Intrinsic to the ductal system
	Gallstones
	Surgical strictures
	Infection (cytomegalovirus, Cryptosporidium infection in patients with acquired immunodeficiency syndrome)
	Intrahepatic malignancy
	Cholangiocarcinoma
Extrinsic to the ductal system
	Extrahepatic malignancy (pancreas, lymphoma)
	Pancreatitis