Primary sclerosing cholangitis: A chronic disorder of the liver of uncertain cause in which the bile ducts within and outside of the liver become inflamed, thickened, scarred (sclerotic), and obstructed. This progressive process can in time destroy the bile ducts and lead to cirrhosis. Abbreviated PSC. PSC can occur by itself or in association with other diseases, including inflammatory bowel disease. PSC often triggers jaundice (yellowing), pruritus (generalized itching all over the body), upper abdominal pain, and infection. Later on, PSC progresses to cirrhosis of the liver and liver failure, creating a need for liver transplantation. Diagnosis is made via clinical observation and routine laboratory tests and is confirmed through demonstration of thickened bile ducts, using special radiologic tests called cholangiography. Treatment includes cholestyramine to diminish itching, antibiotics for infection, vitamin D and calcium to prevent bone loss (osteoporosis), sometimes balloon dilatation or surgery for obstructed ducts, and liver transplantation when necessary and possible. The prognosis depends on the age of the person, the degree of jaundice, the stage of PSC found via liver biopsy, and the size of the spleen. Most patients die within 10 years of diagnosis unless a liver transplant is performed. Also known as idiopathic sclerosing cholangitis.