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Urine Bilirubin, Bilirubinuria

April 29, 2022Lab TestsUrine Analysis

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, and this is not detected by routine methodology.
  5. Exposure to light urine will decrease the bilirubin.
  6. The 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
  7. 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. The detectable amount of bilirubin is not found in the urine.
  2. 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.
  3. Following the diagram explains bilirubin metabolism and its excretion.
Bilirubin metabolism summary

Bilirubin metabolism summary

Urine bilirubin metabolism

Urine bilirubin metabolism

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.
Obstructive jaundice

Obstructive jaundice

  1. Conjugated bilirubin is water-soluble so it will appear in the urine.
  2. So the presence of bilirubin in urine indicates defects after conjugation and defects in excretion.
  3. Bilirubin is a yellowish pigment in the bile which is produced by the liver.
  4. 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:

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 of this table.
  5. Always use a white dry tablet.
  6. It detects the urine bilirubin level as low as 0.5 mg/dL.
Urine bilirubin tablet test

Urine bilirubin tablet test

Strip method:

  1. These are mostly available as multiple test strips.
  2. This reaction depends upon the diazo reaction. These strips are impregnated with the diazo reagent.
  3. This method detects the concentration of 0.5 mg/dL or greater.
  4. Insert the strip in the urine no longer than one second.
  5. After 60 seconds, the Diazo reagent reacts with bilirubin at an acidic pH.
    1. A pink to red-violet color is produced.
  6. The intensity of the color depends upon the concentration of the bilirubin in the urine.
Urine bilirubin strip method

Urine bilirubin strip method

Fouchet’s or Ferric chloride reaction:

  1. Add urine to barium chloride, and it will form 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.
Fouchet's reaction

Fouchet’s reaction

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

Characteristics Fouchet’s reaction (FeCl3) Diazo reaction
  • The sensitivity of the tests
Many other compounds give a positive reaction with FeCL3 with different colors.

A tablet test is more sensitive than a dipstick

Tablet test = 0.2 to 0.4 mg/dL

Dipstick test = 0.05 to 0.1 mg/dL

  • False-negative result
Oxidation of the bilirubin in case of delayed testing
  1. Vitamin C (ascorbic acid)
  2. The increased amount of nitrite
  3. Oxidation of bilirubin in case of delayed testing >4 hours
  • False-positive result
  1. Urobilinogen
  2. urobilin
  3. Aspirin metabolites
Chlorpromazine

The  various strips detection level:

Type of the strip The detection level of bilirubin
Ictotest 0.05 to 0.1 mg/dL
Multistix 0.4 to 0.8 mg/dL
Chemstrip 0.5 mg/dL

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

Test Normal Conjugated (Direct) hyperbilirubinemia Unconjugated (Indirect) hyperbilirubinemia Conjugated (Direct) hyperbilirubinemia
Etiology Biliary obstruction Hemolysis Hepatitis (liver injury)
Urine bilirubin negative positive (Increased) Usually absent positive
Urine urobilinogen positive / negative Absent Positive (Increased) positive (+++)
  • Urine bilirubin is negative in hemolytic disease.

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

Type of the jaundice Etiology Urine bilirubin Urine urobilinogen Blood bilirubin Fecal appearance
Hemolytic or prehepatic
  1. Hemolytic anemia
  2. Hemolytic anemia of the newborn
Negative (Usually absent) Increased Raised Dark brown
Hepatic or hepatocellular
  1. Physiologic jaundice in neonates
  2. Viral hepatitis
  3. Toxic hepatitis
  4. Cirrhosis

Increased (variable)

(+ or -)

Increased

(++)

An increased, variable amount Normal or pale
Post-hepatic or obstructive
  1. Gall stones
  2. Malignancy
Increased (+++) Absent (or very low)
  1. Direct increased
  2. Indirect normal or slightly increased
Clay-colored, acholic

Normal urine picture:

Physical features Chemical features Microscopic findings
  1. Color = Pale yellow or amber
  2. Appearance = Clear to slightly hazy
  3. pH = 4.5 to 8.0
  4. Specific gravity = 1.015 to 1.025
  1. Blood = Negative
  2. Glucose = Negative
  3. Ketones= Negative
  4. Protein = Negative
  5. Bilirubin = Negative
  6. Urobilinogen = Negative (±)
  7. Leucocyte esterase = Negative
  8. Nitrite for bacteria = Negative
  1. RBCs = Rare or Negative
  2. WBC = Rare or Negative
  3. Epithelial cells = Few
  4. Cast = Negative (Occasional hyaline)
  5. Crystal = Negative (Depends upon the pH of the urine)
  6. Bacteria = Negative
Summary of the urine analysis

Summary of the urine analysis


Possible References Used
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Comments

LC Reply
April 5, 2021

I think there is a mistake in the table comparing bilirubin and urobilinogen in the urine.
in obstructive jaundice, the urobilinogen should be absent/reduced, not increased. Whereas in hemolytic anemia, the urobilinogen is increased, not negative

Dr. Riaz Reply
April 6, 2021

Table corrected, thanks for the comment.

Add Comment Cancel


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