Won’t potty after surgery

My 7 mo old cavapoo male was neutered yesterday. He peed a river outside surgical center yesterday after procedure but has not done anything else since. No food yesterday until 6 pm. He has eaten regularly since, water intake is moderate. But either too stubborn to use the garden or not physically needed. There have been no house accidents as well. Is this reasonable post op? Also, how stringent does the “no walks” rule need to be. I think if he has a walk he will do what he needs.