I had a growth scan at 29 weeks and was told to have a full bladder, which I duly did, only to be told by the sonographer that it was TOO full and that I didn't need it to be full. She said "don't you feel Iike you need to go to the toilet with such a full bladder?". Well YES that is exactly what I feel!
They don't ask for a full bladder at 20wks here either.
I went for my 12 week scan and duly drank the water. And they were running late. After half an hour I asked if it would be much longer. They said no. After an hour I begged to go to the loo, they said no hang on, is imminent and you need a full bladder. Two hours late it was and I was in so much pain I was crying. They told me to go to the toilet (bladder too full) and let out 'a bit'. 3 times I had to go and let out 'a bit'. In the end they decided it would be easier with an empty bladder. Oh God the relief. I sobbed.