Mine too is for a blocked bile duct. I am not sure what eactly causes it but they explained it as a sludge backup. They had me on ursidiol for awhile to help keep sludge from building up. However they doubled my dose before my ERCP in February which caused me to have a severe itching equivalent to itch when my liver went bad. Shots of benadryl stopped working as i was hospitalized. Thats when they dicovered it was the large dose of Ursidiol making me itch. Hang in there and I hope these get easier for you.