The standard procedure for removing bile duct stones is endoscopic removal using endoscopic retrograde cholangiopancreatography (ERCP). However, removing common bile duct and/or intrahepatic stones from a patient with a surgically altered anatomy can be challenging. Recently, a balloon enteroscope with a wide channel, which can be used with a variety of devices, has become available. Stone removal using balloon enteroscopy-assisted ERCP (BEA-ERCP) has been reported to be safe and have a relatively high success rate.1 However, endoscope insertion and biliary cannulation may be unsuccessful, even when performed by experts, due to postoperative adhesions and long afferent limbs. In such situations, percutaneous transhepatic biliary drainage (PTBD) has been performed as a salvage technique after a failed BEA-ERCP procedure; however, a decrease in the patient's quality of life remains an issue with this technique.

Endoscopic ultrasound-guided biliary drainage (EUS-BD) has emerged as an alternative method for salvaging an unsuccessful ERCP procedure, especially in the case of a malignant biliary stricture. Furthermore, in recent years, an EUS-guided antegrade intervention (EUS-AI), which is an antegrade treatment that uses a fistula that is created by EUS-BD, has attracted attention.2, 3 Compared with BEA-ERCP, PTBD, or surgery, EUS-AI has the advantage of a straightforward approach to the bile duct, a short procedure time, and the avoidance of several issues associated with an external drainage catheter. In fact, a previous study on drainage techniques for patients with a surgically altered anatomy showed that EUS-BD had a higher success rate and shorter procedure time than BEA-ERCP. However, the adverse event rate was significantly higher for EUS-BD (20% vs. 4%, respectively; P = 0.01),4 and the available devices were limited compared with BEA-ERCP. Therefore, BEA-ERCP, which is less invasive and safer, should be considered the first-line treatment for benign biliary diseases such as bile duct stones, and EUS-AI should be selected as an alternative treatment.

Endoscopic ultrasound-guided antegrade stone removal is a type of EUS-AI, and it has been increasingly reported as a salvage technique that can be used after an unsuccessful stone removal using BEA-ERCP.5 With EUS-guided antegrade stone removal, the intrahepatic duct is punctured using a fine needle aspiration needle, and a guidewire is advanced through the ampulla into the duodenum. Subsequently, the ampulla is dilated using a dilatation balloon catheter, and the bile duct stones are pushed out across the ampulla in an antegrade fashion with an extraction balloon catheter. Following the complete removal of the stones, a temporary nasobiliary drainage tube or plastic stent is often placed into the bilioenteric fistula to prevent bile leakage.

The authors of a multicenter retrospective study of EUS-guided antegrade stone removal of bile duct stones for patients with a surgically altered anatomy reported a success rate of 72% and an adverse event rate of 17%.6 Although these results suggest that EUS-guided antegrade stone removal is an effective treatment for bile duct stones, there are some limitations. In cases where the bile duct is not completely obstructed, the EUS approach may be challenging because of insufficient dilatation of the intrahepatic bile duct. Usually, a 19G needle combined with a 0.025-inch guidewire is used; however, in such cases a 22G needle combined with a 0.018-inch guidewire is preferred. Recently, a novel 0.018-inch guidewire with improved stiffness was developed. Using a 22G needle combined with this novel 0.018-inch guidewire appears to be a safer and more feasible approach.7

Ampullary intervention is limited to papillary balloon dilation. Therefore, if the stones are larger than the size of the dilation balloon, biliary lithotripsy is required. However, this may prolong the procedure time and increase the risk of bile leakage. Furthermore, the limited availability of devices makes stone removal technically difficult.

A two-step approach has been devised as a treatment option to resolve these limitations. In the first session, EUS-guided hepaticoenterostomy is performed to create a fistula between the enteric canal and left intrahepatic bile duct. In the second session, antegrade stone removal is performed after the fistula has matured. Creation of a mature fistula reduces the risk of bile leakage. A mechanical lithotripter and peroral cholangioscope can be inserted easily through the bilioenteric fistula, allowing for electrohydraulic or laser lithotripsy under direct vision. This treatment strategy provides a safe and high rate of stone removal, even for large stones.5

However, stone extraction for patients with hepaticojejunostomy strictures may be challenging when pushing stones out into the intestine, even after dilatation of the stricture has occurred using a balloon catheter, because it is difficult to match the force required to push stones out in line with the bile duct axis.

To overcome this difficulty, Ogura et al.8 has proposed transluminal stone extraction in this issue of Digestive Endoscopy. Transluminal stone extraction has several advantages over antegrade stone removal. First, transluminal stone extraction does not involve treatment via the ampulla; therefore, there is no risk of acute pancreatitis. In addition, this procedure does not require dilatation of the ampulla or anastomosis, nor does it induce dilatation-associated bleeding from the ampulla, which is challenging to detect early and cannot be stopped endoscopically. Considering these factors, transluminal stone extraction is likely to be of greater benefit to patients. The available stone extraction devices are designed to apply a pulling force under ERCP guidance, as antegrade stone removal using a pushing force is not suitable. Transluminal stone extraction is performed through the application of a pulling force, as well as with ERCP, which facilitates stone extraction, even in the presence of a severe anastomotic stricture.

However, the left intrahepatic bile duct has many branches, and stones can escape into these branches when they are pulled out into the stomach and jejunum using conventional devices, such as balloon or basket catheters. Once stones have migrated into these branches, extraction becomes extremely challenging.

Ogura et al.8 described the clinical use of a novel spiral basket catheter (VorticCatch V; Olympus Medical Systems, Tokyo, Japan) to prevent stone migration during transluminal stone extraction. Compared with conventional basket catheters, the VorticCatch V basket catheter features a smaller winding pitch and adhesion to the bile duct wall. Small bile duct stones can easily be captured simply through pulling the catheter back while opening the basket catheter, as the specialized shape of this type of basket catheter enables reliable stone extraction. However, this device involves the risk of basket impaction due to the small bilioenteric fistula diameter. To overcome this risk, stones should be crushed to a size suitable for the fistula diameter, after which extraction can be performed.

Antegrade stone removal and transluminal stone extraction may be more effective procedures for treating bile duct stones in patients with a surgically altered anatomy. However, further prospective comparative evaluations with a larger number of patients are needed.

Recently, the authors of a retrospective study compared the ability of both BEA-ERCP and EUS-guided antegrade stone removal to remove bile duct stones in patients with a surgically altered anatomy, and they found that the technical and complete removal rates were similar between the groups.9 However, when comparing patients with Roux-en-Y reconstruction in the EUS-guided antegrade stone removal and BEA-ERCP groups, the EUS-guided antegrade stone removal group exhibited a significantly higher technical success rate (92.3% vs. 60.0%, P = 0.04) and shorter procedure time (48.6 ± 12.9 min vs. 85.9 ± 34.0 min, P = 0.0008) than the BEA-ERCP group. Therefore, based on these results, EUS-guided antegrade stone removal may be a preferable option for patients with Roux-en-Y reconstruction. However, if there are non-dilated left intrahepatic ducts, right intrahepatic duct stones, or double right and left biliary anastomoses, PTBD or BEA-ERCP is recommended because EUS-guided biliary access is challenging.

In conclusion, although the evidence remains limited, EUS-guided antegrade stone removal appears to be a promising minimally invasive treatment option for removing bile duct stones in patients with a surgically altered anatomy. Currently, this procedure is considered an alternative that can be used after a failed BEA-ERCP procedure, although it may become a first-line treatment as dedicated devices are developed. Prospective randomized control trials should be conducted to further assess the safety, efficacy, and standardization of the procedure.

Author declares no conflict of interest for this article.