Help me understand intrahepatic PSC vs "small duct" PSC?

So all of my reports say my PSC is and has been for years only in the intrahepatic ducts. But I am pretty sure my doctor told me that does not mean I have "small duct" PSC and in fact, I do not have small duct PSC, but yes, she says, it is limited to my intrahepatic ducts.

I'm confused about this. Anyone know anything about whether there is a variant of PSC limited only to intrahepatic but not actually "small duct" PSC? Is it as simple as there are larger intrahepatic ducts, also, and it would have to be in the smaller intrahepatic ducts to be small duct variant?

You are right - there are larger and smaller intrahepatic ducts. It is called a biliary tree because it narrows down and branches as you get further from the trunk/main hepatic ducts.

Small duct PSC is diagnosed when all other causes are ruled out and everything is pointing to PSC except for imaging which does not show the classic beading. Current imaging can't pick up the smallest branches where the damage is occurring. If your strictures show up on MRCP, you have big duct PSC.

Normal big duct PSC can affect the intrahepatic ducts, the extrahepatic ducts, or both.

Thank you for this. Is there any significance to the fact that all of my tests only show damage in intrahepatic ducts? And I should note that my latest MRCP did show significant beading and truncation in the intrahepatic ducts, so it definitely did show up on imaging. And my last biopsy showed bridging fibrosis and significant ductopenia of small ducts.

I'm not sure how rare or common this is or how it may influence outcome. I can tell you from personal experience that a dominant stricture in the common hepatic duct (extrahepatic) is no fun because it blocks the flow from both lobes.

Hi jp1,

I know this is an old post but I wanted to reply to tell you that I’m in the same boat as you. I have “normal” PSC, so no small-duct but so far all the beading and strictures etc are in my intrahepatic ducts, mostly in the right hepatic duct. I didn’t understand the difference before as well!
Anyway, about your question I do believe there are some advantages to having only psc visible in your intrahepatic ducts, mostly I believe you have less chance of having an cholangitis attack! So that is a plus. I might be wrong though, but I believe I’ve read it somewhere.

Anyway, how have you been? Hope you are doing well and haven’t had much trouble from the psc yet!

Kind regards,

may this picture helps you. small bile ducts αre not depicted here but are more branches of intrahepatic ducts. these are not depicted by mrcp also. sorry gor my bad english

Biliary tract from airwave12