1. Center of Residency and Fellowship Program, Faculty of Medicine, University Hospital of the Ryukyus, Uehara, Nishihara, Okinawa, Japan
2. Dialysis Unit, University Hospital of the Ryukyus, Uehara, Nishihara, Okinawa, Japan
3. Okinawa General Health Maintenance Association, Miyahira, Haebaru, Okinawa, Japan