1. Department of Colorectal Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan
2. Graduate Institute of Clinical Medical Science, College of Medicine, Chang Gung University, Kaohsiung 333, Taiwan
3. Department of Surgery, University of California, San Diego Health System, La Jolla, CA 92103, USA
4. Rebecca and John Moores Cancer Center, University of California, San Diego Health System, La Jolla, CA 92103, USA