[1] Ajou Univ, Sch Med, Dept Pediat, Suwon 441749, South Korea
[2] Southmead Hosp, Childrens & Acad Renal Unit, Bristol, Avon, England
[3] Chungbuk Natl Univ, Coll Med, Dept Pediat, Cheongju, South Korea
[4] Yonsei Univ, Coll Med, Dept Pediat, Seoul, South Korea