[1] Univ Washington, Dept Surg, Surg Outcomes Res Ctr, UW Med Ctr, Box 354808,1107 NE 45th St,Suite 502, Seattle, WA 98105 USA
[2] Univ Michigan, Dept Surg, Ann Arbor, MI 48109 USA
[3] Univ Washington, Dept Urol, Seattle, WA 98195 USA
[4] Black Hills Ctr Amer Indian Hlth, Rapid City, SD USA
[5] Univ Washington, Dept Epidemiol, Seattle, WA 98195 USA