This is a retrospective cohort study of robotic liver resection (RLR) using the SynchroSeal energy device performed at two high volume hepatobiliary centres. All consecutive patients undergoing robotic liver resection at the Amsterdam UMC and Groeninge Hospital in Kortrijk who underwent robotic liver resection whereby the SynchroSeal or Vessel Sealer device were utilized during parenchymal transection were included. Liver transplant hepatectomies, cyst fenestrations, biopsies and emergency procedures were excluded. The first 25 procedures performed with the Vessel Sealer per center were excluded to correct for effect of the initial robotic learning curve [13]. Results of robotic liver resections using the SynchroSeal were compared to those using the Vessel Sealer. The study is reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement [14].

Procedures performed with the SynchroSeal and Vessel Sealer were identified from the Amsterdam UMC MILS Registry and a local MILS database of AZ Groeninge. The databases are prospectively maintained and contain data on patient, disease and procedure characteristics along with peri- and postoperative outcomes. The following patient characteristics were collected: age at time of operation, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, use of neoadjuvant chemotherapy, presence of Cirrhosis, previous abdominal surgery and previous liver surgery. Disease characteristics of interest were histopathological diagnosis, largest tumour size, number of lesions on CT and presence of bilobar disease. Procedure characteristics included year of operation, type of hepatectomy (minor, technically major, anatomically major), extent of resection (wedge, segmentectomy, bi-segmentectomy, tri-segmentectomy, (extended) left/right hemi-hepatectomy), concurrent ablation, and concurrent operation (excluding cholecystectomy and lymphadenectomy). Intraoperative outcomes were operation duration, estimated intraoperative blood loss, major blood loss, use and duration of the Pringle manoeuvre, rate of conversion to open surgery and use of intraoperative transfusion. Postoperative outcomes were postoperative length of hospital-stay, Intensive Care Unit (ICU) admission, morbidity, severe morbidity, bile leak, readmission, reintervention, reoperation, 30-day or in-hospital mortality, resection margin status and textbook outcome in liver surgery (TOLS). Outcomes were reported with a follow-up of thirty days.

Liver segments are classified according to the Couinaud classification [15]. Patients were classified into three groups, minor, technically major and anatomically major, according to the extent and location of the resection performed. Minor resections were defined as resections of segments 2, 3, 4b, 5 or 6, involving less than three adjacent liver segments. Technically major resections are resections of segments 1, 4a, 7 or 8 involving less than three adjacent liver segments. Anatomically major resections refer to resections involving three or more adjacent liver segments. Intraoperative incidents were graded according to the Oslo classification [16]. The presence of cirrhosis was defined based on pathologic examination of the liver parenchyma. Operation duration was defined as the time in between the start of the skin incision until wound closure. Intraoperative blood loss was calculated by subtracting the volume of irrigation fluid from the volume of aspirated blood and blood absorbed by gauzes. Major blood loss was defined as intraoperative blood loss of 500 mL or more. Radical resection (R0) was characterized as histological evidence of tumour-free margins and at least 1 mm from the resection surface. Postoperative hospital length of stay is the number of nights the patient was admitted following the operation. Morbidity was graded according to the Clavien-Dindo classification [17]. With severe complications defined as Clavien-Dindo grade IIIa and above. Bile leaks were classified according to the standardized classification by the International Study Group of Liver Surgery (ISGLS) [18]. TOLS was defined using the same parameters as in the consensus definition, though limited to 30-days follow-up due to the available data [19]. To achieve TOLS all the following parameters must be met; absence of intraoperative incidents (grade ≥ 2), postoperative bile leakage (ISGLS grade B/C), postoperative liver failure (grade B/C), 30-day severe postoperative complications, 30-day readmission, 30-day or in-hospital mortality and the presence of R0 resection margin. Additionally, the extended definition of TOLS was used (TOLS +), this involves all the previously listed parameters as well as the absence of prolonged postoperative length of stay. Prolonged length of stay was defined as > 3 days, > 5 days and > 10 days for minor, technically major and anatomically major resections.

All surgeons had completed their learning curve for robotic liver surgery (> 25 procedures) prior to the introduction of the SynchroSeal at their respective centres [13]. Whereas the Vessel Sealer device was introduced at the time of implementation of robotic liver surgery at both centres. The operating teams consisted of at least one console surgeon and one bedside surgeon (surgeon, resident or fellow). The surgical technique was not altered throughout the study period. All procedures were completed using the DaVinci Xi platform (Intuitive Surgical, Inc., Sunnyvale, CA). Trocar placement was dependent on resection size and location as depicted in Fig. 1. Intraoperative ultrasound and indocyanine green (ICG) fluorescence imaging were used to demarcate the lesion(s), identify its relation to relevant anatomical structures and assess resection margins intraoperatively. The Pringle manoeuvre was applied when deemed necessary in periods of up to 20 min followed by a 5-min reperfusion period and repeated maximally three times. When applied, the Pringle manoeuvre was performed intracorporeally using the Huang Loop technique [20]. The energy device (SynchroSeal or Vessel Sealer) was placed in the third robotic arm and applied during at least part of the parenchymal transection. Vessels were ligated using titanium clips, Hem-O-Lok clips (Teleflex Inc., Morrisville, NC, USA) or staplers depending on size and anatomy. Use of haemostatic sealants and abdominal drains was left at the discretion of the operating surgeon. Autologous blood transfusion was only used at one of the institutions and only utilized for anatomically major resections or resections with a large transection plane. To ensure a hypovolemic state, the autologous blood was reinfused after parenchymal transection. Enhanced Recovery After Surgery (ERAS) protocols were in effect at both institutions.

Port placement per hepatectomy type. Partial anterolateral resection (A), partial posterosuperior resection (B), left hemihepatectomy (C), and right hemihepatectomy (D). *Planned site of specimen extraction, location may differ depending on method of extraction. The second assistant port is optional and is primarily used in larger resections.

Ethical approval for the use of patient data for the study was obtained from the medical ethics committee of the Amsterdam UMC (2023.0279) and AZ Groeninge Hospital (AZGS2023028) who waived the need for informed consent. The study was performed in accordance with the ethical principles outlined in the Declaration of Helsinki.

Continuous variables are expressed as means with standard deviation (SD) if normally distributed or as medians with interquartile range (IQR) in the case of non-parametric data. Categorical data is displayed as absolute numbers with percentages. Comparisons of continuous data were made using the independent samples t-test if normally distributed and Mann–Whitney U when non-normally distributed. Comparisons of categorical data were made using the chi-squared test or Fisher’s exact test when appropriate. Propensity score matching was employed to mitigate selection bias, utilizing a 1:1 nearest neighbour matching approach with a caliper width set at 0.1. The groups were matched for the following variables: age, BMI, sex, ASA grade, presence of cirrhosis, neoadjuvant chemo, history of extrahepatic abdominal surgery, history of liver surgery, pathological diagnosis, largest lesion size, number of lesions, presence of bilobar disease, type of resection, resection difficulty (minor, technically major, anatomically major) concurrent ablation and concurrent operation. Missing data regarding ASA grade (n = 4, 1.3%) and size of largest lesion (n = 13; 4.3%) were imputed by means of single imputation. Paired t-test and Wilcoxon signed-rank test were utilized to compare the matched groups for continuous and categorical data respectively. All analyses were performed using IBM SPSS Statistics for Windows version 26.0 (SPSS V26.0, Inc., Chicago, IL, USA) and R for Windows version 4.3.2 (R Foundation for Statistical Computing, Vienna, Austria).