[1] San Francisco VA Med Ctr, Div Nephrol, Dept Med, San Francisco, CA 94121 USA
[2] Univ Calif San Francisco, Dept Med, San Francisco, CA USA
[3] Northwestern Univ, Sch Med, Div Gen Internal Med, Chicago, IL USA
[4] Washington DC VA Med Ctr, Surg Serv, Washington, DC USA
[5] George Washington Univ, Dept Surg, Washington, DC USA
[6] Georgetown Univ, Dept Surg, Washington, DC USA
[7] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA
[8] San Francisco Gen Hosp, Dept Med, San Francisco, CA 94110 USA
[9] Tenet Hlth Syst, Med Affairs, Clin Effectiveness, Dallas, TX USA
[10] Harvard Univ, Sch Med, Dept Med, Boston, MA USA
[11] Harvard Univ, Sch Med, Dept Surg, Boston, MA USA
[12] VA Boston Healthcare Syst, Surg Serv, Boston, MA USA
[13] Univ Colorado, Hlth Outcomes Program, Denver, CO 80202 USA