Data collection
Data from our institution were preferentially considered compared to those from other institutions in order to eliminate selection bias in data from different hospitals. If patients who had been transferred were unable to undergo examination at our institution owing to their critical condition, data collected at other institutions were used. Perioperative data of all patients, including general characteristics, disease history, comorbidities, physical examination findings, laboratory test results, imaging data, and outcomes, were collected, entered by specialists, and reviewed by experienced and senior doctors.