This may be a difficult one to find many people with experience. (I was surprised you had any so far!) My mother was diagnosed a little over 10 years ago after a couple years of doctors missing the symptoms. She probably developed DI as a result of chemotherapy damaging her pituitary. Has your son had this confirmed with a test yet. In her case they had her stay in the hospital overnight, did not allow her to drink water and checked her blood for a particular hormone overnight. When she was untreated she used to describe her thirst as "wanting to put her face in a watermelon and suck all the water out." She would drink ALOT of water. At the time she was diagnosed there were only 25,000 cases in the US. She was actually living overseas when it was finally diagnosed. I can offer some advice from her experience.
1) Get a good endocrinologist (prob the specialist mentioned). Endocrinology can be an art form. Just like diabetes mellitus (sugar diabetes) your body would normally adjust a certain hormone (in this case vasopression) through-out the day. With DI you are generally taking a medication once or twice a day to ensure your body retains water. Without medication your body does not reabsorb water from your kidneys and you expel it...frequent urination.
2) If you son says he is thirsty. Get him water. It would be good for him to keep a bottle with him when he starts school. When he exercises (sweating) or is in the sun alot he should just drink water regularly.
3) There is a national support group. My mother received a newsletter...You can check online and they may have chat group. I would ask her for you but she passed away 4 years ago...completely unrelated to this condition.
4) DI is something doctors learn about in med school...I learned about it in my physiology class as an undergraduate. It makes a great test question but most doctors will never see the condition and many may forget about it. When ever you see a nurse or doctor about something else and you mention DI we would always follow that with "you know, WATER Diabetes." Sometimes folks hear diabetes and tune out the rest.
This is a very RARE condition. After the initial test...I'm not sure if they do the hospital stay here with kids, again she was overseas, they may also do a CAT scan. This is not horrible, honest. They just usual want to determine if the problem if with the pituitary or the kidneys. Normally our pituitary sends a hormone signal to the kidneys to determine when we should retain water. In my mothers case her pituitary just didn't send the hormone so she took it nasally and then I think a pill form became available.
Again, find a endocrinologist you like. Don't be intimidated by the condition. If this is the diagnosis read-up online and find the support group...oh found them in google
www.diabetesinsipidus.org
My mother was much more comfortable once she was diagnosed and medicated. She didn't have to get up numerous times at night to urinate and stopped drinking a gallon of water at a sitting.
Hope this long message helps. Yet again, this is very rare to wait to hear what the endocrinologists says and it should definitely be managed by a specialist. It is managable. Hope all goes well!
D.