I personally have experienced no difficulties with my urostomy with regard to airport security and I have travelled extensively wordwide. My worst experience (if you can call it that) was when a young man on security at Heathrow Airport emptied out my hand luggage in full view of other travellers which included my spare flanges etc and he demanded to kow what they were used for. I was mildly embarrassed and he seemed slightly perpplexed but was happy enough with my explanation and let me through.
I have been through the 'naked' scanners and have held my breath but I have never been taken aside. I frequently get 'patted down' going through the metal detector thing. At first I used to worry that the official would feel my bag and I would be embarrassed or flustered. However, every pat down I have received has taken seconds and to be honest, if they have felt the bag, they have not acted on it. Now I am totally unconcerned with airport security on a personal level, I think this is a mixture of age and experience! And if I do ever have to explain myself, well, it's better for the security officials to be safe rather than sorry. I remind myself they are for the good of us all. I have heard in the past of some sort of travel card for people with an ostomy - this gives information on the subject and can be presented to security staff to help with explanations. I have never bothered with this. I expect in this day and age security staff are aware of ostomies and have encourtered at least one?
I hope the above brings you a bit of reassurance and hopefully you will get responses from people who have had more challenging times at airports, just to get both sides. Most of all I hope you enjoy your trip to Italy.