1 Department of Urology, University Medical Center Utrecht, Utrecht, The Netherlands.
2 Department of Gastroenterology and Hepatology, University Medical Center Utrecht, PO BOX 85500, 3508 GA Utrecht, The Netherlands.
3 Department of Urology, Ziekenhuis Gelderse Vallei, Ede, The Netherlands.
4 Department of Gastroenterology and Hepatology, University Medical Center Utrecht, PO BOX 85500, 3508 GA Utrecht, The Netherlands. Electronic address: k.j.vanerpecum@umcutrecht.nl.