Reply to Kadayifci et al.

We appreciate the comments made by Dr. Kadayifci regarding our study in which we concluded that complete endoscopic treatment with a single catheter is more likely when choosing a balloon catheter over a basket catheter for the extraction of bile duct stones ≤ 10 mm [1].

In the basket group, the basket catheter was switched to a balloon catheter when the endoscopist had judged the duct clearance to be complete by the basket catheter. First, the balloon was inflated at the perihilar bile duct and pulled to the bottom of the bile duct, and then balloon-occluded cholangiography (BOC) was performed. During this procedure, if a stone emerged from the papilla of Vater, this was judged to be “incomplete clearance.” In addition, when a defect on BOC was confirmed to be a stone by subsequent endoscopic observation, the outcome was also judged to be “incomplete clearance.” Therefore, “residual stones on BOC (n = 9)” were confirmed during this procedure. These failure cases meant that duct clearance had not been completed by basket catheter alone. “Complete clearance by the assigned catheter” in the basket group represented the result obtained by the basket catheter alone, not by the basket catheter plus the balloon catheter. Therefore, we think that using the balloon after the basket for stone extraction was not a confounding factor of our study.

As mentioned by Dr. Kadayifci, it is sometimes difficult to check stone removal by direct endoscopic observation after balloon sweep of the duct. Therefore, the performance of the balloon catheter may be overestimated. The actual success rate of each catheter might be lower than the rates determined in our study because BOC and balloon sweep were used to confirm duct clearance in both groups. For true comparison of the two catheters, other modalities, such as peroral cholangioscopy, should be used to evaluate the efficacy of individual catheters. However, it was not realistic to use cholangioscopy to evaluate residual stones in our study because participants included patients with normal common bile ducts, with diameters ≤ 8 mm in general. In addition, evaluating the end point by the same method in both groups is crucial in a randomized controlled trial. When considering clinical trial feasibility, BOC was selected to evaluate the end point in both groups to minimize the methodological bias. However, we identified this issue as a limitation of our study.

• References

• 1 Ishiwatari H, Kawakami H, Hiroyuki H et al. Balloon catheter versus basket catheter for endoscopic bile duct stone extraction: a multicenter randomized trial. Endoscopy 2016; 48: 350-357