Topic: Organ Function Tests
Question: Define and classify jaundice. Describe the clinical tests and their interpretations?
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Jaundice is a medical condition characterized by a yellowish discoloration of the skin, mucous membranes, and sclera (the white part of the eyes) due to an excess of bilirubin in the body. Bilirubin is a yellow pigment that’s produced when the liver breaks down old red blood cells.
Jaundice can be classified into three main types based on the underlying cause:
- Pre-hepatic jaundice: This type of jaundice is caused by conditions that increase the production of bilirubin, such as hemolytic anemia. In pre-hepatic jaundice, the liver is unable to process the excess bilirubin, leading to its accumulation in the body.
- Hepatic jaundice: This type of jaundice is caused by conditions that affect the liver’s ability to process bilirubin, such as hepatitis, cirrhosis, or liver cancer. In hepatic jaundice, the liver is unable to conjugate (process) bilirubin, leading to its accumulation in the body.
- Post-hepatic jaundice: This type of jaundice is caused by conditions that obstruct the bile ducts, preventing bilirubin from being excreted into the intestine. In post-hepatic jaundice, bilirubin accumulates in the body because it’s unable to leave the liver.
Clinical tests for jaundice include:
- Physical examination: A physical examination can reveal the presence of jaundice by observing the color of the skin and sclera.
- Blood tests: Blood tests can measure the level of bilirubin in the blood. An elevated bilirubin level indicates the presence of jaundice.
- Liver function tests: Liver function tests can measure the levels of various enzymes and proteins in the blood, which can help to determine the cause of jaundice. For example, an elevated level of alanine aminotransferase (ALT) or aspartate aminotransferase (AST) may indicate liver damage, while an elevated level of alkaline phosphatase (ALP) may indicate obstruction of the bile ducts.
- Imaging tests: Imaging tests, such as ultrasound, CT scan, or MRI, can help to identify any structural abnormalities in the liver or bile ducts that may be causing jaundice.
The interpretation of these tests depends on the underlying cause of jaundice. For example, in pre-hepatic jaundice, the bilirubin level is usually elevated, but the liver function tests are normal. In hepatic jaundice, both the bilirubin level and the liver function tests are usually elevated. In post-hepatic jaundice, the bilirubin level and the ALP level are usually elevated, while the other liver function tests may be normal or only mildly elevated.
