1. Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-0054, Japan
2. Animal Clinical Research Foundation, 214-10 Yatsuya, Kurayoshi, Tottori 682-0025, Japan
3. First Department of Surgery, Faculty of Medicine, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-0004, Japan