1. Department of Gastroenterology Daping Hospital Army Medical University Chongqing 400032 P. R. China
2. State Key Laboratory of Cancer Biology Department of Medical Genetics and Development Biology Fourth Military Medical University Xi'an 710032 P. R. China
3. Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology School of Chemistry and Chemical Engineering Northwestern Polytechnical University Xi'an 710072 P. R. China
4. Xi'an People's Hospital (Xi'an Fouth Hospital) Shaanxi Eye Hospital Affiliated Guangren Hospital School of Medicine Xi'an Jiaotong University Xi'an 710004 P. R. China
5. Department of General Surgery Tangdu Hospital Fourth Military Medical University Xi'an 710038 P. R. China
6. Department of Surgery Tangdu Hospital Fourth Military Medical University Xi'an 710038 P. R. China