3 | DISCUSSION
There are 3 reports in the literature on cases of CBD stones with distal CBD strictures that were treated using CSEMS (Table 1). However, two case series did not mention the details of the cases with CBD stones and distal CBD strictures. A case series by Cerefice et al. targeted cases with the CBD stones that were difficult to remove using conventional endoscopic methods.8Another case series by García-Cano et al. targeted older patients who had difficulty tolerating endoscopic lithotripsy due to the long duration required by the procedure.10
A case report by Okabe et al. described a case of CBD stones and distal CBD stricture due to CP.9 In that case, the CBD stones remained in the biliary duct and the upper portion of the CSEMS, and the distal biliary stricture did not improve despite CSEMS placement for 14 days. On the contrary, the CBD stones had spontaneously disappeared in our case and, the distal biliary stricture had also slightly improved by the placement of the CSEMS for only 7 days. This observation indicates that the new CSEMS BONASTENT M-intraductal (Standard Sci Tech) has strong dilation ability. The stent’s dumbbell shape was thought to slightly prevent stent migration and transmit dilation forces to the CBD stricture.
The CSEMS should be placed for a longer duration to avoid recurrence of the CBD stones. Although, CSEMS dilated the distal CBD stricture, the distal CBD remained thin (Fig. 3c). In the past reports, variations were seen in the duration and effectiveness of the CSEMS placement for CBD strictures secondary to CP. Cahen et al. reported six cases that received CSEMS for CBD stricture with CP.20 They reported the CSEMS removal time to be 3–6 months and that 66% of the CBD stricture showed improvement. Lalezari et al. reported a case with CP in which the CBD was dilated by CSEMS.21 In this report, the CSEMS was placed for 63 days, and the CBD stricture had improved. Haapamäki et al. had conducted a randomized controlled study on the effectiveness of multiple plastic stents versus the CSEMS in treating biliary stricture with CP.22 In this study, CSEMS was removed 6 months after randomization, and the two-year stricture-free success rate was 92% (24/26). Although, the targets were not CP patients alone, Park et al. raised the duration of CSEMS placement to ≥ 120 days as a factor for CBD stricture resolution.23
However, complications such as migration and embedding have been reported when the CSEMS was left in place for a longer duration.10,20,23-25A new dumbbell-shaped CSEMS is thought to be useful in preventing misregistration. The duodenal tip of the dumbbell shape can prevent the embedding and migration into the biliary tract superiorly and while the hilar tip can prevent duodenal migration. If the new dumbbell-shaped CSEMS migrates into the biliary tract superiorly, removing the stent is thought to be easier than removing other types of the CSEMSs, primarily because the dumbbell-shaped CSEMS becomes narrower by pulling a string that is attached at the duodenal tip (Figure 2). Park et al. described that migration of the CSEMS is a risk factor that prevents benign CBD stricture resolution.23Therefore, the dumbbell shape is expected to prevent misregistration and dilate the CBD stricture effectively. In fact, in this case, the CBD stricture was slightly dilated after CSEMS placement for only 7 days.
In conclusion, the new dumbbell-shaped CSEMS is efficient in removing the CBD stones with CBD strictures that occur due to CP. The stent might have the potential to prevent positional displacement and contribute to improved CBD stricture.