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Diagnosing PSC

Diagnosing PSC

A sound and thorough diagnostic workup allows the experienced specialist to tailor PSC management just for you. Because misdiagnosis of PSC is common, you may have identified your disease through a long and frustrating route. The steps and tests commonly used to diagnose and assess PSC are briefly mentioned below:

  • Medical history and physical

A history and physical wherein the medical team will ask about symptoms, family history, and diseases that can be associated with PSC, among other questions.

  • Blood tests

Blood tests are used to examine liver function and inflammation (as well as the status of other organ systems). These tests include ALT (alanine aminotransferase), AST (aspartate aminotransferase), ALP (alkaline phosphatase, also abbreviated as ALK), GGT (gamma-glutamyltranspeptidase), and bilirubin.

  • ERCP

Endoscopic retrograde cholangiopancreatograph (ERCP) or magnetic resonance cholangiopancreatography (MRCP) are specialized procedures to examine your bile ducts and determine if, where, and to what extent they have become injured/affected as a result of PSC.

  • Colonoscopy

Because PSC is often associated with inflammatory bowel disease, especially ulcerative colitis, a colonoscopy may be recommended to see if you have this condition.

  • Liver biopsy

If the above have been performed but the diagnosis cannot be established or more information is needed, a liver biopsy may be pursued.

PSC Stages

PSC is often “staged”, which refers to the degree to which the disease has progressed (i.e. from very early to very advanced) with respect to scar tissue formation (i.e. “fibrosis”).  This is typically based on a liver biopsy and categorized as follows:

Stage 1 – A small amount of fibrosis limited primarily to regions in the liver called “portal areas”.

Stage 2 – Fibrosis begins to appear outside the portal areas. The strands of fibrosis are not yet connected to each other.

Stage 3 – Areas of fibrosis connecting to each other.

Stage 4 – Widespread, honeycomb like scarring known as cirrhosis.

Serum liver tests

If a liver problem is suspected, one of the first things your doctors will do is test your blood and examine the results of your serum liver tests, often referred to as “liver function tests”, or LFTs. This term broadly refers to a panel of blood tests which provide not only an indication of liver function, but also liver inflammation, blockage of bile flow, and other parameters. If the values are outside or above the normal range, this may indicate a liver problem, among other possible explanations, as discussed below:

  • GGT

Gamma-glutamyl transpeptidase (note: you don’t have to bother with the full names, GGT is used universally): This is an enzyme (a protein that helps carry out biochemical reactions or processes) which is found mainly in liver and bile duct cells (hepatocytes and cholangiocytes, respectively) and is very sensitive to (i.e. rises in the context of) liver injury and decreased bile flow. In the majority of individuals with PSC, GGT will be elevated above the normal range because PSC involves inflammation and damage to the bile ducts; however, it is not checked as often in adult patients as it is in pediatrics.

  • ALT (also abbreviated SGPT)

Alanine aminotransferase: This is an enzyme mainly found within liver cells.  Elevations in ALT usually indicate liver and/or bile duct inflammation. Aspartate aminotransferase (AST, also referred to as SGOT) is a similar enzyme but is less specific to the liver since it is highly expressed in other tissues such as muscle.

  • ALP

Alkaline phosphatase: This is an enzyme expressed on the surface of liver and bile duct cells (as well as bone, placental, and other cells). ALP is typically elevated when there is a problem with bile flow, including bile duct blockages, such as may be seen with as a result of strictures, stones, or masses.

  • Bilirubin

Bilirubin is a yellow pigment and a normal byproduct of red blood cell metabolism. Red blood cells normally last in the circulation for about 3 months, after which they are broken down and recycled. One of the components of red blood cells, hemoglobin, is broken down into bilirubin through a series of biochemical reactions. Bilirubin is transported to the liver, where it is processed further (i.e. “conjugated”) and then secreted into bile. If bilirubin cannot be effectively transported via the bile ducts, bilirubin levels in the blood may rise, jaundice (skin yellowing) begins to appear, stools may become grayish white, and urine may turn a dark orange color.

  • Albumin

Albumin is made by the liver and constitutes the main circulating protein in human blood. Low blood albumin levels may represent problems with liver function, although they can also be due to kidney failure, chronic infection, and various other causes.

  • PT and INR

Prothrombin time and international normalized ratio: PT measures how long it takes plasma to clot, with most clotting factors being made by the liver. While the usual reference range for PT is 12-15 seconds, because there can be variation in laboratory methods and materials, the INR is used as a means to standardize the PT (and is thus more universally applicable). As with albumin, PT and INR can be affected by various things aside from liver function, including but not limited to medications and heart function.

In a similar way to blood pressure, the aforementioned liver test results will usually vary over time, and trends over time (i.e. over the course of days to months) are typically more important than individual values. There are many other blood tests that your doctors may order, but these are the main ones which should be monitored on a regular basis. Further information can be found online at Lab Tests Online (www.labtestsonline.org).