I have some experience in this form of play, while this ca be very fun and an interesting and intense form of B & D it does have some inherent risks. "Peter" is correct sterile equipment is a must, whether you boil it, or use disposable catheters is up to you. I like some of the more antique type equipment, having a bit of a antique medical fetish, and have had good success using a bleach and hot water solution for sanitizing of my equipment. Re-usable enema bags should be avoided, there is way to much risk of residual bacteria in the bag and hose, a sealed disposable enema from a medical supplier is probably ok. NEVER inject anything other than sterile water or saline into your bladder big, big no-no! YOUR BLADDER IS A VERY DELICATE AND SENSITIVE ORGAN can be very painful if it is irritated, or injured. When you are filling the bladder be careful not to over fill, if it is getting at all uncomfortable stop!There is no reason to risk an injury, try explaning to the doctor how you managed to cause a tear in your bladder wall.
Most of all remember this pretty much uncharted territory there is not alot of info on this kind of play so proceed with caution and common sense!!!