Even if recommended by your doctor, it is always your choice whether or not to have this procedure. But, it is important to understand the possible consequences involved with this decision.
If you decline the procedure, you are limiting your doctor's ability to obtain key information about your condition. In your doctor's opinion, this information is necessary to develop the best treatment plan for your symptoms.
Yet, the final decision to have or not to have this procedure rests with you. All of your concerns related to this decision should be discussed with your doctor at length. Then you and your doctor can come up with a treatment method that is comfortable for you.