Bilirubin is a waste product resulting from the lysis of red blood cells and the release of hemoglobin. The heme (iron) portion of the hemoglobin molecule is converted into the bile pigment bilirubin . Bilirubin is a yellow pigment. An abnormally increased blood concentration creates a jaundiced discoloration of the skin, whites of the eyes, and mucous membranes.
Bilirubin is eliminated from the body through a complex process involving the liver.
Bilirubin is eliminated from the body through a complex process involving the liver.
There are two main forms of bilirubin: indirect or unconjugated
bilirubin, which is transported to the liver as a bilirubin-albumin
complex and converted to direct or conjugated bilirubin that is eventually excreted in feces and urine.
bilirubin, which is transported to the liver as a bilirubin-albumin
complex and converted to direct or conjugated bilirubin that is eventually excreted in feces and urine.
Liver malfunction can inhibit this process . Consequently bilirubin will not be converted to excretable products and will accumulate
in the blood.
Bilirubin testing can include measuring the levels of indirect bilirubin, direct bilirubin, and total bilirubin, the sum of direct and indirect bilirubin.
in the blood.
Bilirubin testing can include measuring the levels of indirect bilirubin, direct bilirubin, and total bilirubin, the sum of direct and indirect bilirubin.
Normal Range
Total bilirubin
0.2-1 .0 mg/dl
Indirect bilirubin
0.1-0.7 mg/dl
Direct bilirubin
0.1-0.3 mg/dl
Newborn total bilirubin
1-12 mg/dl
Diagnostic Application
Destruction of RBCs; liver dysfunction Liver and kidney functions
Kidney excretory function; decreased muscle mass Diagnostic for gout
Variations from Normal.
Elevated indirect bilirubin is usually associated with increased destruction of red blood cells, destruction of hemoglobin as seen in hemolytic anemias, pernicious anemia, sickle cell anemia, transfusion reactions, and hemolytic disease of newborns.
Abnormally elevated indirect bilirubin concentrations may also indicate liver dysfunction in that the liver is unable to convert indirect bilirubin to direct bilirubin. Hepatic diseases associated with elevated indirect bilirubin include hepatitis, cirrhosis, and extensive liver tumors.
An increase in direct bilirubin levels usually indicates an inability to excrete bilirubin . Gallstones, tumors, bile duct obstruction, and cancer of the pancreatic head can cause increases in direct bilirubin.
Abnormally elevated indirect bilirubin concentrations may also indicate liver dysfunction in that the liver is unable to convert indirect bilirubin to direct bilirubin. Hepatic diseases associated with elevated indirect bilirubin include hepatitis, cirrhosis, and extensive liver tumors.
An increase in direct bilirubin levels usually indicates an inability to excrete bilirubin . Gallstones, tumors, bile duct obstruction, and cancer of the pancreatic head can cause increases in direct bilirubin.
Interfering Circumstances.
Improper handling of the blood sample can alter test results . Exposure of the specimen to sunlight or high-intensity artificial
light at room temperature will decrease bilirubin concentration .
Shaking the blood specimen and the presence of air bubbles may also decrease bilirubin levels.
Drugs that cause increased bilirubin include allopurinol, anabolic
steroids, ascorbic acid, diabinese, codeine, steroids, diuretics, and oral contraceptives
. Drugs associated with decreased levels are barbiturates, caffeine,
penicillin, and high doses of salicylates.
light at room temperature will decrease bilirubin concentration .
Shaking the blood specimen and the presence of air bubbles may also decrease bilirubin levels.
Drugs that cause increased bilirubin include allopurinol, anabolic
steroids, ascorbic acid, diabinese, codeine, steroids, diuretics, and oral contraceptives
. Drugs associated with decreased levels are barbiturates, caffeine,
penicillin, and high doses of salicylates.
