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Bilirubin
Alternate Names : Conjugated Bilirubin, Direct Bilirubin, Indirect Bilirubin, Total Bilirubin, Unconjugated Bilirubin
Definition Bilirubin is a breakdown product of hemoglobin. Total and direct bilirubin are usually measured to screen for or to monitor liver or gall bladder dysfunction.
Pictures & Images
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Why is the Test Performed?
This test is useful in determining if a patient has liver disease or a blocked bile duct.
Bilirubin metabolism begins with the breakdown of red blood cells by phagocytic cells. Red blood cells contain hemoglobin, which is broken down to heme and globin. Heme is converted to bilirubin, which is then carried by albumin in the blood to the liver. In the liver, most of the bilirubin is conjugated (chemically attached to) with a glucuronide before it is excreted in the bile. Conjugated bilirubin is called direct bilirubin; unconjugated bilirubin is called indirect bilirubin. Total serum bilirubin equals direct bilirubin plus indirect bilirubin.
Conjugated bilirubin is excreted into the bile by the liver and stored in the gall bladder or transferred directly to the small intestines. Bilirubin is further metabolized by bacteria in the intestines to urobilins, which contribute to the color of the feces. A small percentage of these compounds are reabsorbed and eventually appear in the urine, where they are referred to as urobilinogen.
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Jump to another section
• Definition
• Why is the Test Performed?
• How is the Test Performed?
• How to Prepare for the Test?
• Normal Values
• What do Abnormal Results Mean?
• Special Considerations
• Pictures & Images
Topics that might be of interest to you Diseases & Conditions
• Biliary Obstruction
• Biliary Stricture
• Cholangiocarcinoma
• Cholangitis
• Choledocholithiasis
• Cirrhosis
• Crigler-Najjar Syndrome
• Dubin-Johnson Syndrome
• Erythroblastosis Fetalis
• Gilbert's Syndrome
• Glucose-6-Phosphate Dehydrogenase Deficiency
• Hemolytic Anemia
• Hepatic Encephalopathy
• Hepatitis
• Idiopathic Aplastic Anemia
• Idiopathic Autoimmune Hemolytic Anemia
• Immune Hemolytic Anemia
• Liver Disease
• Newborn Jaundice
• Pernicious Anemia
• Secondary Aplastic Anemia
• Sickle Cell Anemia
• Transfusion Reaction
• Wilson's Disease
Tests & Exams
• Albumin - Serum
• Hemoglobin
• Venipuncture
Other Topics
• Bile
• Caffeine in the Diet
• Fat
• Jaundice - Yellow Skin
• Metabolism
• Niacin
• Sclera
Review Date : 4/29/2003
Reviewed By : Andrew J. Muir, M.D., M.H.S., Division of Gastroenterology, Duke
University Medical Center, Durham, NC. Review provided by VeriMed
Healthcare Network.
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