Navigation with laparoscopic ultrasound during fundus-rst laparoscopic cholecystectomy-a single-centre retrospective case control study


 Background

Laparoscopic cholecystectomy is considered as the gold standard treatment for cholecystolithiasis. The critical view of safety is a generally accepted technique of intraoperative visualization but during inflammation and fibrosis in the region of Calot’s triangle it may fail. Fundus-first laparoscopic cholecystectomy with laparoscopic ultrasound navigation may be an attractive bail-out option when the intraoperative conditions are difficult.
Methods

The study group consisted of 900 patients with symptomatic cholecystolithiasis which was divided into two subgroups. The first subgroup where the only method of intraoperative identification was the critical view of safety consisted of 402 patients, the second subgroup where the critical view of safety and laparoscopic ultrasound were used consisted of 498 patients. In the first subgroup fundus-first laparoscopic cholecystectomy was performed in 13 patients, in the second subgroup in 42 patients. Statistical analysis included the Mann-Whitney U test for continuous and Fisher’s exact test for binary variables. The level of statistical significance was set at 95% (p < 0.05).
Results

Fundus-first technique was significantly more often in the subgroup with laparoscopic ultrasound and the hospitalization time of fundus-first laparoscopic cholecystectomies was significantly shorter than in converted cases. The mean time of laparoscopic cholecystectomy and the mean time to obtain the transection level between the gallbladder and the hepatoduodenal ligament were significantly shorter and the conversion rate was significantly lower in the fundus-first and laparoscopic ultrasound group.
Conclusions

Fundus-first technique with laparoscopic ultrasound navigation may be a very efficient bail-out option during laparoscopic cholecystectomy due to a more precisely and significantly faster defined plane of dissection what enables safe performance of laparoscopic cholecystectomy with significantly lower rate of conversions.


Results
Fundus-rst technique was signi cantly more often in the subgroup with laparoscopic ultrasound and the hospitalization time of fundus-rst laparoscopic cholecystectomies was signi cantly shorter than in converted cases. The mean time of laparoscopic cholecystectomy and the mean time to obtain the transection level between the gallbladder and the hepatoduodenal ligament were signi cantly shorter and the conversion rate was signi cantly lower in the fundus-rst and laparoscopic ultrasound group.

Conclusions
Fundus-rst technique with laparoscopic ultrasound navigation may be a very e cient bail-out option during laparoscopic cholecystectomy due to a more precisely and signi cantly faster de ned plane of dissection what enables safe performance of laparoscopic cholecystectomy with signi cantly lower rate of conversions.

Background
Fundus-rst (FF) laparoscopic cholecystectomy (LC) is a technique which is used by some surgeons as a standard LC technique or, more often, as a bail-out procedure in case of a di cult LC [1][2][3][4][5]. Bile duct injury (BDI) or vasculobiliary injury (VBI) may be associated with the chronic in ammation in the region of Calot's triangle and di culties to de ne the safe plane of dissection during FF technique [2]. There are several visual landmarks like the Rouvier's sulcus, the base of liver segment IV or the sentinel node which may help to avoid BDI or VBI, but during preparation and in ammation the anatomical conditions are usually changed [6]. Intraoperative cholangiography (IOC) is an invasive procedure and cannulation of the cystic duct is not always possible due to brous obliteration of tissues [4]. The only method which in such situation may safely visualize both vascular and avascular structures and de ne the proper plane of dissection is laparoscopic ultrasound (LUS) [7]. LUS seems to be extremely useful during FF LC because the level of safe tissue transection may be very precisely de ned. Another goal of FF technique is the reduction of the conversion rate [5,8]. During FF dissection without LUS in case of in ammation and brosis in the region of the gallbladder's neck the conversion should not be delayed if at any point the anatomy is not clear [5,9]. With LUS the anatomy behind the visible plane of dissection is clearly de ned and the only factor which may disable safe FF LC are tissues laparoscopically undissectable.

Methods
The study group consisted of 900 patients operated on between January 2010 and February 2020 in one Department of Surgery. Inclusion criterion for the study was the symptomatic cholecystolithiasis. Exclusion criterion was the pre-or postoperatively diagnosed cancer of the gallbladder, preoperative acute cholecystitis and previous operations in the abdominal cavity. The study group was divided into two subgroups. The rst subgroup where the only method of intraoperative navigation was the critical view of safety (CVS) consisted of 402 patients (220 women and 182 men), the second subgroup where CVS and LUS were used consisted of 498 patients (277 women and 221 men). In the rst subgroup FF LC was performed in 13 patients (FF group), in the second subgroup in 42 patients (FF + LUS group). Written informed consent was obtained from all patients before surgery. All procedures were in accordance with the ethical standards of the 1964 Declaration of Helsinki and its later amendments and the study was approved by the Ethical Committee of the Wroclaw Medical University (approval number BW-24/2020).
Cholecystectomies were performed on an elective basis by three surgeons experienced in LC/open cholecystectomy (> 150 cholecystectomies) and LUS (> 70 examinations). For LUS were used the laparoscopic probe Toshiba PEF-704 LA (frequency 7.0-10 MHz) and the diagnostic ultrasound system Toshiba NemioMX SSA-590A all manufactured in Japan. LUS was performed in every patient from the second subgroup. Laparoscopic ultrasound probe was inserted through the epigastrical 10 mm (transverse view) or the umbilical 10 mm trocar (longitudinal view). Vascular and avascular structures were differentiated with power doppler function. The dissection started initially in the region of Calot's triangle and there was an attempt to reach the critical view of safety (CVS) but when the in ammatory plane was hard to prepare the FF technique was used ( Fig. 1) (Video 1). When the anatomy was unclear or the brous tissues were undissectable there was an attempt to perform subtotal cholecystectomy or the operation was converted. When there were problems with the traction during FF LC the liver was kept elevated by retractor. The key structure which was visualized throughout the procedure and de ned the proper plane of dissection during LUS was the "Mickey Mouse sign"-a characteristic con guration of the bile duct, the proper hepatic artery and the portal vein in the hepatoduodenal ligament which is similar to the head of Mickey Mouse (Fig. 2).
Statistical analysis included the Mann-Whitney U test for continuous and Fisher's exact test for binary variables.
The level of statistical signi cance was set at 95% (p < 0.05).

Results
The FF technique was signi cantly more often (p = 0.002) in the subgroup with LUS and the hospitalization time of FF LCs was signi cantly shorter than in converted cases. The mean time of LC and the mean time to obtain the transection level between the gallbladder and the hepatoduodenal ligament were signi cantly shorter and the conversion rate was signi cantly lower in the FF + LUS group (Tables 1 and 2). There were no signi cant differences between the two groups according to the age, the rate of bile duct injury and subtotal cholecystectomy (Tables 1 and 2). Two BDIs in the FF group were the leakages from the cystic stump (Strasberg A) after subtotal fenestrating cholecystectomy which were treated successfully with the endoscopic retrograde cholangiopancreatography. The reason for conversion in the FF + LUS group was the laparoscopically undissectable brous tissue which disabled safe performance of the procedure (3 patients) whereas in the FF group these were unclear anatomy (2 patients), undissectable brous tissue (2 patients) and bleeding (1 patient).   (3) presence of anatomical variations whereas the most common reason of BDI is the misidenti cation of the common hepatic/bile duct instead of the cystic duct [10,13,14]. The safest way to complete cholecystectomy is to obtain CVS but the problems may arise in the case of in ammation in the region of Calot's triangle [10,13,14]. CVS is not a dissection technique, but rather a technique of identi cation similar to the safety measures during hunting or ying [13,15]. There is no need to expose the common bile or hepatic duct while obtaining CVS [2]. CVS usually protects against incorrect identi cation but not against BDI and VBI during dissection when the local conditions are changed [15]. The possible bail-out techniques when CVS can not be reached include FF LC, subtotal LC, tube cholecystostomy or conversion [2,16].
FF LC is an alternative technique when there is a severe in ammation or brosis in the triangle of Calot [10].
During FF LC the gallbladder is dissected off the liver bed beginning with the fundus towards the infundibulum until it is hanging on the cystic duct and the cystic artery or it may be combined with the subtotal cholecystectomy [2]. The preferred dissection technique should be between the subserosal outer and inner layer of the gallbladder wall but in case of in ammation it may be very di cult [6]. The complications may involve haemorrhage from the liver bed or the gallbladder wall, migration of stones into the common bile duct or BDI/VBI associated with improper plane of dissection and higher rate of perforation of the gallbladder wall thus a stepby-step preparation and proper hemostasis are advised [2,3,5]. During standard technique the grasper on the fundus of the gallbladder is used to apply traction to expose the triangle of Calot [4]. When there are problems with the traction during FF the liver may be kept elevated by retractor [4]. LUS de nes very precisely the border between the gallbladder neck and common bile/hepatic duct enabling safe dissection plane. LUS is noninvasive, there is no need to cannulate the cystic duct and use the contrast dye. It is safe for both the patient and operating team and may be repeated as many times as it is needed [7]. IOC in case of advanced in ammatory changes usually fails [4,5].
FF technique leads to the reduction of conversion rate. The reported conversion rate for elective LC is 4-6% and for acute LC is 5-10% but recently the reported conversion rate was also very low at 0.04% [2,17]. Mangieri et al. Ethics approval and consent to participate Written informed consent was obtained from all patients before surgery and the study was approved by the Ethical Committee of the Wroclaw Medical University (approval number BW-24/2020).

Consent for publication
Written informed consent for publication was obtained from patients.

Availability of data and materials
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.