For transvaginal ultrasound you can have an empty bladder Dating scans are usually recommended if there is doubt about the validity of the last menstrual period.
For example if you a tiny sac can be seen in the uterus, but the baby and its heart beat may not be detected yet.
the baby and its heart beat can be detected relatively easily with trans-abdominal and trans-vaginal examination.
This is presuming that the pregnancy is actually at this stage of development.
If you’re expecting, you’ll likely have an ultrasound at some point during your pregnancy.
(Fun fact: some people use the term “sonogram” interchangeably with ultrasound—sonograms are the images created during an ultrasound!
Your bladder should not be so full that it causes pain.