biliary rule 2:Intra and/or extrabiliary obstruction in cholangitis

When you diagnose biliary radicle dilatation affecting one or both hepatic lobes with continuous pattern(dilatation of the duct is continuous to the periphery of hepatic parenchyma), search for type of this dilatation by ERCP or MRCP to exclude or confirm presence of biliary beadings(in case of cholangitis) or mass(in case of cholangiocarcinoma).

In case of presence of beading, diagnose cholangitis.

In case of absence of beading, diagnose obstruction due to other causes.

When you diagnose biliary radicle dilatation affecting one or two lobes of the liver with abrupted terminated pattern(dilatation of the duct is cystic in appearance and give rise to comma shaped lesion  and do not continue to the periphery of the hepatic tissue in addition to the central dot sign)

Here you can diagnose Caroli's disease.

Summary:

-Look first to the periphery of the hepatic parenchyma, to confirm that dilated biliary radicles are reaching this peripheral areas or not.

-If it is occupying these peripheral zones, think about cholangitis versus obstructive mass as cholangiocarcinoma as the cause of this obstruction.

-If it is not occupying these peripheral zones, then thinks about Caroli's disease versus choledochal cyst, where in the former we find cystic dilatation of the ducts with almost comma shaped appearance and central dot sign of portal radicles. While in the latter, we will find dilatation usually extending to the extra hepatic ducts.

Click diagram to enlarge