1. Department of Colorectal Surgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
2. Department of Ultrasonography, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
3. Department of Anorectal Surgery, The Third People's Hospital of Hangzhou, Hangzhou, Zhejiang, China
4. Department of Colorectal Surgery, The First People's Hospital of Yuhang District, Hangzhou, Zhejiang, China