Michael Froehner1, Rainer Koch2, Manfred P Wirth3. 1. Department of Urology, University Hospital "Carl Gustav Carus," Technische Universität Dresden, Dresden, Germany. Electronic address: Michael.Froehner@uniklinikum-dresden.de. 2. Department of Medical Statistics and Biometry, University Hospital "Carl Gustav Carus," Technische Universität Dresden, Dresden, Germany. 3. Department of Urology, University Hospital "Carl Gustav Carus," Technische Universität Dresden, Dresden, Germany.