1. Mayo Clinic Alix School of Medicine, Scottsdale, AZ, USA
2. Department of Urology, Mayo Clinic, Mayo Clinic College of Medicine and Science, Scottsdale, AZ, USA
3. Department of Nephrology and Hypertension, Mayo Clinic, Scottsdale, AZ, USA
4. Department of Statistics, Mayo Clinic, Scottsdale, AZ, USA