1. Laboratory of Veterinary Surgery, Hokkaido University, Sapporo, Hokkaido 060–0818, Japan
2. *Laboratory of Comparative Pathology, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060–0818, Japan
3. †Makoto Animal Hospital, Asahi Building, 2‐2, Kitago, Shiroishi‐ku, Sapporo, Hokkaido 003–0832, Japan