@lvoss:
I understand and that is my vet's first choice also but sometimes it is the only thing that will show a blockage. The other thing would be is there an ultrasound specialist in the area. My vet will do ultrasound themselves for many things but in difficult cases they will bring in a specialist because often times they will see things that others will miss.
My Vets are the same, while they do some ultrasound, usually they schedule a specialist once a week, if something is more of any emerency, then we go to the specialist. Lucky that we have two to choose from that are pretty close. Also, when we were trying to find Kristii's problem a few years ago (very similar to this boys problem), the barum did move through, however with the ultrasound they immediately saw the blockage and we knew surgery was needed asap…. Regardless, sounds like your Vet is on top of trying to get to the bottom of the problem.....