Cancer of the bile duct can be difficult to diagnose, so you may need several tests, including: blood tests ultrasound scans computerised tomography (CT) scans magnetic resonance imaging (MRI) scans For some of these tests, you may need to be injected with a special dye that highlights your bile ducts. You may also need a biopsy. This involves removing a small sample of tissue so it can be studied under a microscope. However, in some cases, your surgeon may prefer to remove the suspected tumour based on the results of your scans alone.