[1] Mayo Clin & Mayo Fdn, Mayo Med Sch, Div Colon & Rectal Surg, Rochester, MN 55905 USA
[2] Lahey Clin Fdn, Dept Colon & Rectal Surg, Boston, MA USA
[3] Tufts Univ, Sch Med, Boston, MA 02111 USA
[4] Univ Minnesota, Div Colon & Rectal Surg, Minneapolis, MN USA