I have had 3 resections and after each one, things were a little looser. It does take a full year or so for the body to recover from any type of major surgery. As others have posted your son should be on some type of long term medication so that the disease can be kept in check and further surgery can be held off for as long as possible.
The other possibility is that your son could be having some bile salt issues. Bile salts are re-absorbed in the terminal ileum so if that is where his resection was, the bile salts could be getting into his large intestine and causing D. There is an off label medication that doctors sometimes prescribe to help. Some of us swear by it, others use it when need be, and for others it doesn't help. Questran. You can talk to your son's doctor to see if this might be the problem.
CD 20 years officially, 30 unofficially. 3 resections '93, '95 '97
Managing with strict low residue diet, keeping symptoms to a minimum. All test show small amount of ulceration, still have occasional blockages. But still have a great time with my 2 daughters and husband!
Prednisone, 6MP,Prevacid, B12 shots, Bentyl, Xifaxan.....