Diagnosis
PSC is generally diagnosed on the basis of having at least two of three clinical criteria after secondary causes of sclerosing cholangitis have been ruled out:
serum alkaline phosphatase (ALP) > 1.5x the upper limit of normal for longer than 6 months
cholangiography demonstrating biliary strictures or irregularity consistent with PSC
liver biopsy consistent with PSC (if available)Historically, a cholangiogram would be obtained via endoscopic retrograde cholangiopancreatography (ERCP), which typically reveals "beading" (alternating strictures and dilation) of the bile ducts inside and/or outside the liver. Currently, the preferred option for diagnostic cholangiography, given its noninvasive yet highly accurate nature, is magnetic resonance cholangiopancreatography (MRCP), a magnetic resonance imaging technique. MRCP has unique strengths, including high spatial resolution, and can even be used to visualize the biliary tract of small animal models of PSC.Most people with PSC have evidence of autoantibodies and abnormal immunoglobulin levels. For example, approximately 80% of people with PSC have perinuclear antineutrophil cytoplasmic antibodies (P-ANCA); however, this and other immunoglobulin findings are not specific to those with PSC and are of unclear clinical significance/consequence. Antinuclear antibodies and anti-smooth muscle antibody are found in 20-50% of PSC patients, and likewise are not specific for the disease,but may identify a subgroup of PSC patients who also have autoimmune hepatitis (i.e. PSC-AIH overlap syndrome).The differential diagnosis can include primary biliary cholangitis (formerly referred to as primary biliary cirrhosis), drug-induced cholestasis, cholangiocarcinoma, IgG4-related disease, post-liver transplantation nonanastomotic biliary strictures,  and HIV-associated cholangiopathy.
Primary sclerosing cholangitis (PSC) is a long-term progressive disease of the liver and gallbladder characterized by inflammation and scarring of the bile ducts, which normally allow bile to drain from the gallbladder. Affected individuals may have no symptoms or may experience signs and symptoms of liver disease, such as yellow discoloration of the skin and eyes, itching, and abdominal pain. The bile duct scarring that occurs in PSC narrows the ducts of the biliary tree and impedes the flow of bile to the intestines. Eventually, it can lead to cirrhosis of the liver and liver failure. PSC increases the risk of various cancers, including liver cancer, gallbladder carcinoma, colorectal cancer, and cholangiocarcinoma. The underlying cause of PSC is unknown. Genetic susceptibility, immune system dysfunction, and abnormal composition of the gut flora may play a role. This is further suggested by the observation that around 75% of individuals with PSC also have inflammatory bowel disease (IBD), most often ulcerative colitis.No effective medical treatment for primary sclerosing cholangitis is known. Its most definitive treatment is a liver transplant, but it can recur after transplantation. Many people affected by PSC require a liver transplant. PSC is a rare disease and most commonly affects people with IBD. About 3.0 to 7.5% of people with ulcerative colitis have PSC, and 80% of people with PSC have some form of IBD. Diagnosis usually occurs in people in their 30s or 40s. Individuals of Northern European ancestry are affected more often than people of Southern European or Asian descent.