Choledocholithiasis · What Is It, Causes, Diagnosis, Treatment, and More

Choledocholithiasis occurs when a stone blocks the bile flow through the common bile duct. Most often, gallstones form in the gallbladder and then migrate to the common bile duct, where they get stuck. However, they can also form in the common bile duct itself, which is why choledocholithiasis can still occur for people who have had their gallbladders removed. 

Gallstones occur when there’s an imbalance in the composition of bile, which leads to sedimentation and formation into stones. Risk factors for developing gallstones include sudden weight loss; obesity; dietary factors like high-calorie diets; liver disease; and medications containing estrogen like oral contraceptives or hormonal therapy.  

There are three different types of gallstones, classified according to their cholesterol composition. Cholesterol gallstones are made up of more than 80% cholesterol and are the most common type of stone. Mixed gallstones consist of between 30–80% cholesterol, and also contain calcium salts and biliary acids. Finally, pigment gallstones are composed primarily of bilirubin salts; they have less than 30% cholesterol. 

Diagnosis of choledocholithiasis is suspected when an individual presents with colicky pain in the right upper abdominal quadrant, along with intermittent episodes of jaundice due to the build-up of bilirubin in the blood. In addition, some individuals may present with dark urine as a result of the excess bilirubin being excreted in the urine; as well as pale stools, since bilirubin is not able to flow into the gastrointestinal tract. History will often reveal the onset of symptoms after eating a high fat meal. 

To identify choledocholithiasis, blood tests can be done to look for high levels of bilirubin and liver enzymes (e.g., ALT, AST, GGT and ALP), as well as signs of inflammation, such as leukocytosis and elevated CRP. Initially, a transabdominal ultrasound can be performed to look for dilation of the common bile duct, which is an indirect sign that a stone has been ejected from the gallbladder and gotten stuck downstream. In general, common bile duct stones can be difficult to visualize. If visible, they typically appear as bright, hyperechogenic structures with a dark shadow behind them known as posterior shadowing.   

If diagnosis is unclear, other imaging techniques can be performed to evaluate the biliary and pancreatic ducts. Diagnostic tests include non-invasive techniques, like endoscopic ultrasound (EUS) or magnetic resonance cholangiopancreatography (MRCP), as well as invasive techniques like endoscopic retrograde cholangiopancreatography (ERCP) or intraoperative cholangiography. If possible, non-invasive techniques are preferred, since they have a lower risk of complications.  

Due to their small size or composition, some gallstones may not be detectable on standard imaging techniques. In highly symptomatic individuals without evidence of gallstones, cholescintigraphy with a HIDA scan (hepatobiliary iminodiacetic acid scan) should be considered. A HIDA scan is a nuclear medicine technique that uses a radioactive tracer (iminodiacetic acid [IDA]) to track the flow of bile from the liver to the small intestine. The absence of tracer in the small intestine suggests an obstruction in the biliary tract.  

In some cases, small stones can spontaneously pass into the duodenum, relieving the obstruction. However, most cases need stone removal through ERCP or surgery.  

ERCP uses an endoscopic guide to perform a small opening in the biliary tract, so that the stones can pass more easily. ERCP is highly successful, but it can have complications like pancreatitis, bleeding, and rupture of the duct.  

Stone removal is most often followed by gallbladder removal surgery (i.e., cholecystectomy) to prevent the recurrence of stones.