Bilirubin Urine Test
|See Also||Lab Tests|
Bilirubin is a constituent of bile, which is formed in the liver. The metabolism of bilirubin begins with the breakdown of red blood cells (RBCs) in the reticuloendothelial system. Hemoglobin is then released from lysed RBCs and broken down to heme and globin molecules. Heme is then broken down further to form biliverdin, which is transformed to unconjugated or indirect bilirubin. In the liver, indirect bilirubin is conjugated with glucoronide to produce conjugated or direct bilirubin. The process of excretion of conjugated bilirubin occurs through the liver cells, and into the intrahepatic canaliculi, then to the hepatic ducts, the common bile duct, and the bowel, where it is excreted.,
- Bilirubin identification occurs in routine urinalysis.
- For screening, elevated urine bilirubin concentration can indicate unsuspected liver injury due to disease, gallstones, or drug toxicity.
- Bilirubin in the urine will produce dark yellow or orange urine.
- No food or drink restrictions are necessary.
- Factors which can cause increased levels:
- Drugs: Allopurinol, antibiotics, barbiturates, chlorpromazine, diuretics, ethoxazene, oral contraceptives, phenazopyridine, steroids, and sulfonamides
- Factors which can cause decreased levels:
- Drugs: indomethacine (indocin) and ascorbic acid ( vitamin C)
The bilirubin urine test is used to detect liver injury due to disease, gallstones, or drug toxicity.
High levels indicate:'
- Extrahepatic duct obstruction
- Extensive liver metastasis
- Cholestasis from drugs
- Dubin-Johnson syndrome
- Rotor's syndrome
Low levels indicate:
- None noted
- Pagana Kathleen D., Pagana Timothy J., Mosby's Manual of Diagnostic and Laboratory Tests, Mosby, Inc
- Weatherby Dicken, Ferguson Scott. Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain