Kotaro Takeshita ,Satoshi Asai,Naoki Fujimoto,Takumi Ichinona,Eisuke Akamine

Department of Gastroenterology, Tane General Hospital, Osaka 550-0025, Japan

TotheEditor:

Endoscopic retrograde cholangiopancreatography (ERCP) is one of the most important techniques for diagnosis and treatment in pancreatobiliary medicine.Post-ERCP pancreatitis (PEP) is a common complication of ERCP with incidence about 3.8%–15.1% [1–4].

The precutting technique,contrast injection into the pancreatic duct,prolonged cannulation and procedure times,sphincterotomy,and balloon dilation of the papilla are known procedural factors associated with a high-risk of PEP [5].However,the relationship between accessory tools and PEP rate is unclear.To the best of our knowledge,no study has compared the PEP rates from stone extraction using either a retrieval balloon or a basket catheter tool.Thus,this study was conducted to address this research gap.Furthermore,we hypothesized that stone extraction using a retrieval balloon could provide higher pressure to the papilla than that provided by a basket catheter.This suggests that using a retrieval balloon could be a risk factor of PEP.

Bile duct stones were removed via ERCP in 451 cases in our institution from April 2013 to April 2018.Of these cases,207 were excluded from this study for the following reasons:presence of bile duct stones>10 mm;involvement of cholangioscopy,endoscopic mechanical lithotripsy,or endoscopic papillary large balloon dilation;and rectal administration of indomethacin 100 mg before ERCP was performed to prevent PEP.Finally,244 cases were included in the study and were divided into the group that used a retrieval balloon as the first choice (Balloon group;n=107) and a group that used a basket catheter as the first choice (Basket group;n=137).Moreover,each group was further subdivided into a onedevice group and a multiple-devices group.Eventually,only a retrieval balloon was used for complete stone removal in 104 cases(BAL group) and only a basket catheter was used in 88 cases (BAS group).

All procedures were performed by doctors in our department.Doctors with<3 years of experience in performing ERCP procedures or who had performed<200 procedures were defined as trainees.The TJF–240,TJF–260V (Olympus,Tokyo,Japan),or EI–580BT (FUJIFILM,Tokyo,Japan) was used to perform ERCP.

The primary outcome of this study was PEP rate.PEP was diagnosed if there was onset of pain and serum amylase levels increased 24 h postoperatively.In cases where a decision of PEP was uncertain,a computed tomography examination was performed.The secondary outcomes were the occurrence of other complications and the total number of complications.

We expressed quantitative variables as mean ± standard deviation (SD) and used the Student’st-test to compare the results.We used the Chi-square test or Fisher’s exact test to compare qualitative variables,as appropriate.The occurrence of primary and secondary outcomes were compared between the two groups.Results are presented as relative risks with 95%confident interval (95% CI).All tests were two-sided,and aP-value of less than 0.05 was considered statistically significant.Analyses were performed using the EZR statistical software,which was freely available website software (http://www.jichi.ac.jp/saitama-sct/SaitamaHP.files/statmedEN.html) [6].

Informed consent was obtained from all patients before ERCP.This study was carried out in accordance with the Ethical Principles for Medical Research Involving Human Subjects outlined in the Helsinki Declaration of 1975 (revised in 20 0 0) and approved by the Institutional Review Board of our hospital (IRB number:201901–44).

The diameter of the largest stone was significantly larger in the BAS group than in the BAL group (6.3 vs.4.6 mm;P<0.01).Other characteristics were comparable between both groups (Table 1).In three cases in the BAL group (2.8%,3/107),a basket catheter was also used during ERCP,and in 49 cases in the BAS group (35.8%,49/137),a retrieval balloon was also used.The main outcome,PEP rate,did not differ significantly between the two groups (4.8% vs.3.4%;P=0.73).Other complications and the total complication rate were also comparable between those groups (Table 2).No significant differences were obtained in univariate analysis.

To our knowledge,this study may be the first study to compare PEP rates using retrieval balloons and basket catheters.The PEP rate was similar between the two groups and other complications were not significantly different.Therefore,this study could not provide sufficient evidence for a relationship between the choice of device for stone removal and the occurrence of PEP;however,the choice of device was likely not associated with the occurrence of PEP.

When the diameter of a bile duct stone is<10 mm,stone removal is generally performed using a retrieval balloon or abasket catheter without endoscopic mechanical lithotripsy.The choice of device for stone removal typically depends on the endoscopists [ 1,2 ].

Table 1 Patient characteristics.

Table 2 Outcomes of each group.

Two comparative randomized studies reported the rates of complete stone removal using retrieval balloons and basket catheters in one session [ 7,8 ].Ishiwatari et al.[7]reported that the retrieval balloon was more effective for stone extraction in a single session.Contrarily,Ozawa et al.[8]reported that both devices had comparable effectiveness.These studies reported that the PEP rate between retrieval balloons and basket catheters was not significantly different;however,neither study truly compared PEP rates for each device,as both devices were used for stone removal in some cases.

A previous study [9]reported the outcomes of antegrade stone removal via the percutaneous transhepatic cholangioductal drainage route using a balloon catheter.The PEP rate in this study was lower than that for extraction through the ERCP route,which indicated that the use of a retrieval balloon was probably not related to the occurrence of PEP.This supports the outcome of our study.

The sub-analysis performed in this study yielded notable results.We excluded cases in which we used both devices in one session to compare the true relationship between the use of the retrieval balloon or basket catheter and the PEP rate.The rate of the additional use of a retrieval balloon was significantly higher than that of a basket catheter.This means that the rate of complete stone extraction in one session using a single device with retrieval balloons was higher than that with basket catheters.A similar outcome was reported by Ishiwatari et al.[7].

The limitations of this study include the single-center retrospective design,relatively small number of cases,and heterogeneity of factors that could be associated with PEP between the two groups.There could also have been some selection bias,because the first-choice device for stone removal was dependent on the physician.In the future,large-scale,multicenter,randomized controlled studies are needed to validate our results.

In this study,the choice of device did not affect PEP occurrence.The sub-analysis showed that the retrieval balloon could be a better first choice for completing stone extraction in one session.

Acknowledgments

The authors thank Dr.Kosuke Ito,Hitomi Jimbo,and Kenji Matsuo for helping us complete this study.

CRediT authorship contribution statement

Kotaro Takeshita:Conceptualization,Writing -original draft.Satoshi Asai:Methodology,Supervision,Writing -review &editing.Naoki Fujimoto:Data curation.Takumi Ichinona:Investigation.Eisuke Akamine:Formal analysis.

Funding

None.

Ethical approval

This study was approved by the Institutional Review Board of Tane General Hospital (IRB number:201901–44).Written informed consent was obtained from all participants.

Competing interest

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.