What Causes Difficulty In Viewing Gallbladder During Ultra Sound Scanning?

Hi, I had HIDA scan done this week and my gallbladder did not show up until 2 hours into scan. They did not do next part of test because they said this was abnormal. I did drink about 8 oz of tea about 3 hours prior to test, could this be the cause of it taking so long for it to show? Also, I have just recently found out that I have PVCs. Can this be related to my gallbladder issues?
Thanks!