Catheter-related bladder discomfort (CRBD) is not uncommon in male patients under general anesthesia, and it may cause patient agitation and exacerbated postoperative pain. In this study, the investigators will enroll male patients undergoing elective prostate surgery with urinary catheterization after anesthetic induction, and compare the efficacy of pudendal nerve block (PNB) and intravenous tramadol in prevention of CRBD.