhanced LAMSs have improved the performance of direct EUS-CDS by removing the need for accessory exchanges and reducing the risk of procedural failure. In the electrocautery-enhanced LAMSs, an electrocautery wire was added to the distal tip of the delivery catheter to apply cutting current that allows the passage of the device through the gastrointestinal and the bile duct walls, without the need for prior dilation.¹⁶ A recent meta-analysis on the efficacy of LAMS or SEMS for EUS-CDS revealed that the rates of clinical and technical success, post-procedure adverse events, and reintervention were similar across the two types of stents.¹⁷

When performing EUS-CDS using an electrocautery-enhanced LAMS, the use of free-hand technique is recommended.⁸ It allows direct access to the CBD without a guidewire. However, EUS-CDS with LAMS may be difficult for CBDs with small diameter because deployment of the distal flange of the stent may be difficult. Two procedural adjustments, performing LAMS deployment in a stepwise manner and advancing a guidewire through the LAMS-introducing catheter, may be considered to overcome this limitation.⁸

LAMS mal-deployment may lead to bile leakage, which can be addressed by performing EUS-RV with a FCSEMS, or EUS-AGS after LAMS removal.¹⁸ This salvage procedure can also be applied to a case of accidental portal vein puncture during an EUS-CDS procedure.¹⁹ PTBD should be considered if an immediate endoscopic salvage therapy fails.⁸

A recent guideline recommends the use of partially covered SEMSs or FCSEMSs in EUS-HGS, because of the difficulty in placement of double pigtail stents and the high risk of bile leakage of uncovered SEMSs.⁸ Single pigtail plastic stents were designed for an EUS-HGS procedure and excellent outcomes have been reported.^20,21 However, FCSEMS may migrate easily and obstruct distal bile duct branches causing cholangitis. Hence, some hybrid SEMSs have been advocated to overcome these limitations.^22,23 The hybrid SEMSs are partially covered SEMSs with anchoring flaps and they were developed to prevent stent migration. In a long-term follow-up study on the effectiveness of newly developed hybrid SEMS, stent migration was not observed during the follow-up period (median, 148.5 days), and the mean stent patency duration was 166.3 days.²³

Recently, a study prospectively compared the two conditions, 19G needle with a 0.025-inch guidewire and 22G needle with a novel 0.018-inch guidewire for EUS-HGS. Across the two conditions, outcomes were comparable, even in cases of insufficient IHD dilatation. Technical success rates were 100% and 88.9% in 19G and 22G needle group, respectively.²⁴ In a recent meta-analysis, high technical and clinical success rates were reported for both EUS-CDS and EUS-HGS. Compared with EUS-HGS, the pooled OR of EUS-CDS was 0.74 (95% CI, 0.33–1.65; P = 0.46) for technical success and 0.94 (95% CI, 0.56–1.59; P = 0.83) for clinical success.²⁵ EUS-CDS was associated with a moderately shorter procedure time (–2.68 min) and significantly fewer early adverse events than EUS-HGS (12.2% vs 17.5%; OR, 0.58; P = 0.02).

Stent malposition in EUS-HGS usually occurs when the proximal end of stent is deployed inside the peritoneal cavity, leading to fatal bile peritonitis.²⁶ To prevent this, an adequate level of tension can be applied to the delivery catheter and the echoendoscope can be retracted for ensuring the opening of the proximal end of stent in the stomach.⁸ When the proximal end of stent is entirely outside the gastric wall while the guidewire is intact, an attempt can be made to insert a new FCSEMS over the guidewire to connect the unsuccessfully deployed stent to the stomach. If this salvage procedure fails, an emergency surgery should be considered to alter or adjust the stent position.²⁷

A specific method of EUS-BD for MDBO following failed ERCP can be determined based on papilla accessibility and IHD dilation. If the papilla is accessible, a rendezvous drainage should be attempted first in consideration of the convenience of subsequent revision by ERCP. If the papilla is inaccessible, the approach route can be determined depending on whether the IHD is dilated. When the IHD is dilated, an intrahepatic approach is preferred. Otherwise, an extrahepatic approach may be preferred only in the absence of gastric outlet obstruction. For the optimal method selection, the experience of the clinicians and the resources of each healthcare institution need to be fully considered. A decision flowchart for the MDBO treatment approaches is presented in Fig. 1.

Figure 1. A decision flowchart for the treatment approaches in patients with malignant distal biliary obstruction. ERCP, endoscopic retrograde cholangiopancreatography; EUS-BD, endoscopic ultrasound-guided biliary drainage; EUS-RV, endoscopic ultrasound-assisted rendezvous; IHD, intrahepatic bile duct; EUS-AGS, endoscopic ultrasound-guided antegrade stenting; EUS-CDS, endoscopic ultrasound-guided choledochoduodenostomy; EUS-HGS, endoscopic ultrasound-guided hepaticogastrostomy; PTBD, percutaneous transhepatic biliary drainage.

The most basic and important treatment for MDBO is ERCP. When ERCP fails, numerous alternative approaches to PTBD can be considered thanks to the recent technical breakthroughs in EUS-BD. The current article offers a concise review of the up-to-date practices and techniques of EUS-BD procedures. More studies need to be conducted on the long-term follow-up results of various EUS-BD approaches, EUS-guided hepaticoduodenostomy, and the development of dedicated stents.

None.

No potential conflict of interest relevant to this article was reported.