Dilated Bile Ducts

Dilated bile ducts can be seen on various imaging studies like ultrasound, CT and MRI.  There are many causes, some of which can be benign and ignored while others can be life threatening and an emergency.   Imaging tests and some more invasive procedures can help sort out the possibilities.

What are bile ducts?

Bile ducts drain bile from the liver and gallbladder to the intestines where they help digest fats. Bile ducts are usually thin, smooth and uninterrupted tubes or pipes that go from the liver, gallbladder and to the intestine.

Dilated common bile duct

The common bile duct starts where the ducts of the gallbladder and liver join and ends in the intestine. The common bile duct can become dilated for various reasons outlined below.

Why do bile ducts get dilated?

The bile ducts can get dilated for various reasons such as a blockage, infection, pancreatitis, functional problem, and medications.

What are the symptoms of dilated bile ducts?

It depends on the cause.  Some patients can be asymptomatic when the bile duct dilation is from a benign cause.  Other patients can present with jaundice or yellowing of the skin and eyes and lab abnormalities.  Some patients may have severe pain.

What do  dilated bile ducts look like on an imaging?

Dilated bile ducts on ultrasound

Ultrasound tests of the abdomen can show dilated bile ducts.  We   Can not always tell why the bile ducts are dilated from an ultrasound test.

Dilated bile ducts on CT

CT scans of the abdomen can show dilated bile ducts.  We can not always tell why the bile ducts are dilated however.  CT is not very good at showing us abnormalities in the bile ducts like stones, areas of narrowing and masses.

Dilated bile ducts on MRI

An MRI that is specially designed to look at the bile ducts is called an MRCP. This is commonly combined with a more general MRI of the abdomen.  This is the best non invasive test for dilated bile ducts.

This is often done because you have right upper abdominal pain, jaundice, lab abnormalities, or an imaging abnormality on another test that needs a closer look.  The MRI will be done in such a way as to best show abnormalities of the bile ducts.

Are dilated bile ducts dangerous or cancerous?

Yes, in some cases dilated bile ducts can be a result of a dangerous condition or cancer.   Further imaging and testing will help determine the cause.

What causes dilated bile ducts?

Stone (choledocholithiasis)

There can be a stone in the bile duct which can cause a blockage, pain, jaundice, lab abnormalities and risk for infection or cholangitis. This will look like a dark round spot in an otherwise bright duct on MRI. A special procedure is often done called an ERCP to remove the stone.

Tumors and cancer

Tumors or cancer that cause blockage of the duct is another common cause. This can occur anywhere along the course of the ducts, but is common in the region of the pancreas.

The bile duct passes through a part of the pancreas called the head. A tumor of the pancreatic head will cause the duct to be obstructed.

A tumor of the bile ducts called a cholangiocarcinoma can also block the ducts.

Masses or tumors that are next to the ducts can also cause a blockage.

Infection (cholangitis)

Cholangitis or infection can cause the bile ducts to be dilated. This is most commonly caused by blockage of the ducts due to stone, tumor or after having an invasive procedure.

A condition called sclerosing cholangitis can cause alternating narrowing and dilations of the bile ducts. The cause is unknown. This condition is chronic and progressive, and a liver transplant is the only cure.

Medications

Dilated bile ducts can also be seen with chronic use of opioid medications, such as those taken for chronic pain.

Sphincter of oddi dysfunction

This can also be seen when the muscle along the bile duct near the intestine causes a blockage. The sphincter muscle does not open when it should causing a backup.   This is called sphincter of oddi dysfunction.

Prior gallbladder surgery (cholecystectomy)

Perhaps the most common benign condition to cause a dilated bile duct is simply having your gallbladder out or cholecystectomy. After the gallbladder is removed, the bile duct may become dilated because you no longer have the gallbladder as a storage site for bile.

Can a dilated common bile duct be normal?

In some cases it can be.  This is especially true if a patient has no symptoms, lab test abnormalities and there is no change in the dilated bile ducts over time on imaging tests.  A dilated bile duct can be normal after you have your gallbladder taken out (cholecystectomy).

How are all the different causes of dilated bile ducts sorted out?

Your clinical presentation will help with narrowing the possibilities and guide further testing.  Imaging will often help with making a diagnosis, especially with conditions like stone in the bile duct or tumor causing a blockage.

Sometimes imaging tests will not detect the cause of the blockage even though there is one. In these cases, a more invasive test called an ERCP is done to look at the bile ducts. This allows direct visualization, biopsy and even therapy.   During an ERCP, a blockage can be treated.  A tube or stent can be placed using an ERCP to bypass the blockage.

Does imaging determine the cause every time?

No.  Sometimes we need more invasive tests to determine the cause of dilated bile ducts like ERCP.  Sometimes the cause is a functional one and has no findings on imaging.

Dilated bile ducts treatment

The treatment will depend on the cause.  Dilated bile ducts which are from a blockage may be bypassed with a stent regardless of the cause.

Growths and tumors may be treated with surgery and systemic therapies like chemotherapy.  Infections will be treated with antibiotics.  Stones in the bile ducts can be removed with an invasive procedure called an ERCP.

Dilated bile ducts : summary

Dilated bile ducts can be found on imaging tests and can have various causes.  MRCP is a specialized MRI which helps with determining the cause.  Common causes of dilated bile ducts include stones, tumors, infections, medications, functional abnormalities, and prior surgery on the gallbladder.  Treatment is aimed at the underlying cause.