## 4 Discussion  
In our study, the data were collected from patients (with or without acute cholecitis) who underwent therapeutic ERCP for choledocholithiasis. We found that the subgroup analysis (conducted after the publication of the Tokyo guidelines cut-off at the end of 2013) showed that the proportion of inpatients who had a cholecystectomy during the same hospitalization (defined as the early cholecystectomy group) had decreased from 63.13% to 47.19%. The percentage of patients who had an intermediate cholecystectomy had increased from 24.86% to 32.51%. In the delayed cholecystectomy group, the rate had increased from 12.01% to 20.3%. Since the 2013 Tokyo guidelines for the surgical treatment of acute cholecystitis advocated a different approach, depending on the grade of severity, new diagnostic criteria and surgical indications for surgeons have been established [12]. Laparoscopy-related complications such as bile duct injury (including biloma, bile peritonitis, sepsis, multiple organ dysfunction syndrome, external biliary fistula, cholangitis, liver abscess, and others) are often associated with concomitant vascular injury [16; 17] or even haemobilia, in some rare cases [18]. We discovered that the intermediate cholecystectomy group was associated with significantly fewer complications than the early cholecystectomy group. In the 1998-2013 subgroup, both the intermediate and delayed cholecystectomy groups had lower complication rates than the early cholecystectomy group; this reveals that there was a greater improvement in the 2013-2015 subgroup, which is consistent with the evidence from the 2013 Tokyo guidelines, which had previously given suggestions regarding the severity assessment of acute cholecitis patients with or without cholangitis. We also noticed that after analyzing the group of intermediate cholecystectomy patients in the original data from 1998-2015, the recurrence rates and mortality rates in the 1998-2013 subgroup and in the 2014-2015 group were found to be statistically insignificant compared to the early cholecystectomy group. However, a lower complication rate was found in the cohort compared to the early cholecystectomy group in the original data from 1998-2015 (aHR 0.296, 95% CI 0.275-0.318, \(p\leq 0.001\)) and the 1998-2013 subgroup (aHR 0.305, 95% CI 0.281-0.330, \(p\leq 0.001\)), and the same phenomenon was found to be even more pronounced in the 2014-2015 subgroup (aHR 0.243, 95% CI 0.202-0.293, \(p\leq 0.001\)). Aspects of the analysis of the delayed cholecystectomy group revealed that, in the raw data from 1998-2015 (aHR 1.704, 95% CI 1.498-1.939, \(p\leq 0.001\)) and in the 1998-2013 subgroup (aHR 1.769, 95% CI 1.540-2.031, \(p\leq\)0.001), the recurrence rate was higher compared to the early cholecystectomy group. However, according to the cut-off year when the 2013 Tokyo guidelines were published, no significant difference in the recurrence rates was found for the delayed cholecystectomy group after 2014-2015 (aHR 1.024, 95% CI 0.717-1.461, \(p=0.897\)). A higher mortality rate of the patients who had a delayed cholecystectomy was found in the raw data from 1998-2015 (aHR 1.511, 95% CI 1.313-1.739, \(p\leq 0.001\)) and in the 1998-2013 subgroup (aHR 1.508, 95% CI 1.304-1.743, \(p\leq 0.001\)) compared to the patients who had an early cholecystectomy. No significant difference in the mortality rates was found for the delayed cholecystectomy group after 2014-2015 (aHR 1.209, 95% CI 0.668-2.187, \(p=0.531\)). Nevertheless, a lower complication rate was also found in the cohort compared to the early cholecystectomy group in the original data from 1998-2015, the 1998-2013 subgroup, and the 2014-2015 subgroup. This could be due to a variety of factors. First, the recurrence rates may have decreased as a result of increased surgical expertise, the improvements in the quality of ERCP, as well as various endoscopic techniques [8]. Therefore, we can see that both of the intermediate cholecystectomy and delayed cholecystectomy groups showed decreasing trends in the recurrence rates.