Doctors use many tests to diagnose cancer and find out if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
• Type of cancer suspected
• Severity of symptoms
• Previous test results

In addition to a physical examination, the following tests may be used to diagnose bile duct cancer or distinguish it from other possible causes of jaundice (see Symptoms [2]):

Blood chemistry tests [3]. Blood chemistry tests measure the levels of bilirubin and alkaline phosphatase and test other liver functions. High levels of these substances could indicate that the bile duct is not working well.

Tumor marker tests [4] (CEA and CA19-9). Tumor markers are substances found in higher than normal amounts in the blood, urine, or tissues of people with certain types of cancer. Bile duct cancer may cause high levels of carcinoembryonic antigen (CEA) and CA19-9 in the blood. However, a person can have bile duct cancer even if there are normal levels of these markers. Also, high levels of these substances can sometimes occur from diseases other than cancer.

Other tests may be performed to provide more information about the bile duct. These include:

Biopsy [5]. A biopsy is the removal of a small amount of tissue for examination under a microscope. The sample removed during the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease).

The type of biopsy performed depends on the location of the tumor. The doctor can obtain tissue samples during a procedure called a percutaneous transhepatic cholangiography (PTC) or another procedure called an endoscopic retrograde cholangiopancreatography (ERCP). PTC and ERCP are described below. Or, a sample will be taken by using a computed tomography scan (CT or CAT scan; see below) to guide a thin needle biopsy through the skin into the possible tumor to collect a sample of cells.

Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. Occasionally, a biopsy is not possible. In this uncommon situation, people will be treated for bile duct cancer based on other test results and symptoms.

Ultrasound. An ultrasound uses sound waves to create a picture of the internal organs. During an ultrasound, the doctor may be able to see the actual tumor; more often when one of the larger bile ducts is blocked, the small bile ducts behind the blockage get larger. It is this “dilation of ducts” that can be seen on an ultrasound.

To view the bile duct, the doctor may use an endoscopic [6] (a thin, flexible tube inserted through the mouth) or laparoscopic (see below) ultrasound. Both of these procedures allow for a clearer view of the bile duct and can help the doctor perform a biopsy.

Computed tomography (CT or CAT) scan [7]. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a vein to provide better detail. CT scans can also be used to guide a needle biopsy.

Magnetic resonance imaging (MRI) [8]. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. An MRI specific for the bile duct is called MRI cholangiopancreatography. A contrast medium may be injected into a patient's vein to create a clearer picture.

PTC. In this test, a thin needle is inserted into the bile duct in the liver. The doctor injects contrast medium into the needle, which flows into the bile duct. An x-ray is used to show whether the bile duct is blocked and, if so, locate the site of the blockage. This is important in planning treatment.

ERCP. The doctor inserts a flexible tube down the person's throat, through the stomach, and into the bile duct. Dye is injected into the tube, which will help outline the bile duct on an x-ray. A tiny brush can also be inserted through the tube to collect cells and tissue fragments for a biopsy. This technique can help to find and take a sample of the tumor and provide information that is important in planning treatment.

Laparoscopy [6]. The doctor views the bile duct, gallbladder, and liver through a lighted tube inserted into a surgical opening in the person's abdomen. Some laparoscopes can help the doctor to work with small instruments through the tube to take a tissue sample.

Learn more about what to expect when having common tests, procedures, and scans [9].

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer; this is called staging [10]. Learn more about the first steps to take after a diagnosis of cancer [11].