I've had more ultrasounds than I can count in the last year!! It seems to me if I have the ultrasound done in the afternoon, I'm fine. If I have it in the morning, thats when I seem to have problems! I typically have a BM after breakfast anyways and I think all the water before going potty gives me D. Its not the D itself that is so terrible, its having D BEFORE the ultrasound and not being able to pee!
Since yours is in the afternoon, you should be fine!! Just eat a light lunch and be sure to try and go potty before you start drinking your water! Let us know what you find out!
-------------------- Taking it one day at a time.....