MSFinals-6623

A 27-year-old male patient complains of general malaise and pain in his perineum and scrotum, which started two days ago. He also experiences increased urinary frequency and burning pain while urinating. The patient has no significant medical history. During examination, his heart rate is 75/minute, respiratory rate 16/minute, blood pressure 118/80 mmHg, and temperature 37.6ºC. The prostate is tender and there is boggy enlargement on digital rectal examination. What investigation would be appropriate?