This is performed in order to obtain a urine specimen, to check a residual urine volume remaining in the bladder or in the case a patient is unable to urinate. Using local anesthetic jelly a small tube is inserted into the bladder through the urethra. The catheter is then usually removed but may be left indwelling to a bag if the reason for placement was that the patient has been unable to urinate on their own. There is no preparation for this test and you may drive yourself to and from the appointment.