Capital Medical University, Capital Medical University, Capital Medical University - Department of Gastrointestinal Surgery, Capital Medical University, Capital Medical University, Capital Medical University, Capital Medical University, Capital Medical University, Capital Medical University, Capital Medical University, affiliation not provided to SSRN, Capital Medical University - Department of Gastrointestinal Surgery, Capital Medical University - Department of Gastrointestinal Surgery, University of Georgia - Department of Epidemiology and Biostatistics, Capital Medical University and Capital Medical University - Department of Gastrointestinal Surgery