Dilation of the Cystic Duct Confluence in Laparoscopic Common Bile Duct Exploration and stone extraction for Patients with Secondary Choledocholithiasis

Objectives : Many options exist in the management of cholelithiasis and secondary choledocholithiasis. Among them, laparoscopic common bile duct exploration (LCBDE) with the choledocotomy followed by laparoscopic cholecystectomy has gained popularity. However, efforts should be made for minimally invasive or non-invasive to the common bile duct (CBD). For this purpose, we modified the surgical modality of laparoscopic transcystic approach by dilating the cystic duct confluence in CBD exploration (LTD-CBDE). Based on our preliminary experience, the aim of this work was to assess the feasibility, safety and effectivity of LTD-CBDE. Patients and methods : Sixty-eight patients were arbitrarily offered new LTD-CBDE technique from December 2015 to April 2018. During the surgery, we dilated the cystic duct confluence with separation forceps and/or the columnar dilation balloon. Subsequently, the CBD exploration and stone extraction were performed with choledochoscope. The entrance of CBD was covered with cystic duct stump wall and primarily closed at the end of surgery. Results : 49 females and 19 males with cholelithiasis and secondary choledocholithiasis were included. The mean age was 53 years old (18 to 72 yr). Of which, 62 cases (91.2%) were performed with LTD-CBDE techniques successfully, bile leakage was observed in 3 cases (4.4%). The mean operation time was 106 minutes and the mean hospital stay was 5.9 days. As for the other 6 patients, 3 cases were converted to open cholecystectomy due to severe fibrosis, unclear anatomical structure at the Calot’s triangle (n=2) and Mirizze syndrome (n=1); LCBDE were performed in 3 patients due to cystic duct atresia (n=2) and low level of the gallbladder duct into CBD (n=1). These patients had smooth postoperative course. None of the patients presented radiological evidence of retained CBD stone on the postoperative follow-up in 43/68 (40 cases used LTD-CBDE) patients one year later. Conclusion : The current work suggests that LTD-CBDE


Introduction
The incidence of common bile duct (CBD) stones reported in the literature in patients with gall bladder stones varies between 7% and 20% [1][2][3] . Shortly after Bobbs performed the first cholecystectomy in 1867, Abbe performed the first CBD exploration [4] . Subsequently, open cholecystectomy and CBD exploration followed by T-tube drainage gradually became a classic surgical modality for patients with cholelithiasis and secondary choledocholithiasis. With the introduction of endoscopy and laparoscopy into clinic in the 1970s and 1980s, as also accompanied by the evolution of widespread expertise, laparoscopic cholecystectomy (LC) has been rapidly accepted as a routine treatment for patients with symptomatic gall bladder stones, and has also gradually as the conventional management of CBD stone [5] . In China, Yunnan Province is a highprevalence area of lithiasis. A hospital in Qujing city introduced laparoscopic techniques to China first in 1991, and more than 100 cases of LC were performed that year.
Compared with ERCP followed by LC, LCBDE has the advantage of a higher success rate and a shorter hospital stay while simplifying the two procedures into a single minimally invasive operation [5] .
However, in most cases, the LCBDE modality usually has to be performed via a choledochotomy followed by T-tube drainage. T-tube placement presents difficulties in post-operative management [12] . Thus, Chen et al. [13] and Niu et al. [14] modified transcystic approach with micro-incision of the cystic duct confluence or CBD followed by primary suture without a T-tube. Results had achieved good preliminary effects. Despite this, we think that micro-incision is still a kind of injury to CBD, and in the long run, patients might suffer from CBD stenosis, especially for those patients with CBD stenosis before operation. Therefore, efforts should be made to minimize the injury to the cystic duct confluence or CBD, preferably "no injury". For this purpose, we modified the surgical modality by replacing choledochotomy or confluence incision with Laparoscopic Transcystic Dilation of the cystic duct confluence in CBDExploration (LTD-CBDE). The basic idea is that since secondary CBD stone originates from gall bladder stone and in some cases the stones will fall through the cystic duct into the CBD, indicating that if the natural cystic duct and the cystic duct confluence can be safely dilated, possibly the stones will be found and removed through choledochoscope. The improved procedure takes full advantage of the natural tube of the cystic duct and avoids incision CBD. In this article, we report our preliminary experience during the last three years, and assess the feasibility, safety and effectivity of LTD-CBDE technique.

Patients And Methods
This study was approved by the Institutional Review Board of The Qujing First People's Hospital, and was considered not requiring informed consent given the retrospective nature of using patients' data. Meanwhile, the outer diameter, location and size of the CBD stones were also clearly defined and recorded. The patients presented with acute cholangitis and acute gallbladder pancreatitis were excluded from undergoing LTD-CBDE. All patients underwent routine preoperative examination, including chest X-ray, electrocardiogram, routine blood test, liver and kidney function testing, and coagulation function testing. All patients were informed about both the procedures and the technologies possibly being selected and provided written informed consent.
Operations were performed by the same surgical team under general anesthesia and endotracheal intubation. During the operation, the patients were placed in reverse trendelenburg positions, tilting to the left. Pneumoperitoneum was established with carbon dioxide at a pressure of 12-15 mmHg and adjusted as needed. Four trocars were used for LC according to the standard technique. The detailed surgery flow diagram is shown in figure 1. The Calot's triangle was dissected, and the cystic artery, cystic duct and CBD were exposed. The cystic artery was clipped and ligated first. Then, the cystic duct was clipped highly near the GB, and 3/4 of its cross section was cut open approximately 0.5cm from the CBD. The choledochoscope (4.9 mm, Olympus, Tokyo, Japan) was inserted through the cystic duct and confluence for the CBD exploration and stone extraction (success in 9 cases). Stones were removed with a Cook basket (NTSE-045065-UDH). If failed, one of next steps were performed: (i) LCBDE modality (n=114); or (ii) the ventral side of the cystic duct was longitudinally incised 0.2-0.3 cm from the above-mentioned incision of cross section, and the confluence was dilated through cystic duct with the separation forceps (figure 2), and then the choledochoscope was inserted again; or (iii) columnar dilation balloon (M00558410) was used to dilate the confluence (figure 3) until the choledochoscope was successfully inserted followed by the CBD exploration and stone extraction. The choledochoscope was also turned upward to explore the common hepatic duct and intrahepatic ducts.
If intrahepatic ducts present no stones, then the distal CBD was explored again. Intraoperatively, the 68 patients reported herein (red dotted box in figure 1) were selected arbitrarily to adopt the surgical methods (LTD-CBDE modality) described in (ii) and (iii) above. As far as our practical experience was concerned, the dilation degree of the cystic duct and/or the confluence depended on the size of the largest stone individually, which was determined basing on preoperative US or MRCP examination.
After the stones were removed totally (the CBD was completely clear and no evidence of remnant stones), the cystic duct was cut and LC was performed. The stump wall of the cystic duct was used to cover the entrance of CBD, primarily by laparoscopic interrupted full-thickness suturing, as shown in Data are presented with numbers, percentage, arithmetic mean ± standard deviation (SD).

Results
Sixty-eight patients with cholelithiasis and secondary choledocholithiasis were arbitrarily offered LTD-CBDE. Table 1

Discussion
The secondary CBD stone may cause many clinical symptoms and signs, including abdominal pain, obstructive jaundice, cholangitis, and biliary pancreatitis, etc [2] . Like patients in this article, there were as many as 52 patients diagnosed as obstructive jaundice. The ideal management remains a matter of debate [5] . As far as LCBDE is concerned, the problems are mainly related to T-tube placement, such as patient discomfort, biliary peritonitis, T-tube displacement, etc [15][16] . In view of this, some surgeons tried to make full use of the natural cystic duct with micro-incision on CBD or confluence followed by primarily suture [13][14] . Inspired by this, we further speculate: could we use the natural orifices comprising of cystic duct and its confluence at the CBD with no incision? Therefore, LTD-CBDE was designed for CBD exploration and stones extraction via laparoscopic transcystic approach by dilating the confluence. Dilation of the confluence making the insertion of the choledochoscope and stones extraction easier, because is it not only overcomes the problems that the cystic duct is thin and the spiral valve acts as a barrier in exploration, but also enlarges the inlet diameter of the CBD greater or equal to the outer diameter of the largest stone. CBD blood supply is not affected by incision so that CBD stenosis may be prevented. The operations were performed smoothly. Success rate was 91.2% (may be higher with careful perioperative identification of the indications), clearance rate of CBDS was 100%, and retained stones were not identified on postoperative follow-up.
The success rate of 91.2% with present method coincides with 88.1% reported in meta-analysis of eleven randomized trials for LCBDE [5] . By using a slightly different approach with a micro-incision at the confluence, Chen et al. and Niu et al reported a success rate of 100% [13][14] . The 6 failed patients in our work were associated with anatomical problems, suggesting the importance of a carefully selected surgical strategy. Special attention should be paid to the following aspects: Firstly, it is crucial to maintain the cystic duct intact, so as to facilitate the incision, dilation, choledochoscope insertion, observation, stones extraction and primary closure. Secondly, identify the confluence correctly and avoid its damage. Finally, limiting factors of success with LTD-CBDE include anatomic features related to the cystic duct and confluence, such as fibrosis and anatomical abnormality of the Calot's triangle, small-size or atretic or tortuous duct, and low level of or posterior insertion of the cystic duct on the CBD, etc.
The operation time reported in the literatures varies widely depending on the surgical method, ranging from 104 to 194 minutes [2,13,17,18] . The mean operating time was 105 minutes in our series. However, we don't think it is reasonable to directly compare the operation time, because any new modality requires more operation time, and is technically difficult with a clear learning curve. In the future, along with technical improvement and more effective logistic organization, the operation time will be further reduced. Patients in our study were discharged after a mean postoperative hospital stay of 5.9 days, which is not longer than other reports with mini-incision (mean 8 days) or LCBDE [5,17,18] . Mortality is also in accordance with the findings of other surgical modality [13][14] .
Forty-three cases were followed up one year after LTD-CBDE operation (25 patients lost to follow up) and none of them presented with evidence of retained or recurrent CBDS and stenosis of CBD.
Our LTD-CBDE is safe and effective, but a carefully selected surgical strategy should be especially emphasized as suggested by Gigot et al. [18] . Firstly, for patients with anatomical abnormalities or intraperitoneal adhesions as 6 patients shown in our series, the traditional open operation or laparoscopic choledochotomy should be considered as soon as possible. Secondly, despite careful suturing of the confluence with stump wall, there were still 3 cases suffering postoperative bile leakage. This is not higher than the incidence of LCBDE (5.6% with experienced surgeons vs 17.1% with inexperienced surgeons) reported by liu et al. [19] . As analyzed by liu. et al. [19] , it is clear that postoperative bile leakage (and the like) can be reduced with gaining of experience in the technique Anesthesiologists physical status; CBD: common bile duct. Values are expressed as mean ± SD or number of patients (%); MRCP: magnetic resonance cholangiopancreatography. Values are expressed as number of patients (%). Figure 1 The  The confluence was dilated with the separation forceps (red arrow) Figure 3 The confluence was dilated with the columnar dilation balloon (red arrow)

Figure 4
The stump wall of the cystic duct covers the entrance of CBD followed by primarily close.

Supplementary Files
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