[1] Sungkyunkwan Univ, Sch Med, Samsung Med Ctr, Dept Surg, 81 Irwon Ro, Seoul 06351, South Korea
[2] Sungkyunkwan Univ, Sch Med, Samsung Med Ctr, Dept Anesthesiol & Pain Med, Seoul, South Korea
[3] Samsung Med Ctr, Stat & Data Ctr, Seoul, South Korea
[4] Sungkyunkwan Univ, Sch Med, Samsung Med Ctr, Dept Med, Seoul, South Korea
[5] Univ N Carolina, Dept Surg, Chapel Hill, NC 27515 USA
[6] Tokyo Womens Med Univ, Inst Gastroenterol, Dept Surg, Tokyo, Japan