This does not sound like pouchitis, which would not resolve on its own in a few days. This seems more diet related or like IPS (irritable pouch syndrome). A good idea is for him to keep a food diary to see if there are any consistent triggers for these episodes. If not, you can assume it is IPS, which is treated the same as IBS. Probiotics may help. Antispasmodics and low dose tricyclic antidepressants can also be prescribed for IPS.
Jan