What are Biliary Strictures?
A biliary stricture is any narrowing of the bile duct, the tube that carries bile between the liver, gallbladder and duodenum of the small intestine. A minor narrowing does not significantly impede bile movement and a person may be asymptomatic. It is only with a severe degree of obstruction or even complete blockage that symptoms arise.
There are number of reasons why a narrowing may arise. Sometimes it may be due to cancer but a fairly common benign cause is injury to the duct after gallbladder surgery and diagnostic investigations of the biliary tree. . When left untreated it can lead to complications ranging from gallstones to a bile duct infection and even liver abscess.
How Common is a Biliary Stricture?
Gallbladder surgery and related investigations are fairly common procedures. However, bile duct strictures are quite uncommon. The exact prevalence is unknown but it is estimated to occur in about 0.2% to 0.6% of surgical cases. Although strictures can cause severe discomfort and serious complications, it is usually not fatal. The underlying cause is instead more likely to be the cause of death particularly in the event of cancer.
What Happens in Biliary Strictures?
Everyday the liver produces between 600mL to 1 liter of bile. It is a fluid substance composed of waste products, cholesterol and water. The bile is manufactured by the liver cells, collects in channels within the liver (hepatic canaliculi) and drains into ducts within the liver (intrahepatic ducts). These ducts merge and eventually leaves the liver as the common hepatic duct. It is joined by the cystic duct which connects to the gallbladder. Bile can be stored in the gallbladder until it is ready to be expelled into the small intestine. The cystic duct and hepatic duct join to form the common bile duct which in turn joins with the pancreatic duct at the ampulla of Vater.
Picture from Wikimedia Commons
A stricture can occur anywhere along the path of bile flow. When it also obstructs the pancreatic duct, enzymes within the gland may damage it leading to pancreatitis. Strictures may be due to benign or malignant causes. Malignancies are cancerous lesions. However, benign causes of biliary strictures does not mean that it is due to benign (non-cancerous) cause. In fact the most common benign causes are not related to any type of mass or growth. Instead it arises from severe or prolonged inflammation of the bile duct. Inflammation usually arises from an injury, usually associated with surgery or diagnostic investigations.
Inflammation can then lead to the deposition of collagen resulting in scarring of the bile ducts. This is known as fibrosis. The scar tissue can then constrict the duct wall or thicken the wall leading to a narrowing. Sometimes physical obstructions in the bile duct, like gallstones or biliary duct stones, can block the flow of bile even without inflammation. Malignancies of the bile duct or around the duct which then compresses it can also be the cause of a stricture. Impediment of the bile flow leads to cholestasis. The bile can back up in the liver and affect normal cell functions. Obstructive jaundice may therefore occur. Over time this can cause damage to the liver and in some instances even progress to liver failure.
Signs and Symptoms
A slight narrowing of the bile duct may not hamper the flow of bile and therefore the patient is asymptomatic. There may only be symptoms of underlying diseases. The symptoms associated with biliary strictures become noticeable once the narrowing reaches the point that the movement of bile is impeded. The clinical presentation also depends on the complications that develop with biliary strictures.
- Right upper quadrant (RUQ) abdominal pain
- Jaundice – yellow discoloration of the skin and eyes
- Itching skin (pruritus)
- Pale stools and dark urine
- Steatorrhea – fatty stools
- Nausea and sometimes vomiting
- Loss of appetite
- Weight loss
Fatty deposits in the skin (xanthomas) and wasting is more likely to occur in severe and prolonged cases.
Causes of Biliary Strictures
There may be a single stricture or multiple narrowings of the bile duct. The causes can be divided into benign and malignant conditions.
- Surgery – post-operatively especially after surgical removal of the gallbladder (cholecystectomy).
- Iatrogenic – inflammation after endoscopic investigation
- Bile duct infection (cholangitis)
- Bile duct stones (choledocholithiasis)
- Bile duct cysts
- Primary sclerosing cholangitis
- Mirizzi syndrome
- Abdominal trauma
- HIV/AIDS – HIV cholangiopathy
- Liver transplantation (orthotopic)
- Unknown (idiopathic)
- Diseases of the abdominal organs like Crohn’s disease
There are a number of different cancers that can cause biliary strictures. This includes :
- Ampullary carcinoma
- Gallbladder cancer
- Pancreatic cancer
- Mucinous cystadenocarcinoma
- Hepatocellular carcinoma (primary liver cancer)
- Metastatic spread of cancer (secondary cancer)
Diagnosis of Biliary Strictures
The clinical features alone are usually insufficient to reach a conclusive diagnosis of biliary strictures and various diagnostic investigations are necessary. Blood tests, imaging studies and biopsy may be useful in confirming a diagnosis of biliary strictures and the possible cause.
- Blood tests
– alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT)
- Imaging studies and other investigations
– Abdominal CT scan
– Magnetic resonance cholangiopancreatography (MRCP)
– Endoscopic retrograde cholangiopancreatography (ERCP)
– Percutaneous transhepatic cholangiography (PTHC)
– Histologic examination of biopsy sample
Staging needs to be done for cancers causing biliary strictures.
ERCP Picture from Wikimedia Commons
Treatment of Biliary Strictures
The treatment of biliary strictures is directed at the underlying cause. Medication may only be effective when it is directed at the cause and cannot treat the stricture itself. Surgery is usually necessary when conservative management and medical treatment of the underlying cause is not sufficient to resolve the narrowing. Radiation and chemotherapy are other therapeutic measures that may be considered for malignant causes of biliary strictures.
Surgical procedures are aimed at removing the bile duct narrowing and allowing for the bile flow to be restored (decompression). Most of these procedures can be done endoscopically and sometimes during diagnostic investigation of the narrowing. It is important to note that these procedures only aim to relive the bile duct blockage but does not usually attend to the underlying cause. Balloon dilatation and stenting opens the blockage and keeps the duct widened. Sometimes the diseased portion of the bile duct is removed and the remaining portion of the duct joined to the small intestine.