Had my gallbladder taken out over 30 years ago. had mri recently and results state i have a linear artifact in my bile duct. what can it be?

Clip: It could very well be a surgical clip intentionally placed in that area by your surgeon at that time.

Bile duct: Post surgical artifacts in the bile duct could be due to the surgery itself or could be stone material or bile sludge. Even more rarely it could be a tumor, although they are not usually linear in shape. Your doctor should be able to give you some interpretation based on the appearance of the MRI. Good luck.