The da Vinci Single-Site™ Instrumentation and the da Vinci® Si™ System (Intuitive Surgical®, Sunnyvale, CA, USA) was adopted for RSSC. A single-site port was used for RSSC that included five lumens consisting of an 8.5-mm endoscope, a 5-mm or 10-mm accessory port, a curved cannula, and an insufflation adaptor. Additionally, a curved 5-mm instrument cannula designed for optimizing triangulation toward the operative field and several 5-mm semi-rigid instruments were employed for the operative procedure (Fig. 1).

The robot single-site surgical system was applied to RSSC with a specialized single port for robotic surgery and a curved cannula with flexible instruments. A vertical 2-cm transumbilical skin incision was made, and the fascia layer was opened in same direction. After the single port consisting of a pliable silicone architecture was inserted into the fascial opening using Kelly forceps and an Army retractor, a pneumoperitoneum was created by carbon dioxide gas inflation. A camera was inserted to explore the peritoneal cavity and localize the fundus of the gallbladder after inserting the 8.5-mm camera port. The patient table was rotated to align with the orientation of the umbilicus to the fundus of the gallbladder (main axis). The patient-side cart of the robotic surgical system was moved to the patient table along the main axis. The robotic arm was docked to the camera port, curved cannula, and accessory trocar, according to predetermined sequences.7 Flexible robotic instruments were inserted through the curved cannula, and the robotic system provided a switching motion between right-hand and left-hand orientations to improve the surgeon's ergonomics. The assistant surgeon performed gallbladder traction toward the lateral and upward direction to expose Calot's triangle. After dissecting around the GB neck and cystic duct, the cystic duct and cystic artery were ligated securely by intracorporeal tie ligation and a Hem-o-lok clip and then divided with robotic scissors. Compared to laparoscopic single-port surgery, the robotic single-port surgical system provided a stable environment to perform intracorporeal tie ligation, despite the absence of EndoWrist movement. Additionally, the robotic single-port surgical system has a special feature, called Intraoperative Firefly™ Fluorescence Imaging. This feature allows the surgeon to visualize the biliary system during the operation by intravenous injection of ICG before the operation and a NIR light for real-time fluorescent cholangiography (Fig. 2, Supplementary Video 1). After dividing the cystic duct and the cystic artery, the gallbladder was dissected meticulously from the liver bed to prevent perforation of the gallbladder and spillage of bile into the peritoneal cavity. An Endo-pouch was inserted into the operative field via an accessory trocar, which was handled by the assistant surgeon. The specimen was retrieved using the Endo-pouch and delivered through the transumbilical incision. The fascia and skin were closed layer by layer.

To compare the improvement of proficiency and learning period for early experiences of the new surgical technique, the first 20 cases that received a single-fulcrum laparoscopic cholecystectomy (SFLC) were obtained in our prospective data set.10,11 We compared factors including clinicopathologic factors and operative outcomes between RSSC and SFLC. The total operation time was defined as the length of time from the beginning of the skin incision to the final closure of the wound. The actual dissection time included the period from the dissection of Calot's triangle to the retrieval of the specimen.

Continuous variables are expressed as the mean±the standard deviation and categorical variables are shown as frequencies and percentages. The Mann-Whitney U test for continuous variables and the chi-square test were employed to explore statistically significant associations between parameters. Statistical significance was determined if the p-value was less than 0.05.

RSSC was performed consecutively in 5 patients by a single surgeon between October 2013 and November 2013. Four patients were females and one was male; the median age of the patients was 35 years old (range: 29-53) (Table 1). Despite strict selection criteria for patient enrollments, we observed moderate inflammatory changes around the Calot area and dilated cystic duct requiring intracorporeal tie ligation before endoscopic clipping in most cases. Additionally, the surgical system induced an upward medial retraction of the GB by the assisting surgeon, which caused a narrowing of Calot's triangle, leading to prolonged dissection time, in contrast to SFLC (Table 2). Neither bile duct injury nor bile spillage occurred during any of the operations. Robotic setting (docking) time, actual dissection time, and intraoperative blood loss seemed to decrease gradually as case numbers increased (Fig. 3). There were no open conversion cases, and most of the patients were discharged the day after the operation.

We compared the perioperative outcomes of RSSC (n=5) with the first 20 outcomes of SFLC (n=20) in order to evaluate the technical validation of the robotic single-site surgical system when applied to laparoscopic cholecystectomy (Table 2). Based on previous analysis of the learning curve for SFLC,11 we obtained 20 initial cases as the training phase in the database for SFLC. In comparisons between RSSC and SFLC groups, there were no statistically significant differences in most patient-related factors, such as age, sex, Body Mass Index, diagnosis, and American Society of Anesthesiologist score (p>0.05). The operative outcomes regarding intraoperative blood loss, bile spillage during operation, postoperative pain scale values, postoperative complications, and length of hospital stay did not show significant differences between the two groups (p>0.05). However, there were significant differences in operative time (RSSC: 132.6±25.2 min; SFLC: 39.75±15.6 min; p=0.001) and actual dissection time (RSSC: 53.4±8.4 min; SFLC: 32.2±13.4 min; p=0.003) between the two groups.