[1] Univ Minnesota, Dept Surg, Med Sch, Box 242 UMHC, Minneapolis, MN 55455 USA
[2] Univ Minnesota, Sch Publ Hlth, Div Biostat, Minneapolis, MN 55455 USA
[3] Hosp Univ Penn, Dept Surg, Perelman Sch Med, 3400 Spruce St, Philadelphia, PA 19104 USA
[4] Univ Minnesota, Dept Med, Med Sch, Div Gastroenterol, Box 736 UMHC, Minneapolis, MN 55455 USA
[5] Univ Minnesota, Dept Pediat, Med Sch, Minneapolis, MN 55455 USA
[6] Univ Minnesota, Med Sch, Schulze Diabet Inst, Minneapolis, MN USA