External validation of the Japanese difficulty score for laparoscopic hepatectomy in patients undergoing robotic-assisted hepatectomy.

Introduction: The Japanese difficulty score (JDS) categorizes laparoscopic hepatectomy into low, intermediate, and high complexity procedures, and correlates with operative and postoperative outcomes. We sought to perform a validation study to determine if the JDS correlates with operative and postoperative indicators of surgical complexity for patients undergoing robotic-assisted hepatectomy.

Methods: Retrospective review of 657 minimally invasive hepatectomy procedures was performed between January 2008 through March 2019. Outcomes included operative time, estimated blood loss (EBL), blood transfusion, complications, post-hepatectomy liver failure (PHLF), length of stay, 30-day readmission, and 30-day and 90-day mortality. Patients were grouped based on JDS defined as: low (< 4), intermediate (4-6), and high (7 +) complexity procedures. Statistical comparisons were analyzed by ANOVA or χ test.

Results: 241 of 657 patients underwent robotic-assisted resection. Of these patients, 137 were included in the analysis based on JDS: 25 low, 58 intermediate, and 54 high. High JDS was associated with more major resections (≥ 4 contiguous segments) versus minor resections (median JDS 8 vs. 5, P < 0.0001). High JDS was associated with significantly longer operative times, higher EBL, and more blood transfusions. High JDS was associated with higher rates of PHLF at 16.7%, compared with 5.2% intermediate and 0.0% low, (P = 0.018). Complication rates, 30-day readmissions, and mortality rates were similar between groups. Median LOS was longer in patients with high JDS compared with intermediate and low (4 days vs. 3 days vs. 2 days; P = 0.0005).

Discussion: Higher JDS was associated with multiple indicators of operative complexity, including greater extent of resection, increased operative time, EBL, blood transfusion, PHLF, and LOS. This validation study supports the ability of the JDS to categorize patients undergoing robotic-assisted hepatectomy by complexity.