Some people tend to contract an UTI whenever they get an opportunity, while others seem to be more resistant, especially males due to their additional plumbing. Only you can decide if you need to be extra cautious. Maybe you don't.
The problem is that bacteria from your gut will inevitably proliferate in a wet diaper no matter how you try to seperate your mess from your urethra. A wet diaper is a wonderful culture medium. If you are prone to UTIs, consider it contaminated as soon as it is messy.
My suggestions: Drink a bladder equivalent (usually 300-500ml) half an hour before messing, so you make sure you can pee afterwards. Change as soon as possible after messing (or after enjoying, if there's more to it for you). Clean thoroughly. Stay hydrated and rinse your urethra from the inside whenever your kidneys allow it. Don't keep urine in your bladder if there may be pathogens inside it.