Surgery is a cure to UC and the only cure. There are variations of the surgery and in some cases patients end up with "cuffitis" UC of the rectal cuff. If the cuff is stripped (as it was in my case) the disease is gone and I am cured. No more meds nor illness.
Yes, some people's diagnosis changes after the fact. You could wait another 5-7 years before making a decision but at what cost? There are several people on the j-pouch board who had the surgery only later to discover that they had CD. All of them emphatically state they are glad they had the surgery in spite of the change in diagnosis and many of them were able to keep their j-pouches and manage their Crohn's.
It's not an easy decision to make and you and your son need to research the options. It's also a very personal decision.
dx proctitis in 1987
dx UC in 1991, was stable until 1998
1998 started prednisone, asacol, pentasa, nortriptylene, ativan, 6MP, rowasa enemas and suppositories, hydrocortisone enemas, tried the SCD diet, being a vegetarian, omega 3s, flax, pranic healing, yoga, acupuncture, probiotics
2000 lost all my B-12 stores and became anemic
2001 opted for j-pouch surgery- now living life med-free