Thank you for your query.
Treatment would depend on the diagnosis. However colonoscopy
has ruled out any cause for concern. I suggest that you discuss with the treating doctor and get a proctoscopy done to exclude internal haemorrhoids which can be the cause for bleeding.
I would not recommend any special diet like gaps for a 3 year old child unless the treating doctor recommends.
I hope I have answered your query to your satisfaction.
Wishing your son an early recovery.
Rajiv K Khandelwal