My son has Crohn's and was diagnosed at age 2. I tried to potty train then, but it was a nightmare because he had no control and went about 15 times a day. I tried again at 3 and failed again. By age 4, he communicated better and was able to understand what was happening. He had a reward/sticker chart and I spent a few days putting him on the potty every 15 minutes (very time consuming) and he got it. I felt bad because by this time he was going between 15 and 20 times a day, but always made it to the potty. He got lots of praise/rewards for this because I know how hard it is for him. I would recommend waiting until they are older after age 3 or 4 becuase they understand more. Also, he never had night control so always wore diapers at night even though he was trained during the day. Now with the J- pouch, he has reverted to not being trained. The j-pouch surgery has not helped him and he continues to go 15 times a day except now he has no bowel control so he is in kindergarten in school and has to be pulled from class to be changed. Hope this helps.