What would cause elevated liver enzyme and dilated cbs?

Several things: Stones in the bile duct when they come out of the gallbladder, sometimes obstruction from different things. Depending on your symptoms- pain, fever, how high the enzymes are- you need ultrasound or other tests.

Stones or tumor: The most common causes of elevated liver enzymes and dilated common bile duct are stones and tumors. Stones can get lodged in the lower end of the bile duct and cause blockage. Tumors can grow there as well, also causing blockage, usually painless. Occasionally inflammation of the pancreas can present the same way as well.

Gallstones: If you mean common bile duct when you say "cbs", then probably the most common thing is a stone from the gallbladder. There are multiple things that can causes elevated liver enzymes alone. The common bile duct can also be dilated normally, but in the setting of elevated liver tests, most commonly it would be from an obstruction of the bile duct.