Sclerosing cholangitis.

A cholangitis is an inflammation of the bile ducts of the liver.

It may be may be primary or secondary. 

Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by inflammation, destruction and fibrosis of the intrahepatic and extrahepatic bile ducts that leads to cirrhosis of the liver.

It may be idiopathic or commonly associated with ulcerative colitis, Crohn’s disease, retroperitoneal fibrosis and Reidel’s stroma. Less common associations include histiocytosis X, angioimmunoblastic lymphadenopathy , and AIDS.

The cause of PSC is unknown but many investigators suspect that it is an autoimmune disease. Other etiologies, such as infectious agents, toxins or recurrent infections of the bile ducts are also possible causes. About 70 % of patients are men and about 75 % of patients with PSC have inflammatory bowel disease, mainly ulcerative colitis.

The term ‘secondary sclerosing cholangitis’ is used to describe the typical bile duct changes described above when a clear predisposing factor to duct fibrosis can be identified.

Causes of secondary sclerosing cholangitis include drugs, bile duct cancers, stone disease, past biliary tree surgery and opportunistic infections of the bile ducts that can cause a similar picture in patients with AIDS. Secondary causes of sclerosing cholangitis must be ruled out when making the diagnosis of PSC.

Pathophysiology:  Bile ducts, both intra- and extrahepatically (inside the liver and outside), are inflamed and develop scarring, obstructing the flow of bile. As bile assists in the enteric breakdown and absorption of fat, the absence of bile leads to fat malabsorption. The bile accumulates in the duct, leading to liver cell damage and liver failure.

Cholangiographic findings change according to the degree of disease.

The most  important  finding is randomly dispersed annular strictures which are not proportional to dilatation proximally. 

- Early in the course of disease, randomly distributed, short, annular intrahepatic stricture

   alternating with normal or slightly dilated segments produce a beaded appearance. 

- As fibrosing process worsens, stricture increases and the ducts become obliterated. 

- With further progression ductal dilatation proximal to stricture results which causes  obstruction. 

Slightly dilated peripheral ducts and  central ducts are not in continuity and this is a characteristic MRCP finding for sclerosing cholangitis .