What is a common cause of dilation in the bile ducts?

Dilation of the bile ducts often occurs due to obstruction, and choledocholithiasis, which refers to the presence of stones in the common bile duct, is a common cause of this condition. When a stone obstructs the flow of bile, it leads to an accumulation of bile above the obstruction, resulting in the dilation of the bile ducts. This can be visualized during an ultrasound examination, where the dilated bile ducts may be seen as a consequence of the obstructive process.

In contrast, cholecystitis primarily involves inflammation of the gallbladder, which can lead to various complications, but it does not typically cause dilation of the bile ducts unless there is an associated obstruction. Gallbladder agenesis refers to the absence of the gallbladder, which does not directly lead to bile duct dilation. Hepatic vein thrombosis primarily affects the hepatic veins and can lead to liver-related complications, but it is not a common cause of bile duct dilation. Thus, choledocholithiasis stands out as the most relevant condition in this context.