Think you need to talk to your GI again and ask if it is def CD or possibly UC and if it is CD why he thinks good idea so you know in your mind why he is recommending meds. I take azathioprine which is an immunosuppresant to keep CD in remission and it has done very successfully for many years. Only had flare last year when I stopped it as had been in remission of 6 years as GI felt maybe could cope without it. Bad idea. Now back on it and also took Humira for 6 months (stopped that due to horrendous side effects) and back in remission.
A lot of GI think even if your colon is the only part affected and that is removed and you def have CD and not UC then preventative medication is good idea as CD can work at a microscopic level and take many years to cause a flare that you would notice but as it has been left for so long without treatment it can take long time and major meds to get it back into remission.
I only know what my CD is like and that is if it is left to it's own devices then it will misbehave very quickly and so that is why I will always have to take azathioprine for life. It keeps my disease under control.
Crohn's dx 1989, loop ileo 1992, end ileo 1992. Arthritis developed 1990 Stoma abcess 1995. Azathioprine started 1995. Panprocolorectomy 1999. Stillbirth 2000, antiphospholipid syndrome dx 2000. Flare up 2004, stoma abcess and strictoplasty 2004. Low blood pressure dx with impaired kidney function 2006, fludrocortisone pres. flare up 2010, steroids, Humira, codeine.