Some doctors want you to use some form of laxative or other bowel-cleanout preparation. But not every doctor does, and those who want you to will tell you. It depends very much on the doctor's preferences and what you're having done during your hyst. If you do something on your own, you risk going into surgery dehydrated or otherwise with your system in imbalance. If you are concerned about this, call your doctor's office and specifically ask if you are to do a "bowel prep." follow their directions exactly. If there is no prep ordered by your doctor, don't do one.