Been told to go ED for an urg ultrasound re intense to pain liver/gallbladder & can't get apt sooner at radiologist. Can I postpone ed?

Depends. Depends on your symptoms. Vomiting? Eating alright? See your doctor or call your doctor first to determine if it is an emergency. Go to an er if you feel it is an emergency. Yellow jaundice, fever, unrelenting vomiting, unable to eat = go to er.