BackgroundMinimally-invasive hepatectomy (MIH) is increasingly utilized; however, predictors and outcomes for patients requiring conversion to an open procedure have not been adequately studied. MethodsThe 2014–15 ACS-NSQIP database was analyzed. Unplanned conversion was compared to successful MIH and elective open hepatectomy. ResultsAmong 6918 hepatectomies, 1062 (15.4%) underwent attempted MIH: 989 laparoscopic, 73 robotic. Conversion occurred in 203 (19.1%). Compared to successful MIH, patients requiring unplanned conversion experienced higher rates of complications (34.5% vs 14.6%, p<0.001), including bile leaks (7.4% vs 2.8%, p=0.002), organ space infection (6.4% vs 2.9%, p=0.016), UTI (4.9% vs 1.2%, p=0.002), perioperative bleeding (21.2% vs 6.1%, p<0.001), DVT (3.0% vs 0.8%, p=0.024), and sepsis (5.9% vs 1.9%, p=0.001). Conversion led to greater LOS (5 days vs 3 days, p<0.001) and 30-day mortality (3.0% vs 0.5%, p=0.005). Compared to elective open hepatectomy, conversion was associated with greater perioperative bleeding (21.2% vs 15.3%, p = 0.037). On multivariate analysis, major hepatectomy (OR 2.21, p<0.001), concurrent ablation (OR 1.79, p=0.020), and laparoscopic approach (vs. robotic) (OR 3.22, p=0.014) were associated with conversion. ConclusionAnalysis of this national database revealed unplanned conversion during MIH is associated with greater morbidity and mortality. MIH should be approached cautiously in patients requiring major hepatectomy.