After any surgery I find it hard to pee,the drugs and truma make it difficult. The best way to get him to pee is in a bathtub with hot water. Of course with surgical wounds this may not be possible even if you could find a tub in todays hospitals. The next best thing is probably a sitz bath with warm water,or even warm wet towels. The trick is to get the muscles that control the bladder to relax.
As for the ileus my son had one also on day 3, hopefully he had a NG tube placed to take pressure off of the bowel. By day 7 we were really getting concerned, what the dr did was to have him get on his hands and knees. The doc then grabbed him by the hips and sharply shook him sideways a few times. He did this to break any early stage adhesions, and or to possibly unkink any part of the intestine. Well it worked.
Hopefully your son will not have to go that long before the ileus clears.
I know it is difficult but do they have him up walking. Walking to get the bowel moving is very important.
Hopefully he is not taking too many narcotics for pain, these also slow down the intestine.
Old Mike