Urine Bilirubin

Sample for urine bilirubin

1. The sample is urine.
2. A random sample can be taken.

Precautions for urine bilirubin

1. A fresh urine sample is needed.
2. Store at 2 to 8 °C for no longer than 24 hours.
3. Even at room temperature, it converts into biliverdin.
4. Avoid urine to light. Avoid daylight or fluorescent light.
   1. Light converts bilirubin to biliverdin, which is not detected by routine methodology.
5. Exposure to light urine will decrease bilirubin.

The false-positive:

1. A false positive result is seen in the metabolites of drugs like phenazopyridine.
   1. The substances which color the urine red or turn red in the acid medium like:
      1. Chlorpromazine.
      2. Phenothiazine.
      3. Indol.
      4. Pyridium

False-negative:

1. False-negative results are seen:
   1. With the ascorbic acid intake.
   2. Oxidation of bilirubin to biliverdin.
   3. Increased nitrite concentration.
   4. Hydrolyzation of bilirubin diglucuronide to free bilirubin.

Indications for urine bilirubin

1. Diagnose hepatitis.
2. Diagnose any liver damage.
3. Monitor the treatment of hepatitis.

Definition of urine bilirubin

1. It is the conjugated bilirubin that is excreted from the kidneys and appears in the urine.
2. Unconjugated bilirubin can not pass the glomerular filtration, so it is not present in the urine.

Pathophysiology of bilirubin metabolism

1. A detectable amount of bilirubin is not found in the urine.
2. The breakdown of hemoglobin leads to bilirubin formation, which goes to the liver.
   1. From the liver excreted into the bile.
   2. Excretion of bilirubin is seen in obstructive jaundice and not in hemolytic jaundice unless there is liver damage.

1. Following the diagram explains bilirubin metabolism and its excretion.

Clinical significance of urine bilirubin:

1. Urine bilirubin is the early sign of:
   1. Hepatocellular disease.
   2. Intra or extrahepatic biliary obstruction.
2. Bilirubin appears in the urine before other signs of hepatitis appear.
3. Bilirubin’s presence or absence in the urine is helpful for clinical jaundice.
4. Bilirubin is the major component of bile.
5. If there is an obstruction to the bile, that will lead to conjugated hyperbilirubinemia.

6. Conjugated bilirubin is water-soluble, so that it will appear in the urine.
7. The presence of bilirubin in urine indicates defects after conjugation and defects in excretion.
8. Bilirubin is a yellowish pigment in the bile which is produced by the liver.
9. Bilirubin in urine color = dark yellow or orange.
   1. This test measures the amount of bilirubin excreted in the urine.
   2. The presence of bilirubin in the urine indicates jaundice.

Normal urine bilirubin

• Normally bilirubin is absent in the urine (0 to 0.02 mg/dL or 0 to 0.34 µmol/L).
• Even traces indicate liver disease like hepatitis.

Procedure for urine bilirubin:

The following tests are used to check bilirubin in the urine:

1. Fouchet’s test.
2. Strip method.
3. Tablet method.

Tablet method

1. In this test, bilirubin form stable diazonium salt that produces blue-purple azobilirubin.
2. This reaction is specific to bilirubin.
3. Read the result after 60 seconds.
4. Moisture will deteriorate the reagents.
5. Always use a white dry tablet.
6. It detects the urine bilirubin level as low as 0.5 mg/dL.

Fouchet’s or Ferric chloride reaction:

1. Add urine to barium chloride, and it will form a barium sulfate precipitate containing bilirubin.
2. Barium sulfate + bilirubin filter and get the precipitate.
3. Add ferric chloride (Fouchet’s solution) to the above precipitate.
4. Bilirubin oxidized to biliverdin, which gives green-blue color.

Comparison of Fouchet’s reaction and Diazo’s reaction:

The  various strips detection level:

Increased urine bilirubin is seen in:

1. Hepatitis and liver diseases are caused by infection or exposure to toxic agents ( cirrhosis ).
2. Obstructive biliary tract disease.
3. Liver or biliary tract tumor.
4. Septicemia.
5. Hyperthyroidism.
6. Gallstones.
7. Metastatic tumor in the liver.
8. Drugs
9. Dubin-Johnson syndrome.
10. Rotor syndrome.

Urine Bilirubin/urobilinogen differential diagnosis

• Urine bilirubin is negative in hemolytic disease.

Bilirubin (urine and blood) in various types of jaundice:

Questions and answers: