Relationship between hospital volume and operative mortality for liver resection: Data from the Japanese Diagnosis Procedure Combination database

Aim: The present study aimed to conduct a nationwide investigation on the relationship between hospital volume and outcomes following liver resection in Japan. We also discuss health policy implications of the results. Methods: Using the Japanese Diagnosis Procedure Combination database, we identified 18 046 patients who underwent hepatic resection between July and December 20072009. Patients were subdivided into hospital-volume quartiles: very low- (<18/year), low- (1835), high- (3670) and very high-volume groups (>70). Multivariate logistic regression analysis for in-hospital mortality within 30 days of surgery was performed to analyze adjusted effects of various factors. Results: Patients in the very high-volume group had a higher Charlson Comorbidity Index (P < 0.001) than those in the very low-volume group. Very low-volume hospitals were significantly less likely to perform extended lobectomy than very high-volume hospitals (5.4% vs 17.6%, P < 0.001). Crude in-hospital mortality within 30 days of surgery was 1.1% (0.6%, 0.8%, 1.9% and 3.0% for limited resection, segmentectomy, lobectomy and extended lobectomy, respectively). With reference to the very low-volume group, risk-adjusted odds ratios (95% confidence intervals) of low-, high- and very high-volume groups for overall mortality were 0.70 (0.481.02; P = 0.060), 0.52 (0.340.81; P = 0.004) and 0.16 (0.090.30; P < 0.001), respectively. Conclusion: There is a linear trend between higher hospital volume and lower in-hospital mortality of liver resection in Japan, particularly for lobectomy and extended lobectomy. Based on these results, regionalization of lobectomy and extended lobectomy in high-volume centers could be effective for reducing postoperative mortality.