Bilirubin: What It Is and Why It Matters

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When red blood cells become old or damaged, they are broken down by the liver. During this process, a substance called bilirubin is produced. A brownish yellow substance contained in bile, bilirubin is normally excreted from the body through the process of defecation, and pigments stool to give it its normal brown color. 

Causes of Elevated Bilirubin

Compromised liver function from diseases such as hepatitis.

and obstructions in the bile ducts (passageways) through which bile passes from the liver to the small intestine are two of the primary conditions that cause elevated bilirubin levels in the bloodstream. In addition, certain blood disorders such as hemolytic anemia, can cause elevated bilirubin levels.

When the process by which bilirubin is excreted is compromised by any condition or disease, bilirubin levels increase in the bloodstream and can cause a characteristic set of signs and symptoms known as jaundice. Jaundice can cause:

  • Yellowing of the skin and whites of the eyes 
  • Urine that is darker than usual
  • Stools that are pale in color

More Information on Jaundice

Tests to Detect Elevated Bilirubin

Bilirubin in the bloodstream exists in two forms:

  • Unconjugated, or indirect, bilirubin: Does not dissolve in water and travels through the bloodstream to the liver, where it is changed into a soluble form.
  • Conjugated, or direct: Prodced by the liver from indirect bilirubin, this form is soluble.

When a physician orders tests to measure the health of the liver, a bilirubin test is almost always included. A blood test can measure both total bilirubin and direct bilirubin levels, and indirect bilirubin levels can be inferred from the total and direct bilirubin measurements.

Normal Bilirubin Levels

Although different labs use different reference ranges, generally, for older children and adults, the following ranges indicate normal bilirubin levels:

Conjugated (direct) bilirubin: 0 to 0.3 mg/dL (milligrams per deciliter). 

Total bilirubin (direct and indirect combined): are from 0.3 to 1.2 mg/dL.

Next Steps

If bilirubin levels are elevated, a physician will want to determine the cause. In many cases, imaging of the abdomen is performed either through ultrasonography, computed tomography (CT) scans, or magnetic resonance imaging (MRI). 

I an ultrasound shows there is a bile duct blockage, other tests may be ordered to determine the cause. In some cases, a liver biopsy will be needed, for example when certain conditions, including hepatitis, are suspected or when physicians are struggling to reach a diagnosis. 

Once an underlying cause has been found and a diagnosis has been reached, treatments will be aimed at addressing that disease or condition. For example, if acute viral hepatitis is causing jaundice, it may resolve gradually on its own without treatment.

But if chronic hepatitis is the cause, even if jaundice disappears, various other treatments may be considered. If the cause is a bile duct blockage, a procedure to open the bile duct may be performed, usually endoscopically, using minimally invasive techniques. 

The important thing to remember about elevated bilirubin levels are that they are a sign of disease, and not a disease in themselves. Further exploration is almost always warranted, and your physician should be focused on finding the underlying condition.

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