Bilirubin

"A slight increase in indirect bilirubin appears very frequently in the population without major pathological significance".

DR. JOSÉ IGNACIO MONREAL MARQUIEGUI
SPECIALIST. BIOCHEMISTRY DEPARTMENT

Bilirubin is a waste product from the metabolism of hemoglobin. Old, defective or damaged red blood cells are removed by phagocytic cells (macrophages). Within these cells, hemoglobin is metabolized and heme is transformed into bilirubin, which is released into the blood. This bilirubin is not very soluble in water and for its transport in the blood it is linked to albumin.

Once it reaches the liver, this bilirubin is captured and binds to glucuronic acid, so the bilirubin becomes more soluble. Then, it goes to the intestine. Intestinal bacteria metabolize this bilirubin and transform it into a series of pigments (urobilinogens) that give the stool its typical yellow-brown color. Some of these urobilinogens, since they are more soluble in water, are reabsorbed into the blood and are eliminated by the kidneys in the urine.

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When is bilirubin testing indicated?

Total and direct bilirubin is chemically determined in the serum and the indirect is calculated by difference. A total bilirubin concentration of less than 1.2 mg/dl is normal and most is indirect bilirubin. In normal individuals, bilirubin should not appear in the urine.

When there is an elevation of direct bilirubin in blood, then it can be filtered by the kidney and appears in urine, so that it can take on an orange color.

The presence of bilirubin and urobilinogen in urine can be easily detected qualitatively using test strips.

Most frequent indications of this test:

  • Liver cirrhosis
  • Viral Hepatitis
  • Hepatocarcinoma
  • Liver toxicity

Do you have any of these diseases?

You may need to be tested for bilirubin

Types of Bilirubin Analysis

  • Direct or conjugated bilirubin: is bilirubin bound to glucuronic acid. It is hydrosoluble. It is eliminated through urine.
  • Indirect bilirubin, free or not conjugated: it comprises the bilirubin joined to the albumin. It is liposoluble. It is not eliminated by the urine.

An increased concentration of total bilirubin in the blood leads to a situation called jaundice.

Jaundice can be defined as a yellow-green discoloration of the skin and mucous membranes by an accumulation of bilirubin.

Basically, jaundice can be classified into 3 groups.

  • Prehepatic jaundice. For example, that produced by a hemolysis (massive destruction of red blood cells). The increase in the rupture of red blood cells produces an unconjugated hyperbilirubinemia superior to the capacity of the liver to purify. It will increase indirect bilirubin in the blood and direct bilirubin will be practically normal. In urine, urobilinogen will increase and bilirubin will not be detected, since unconjugated bilirubin, being strongly bound to albumin, does not filter through the kidney into the urine.
  • Posthepatic jaundice. Due to an extrahepatic obstruction such as choledocholithiasis. The obstruction causes conjugated bilirubin to return to the blood and not pass into the intestine. Hyperbilirubinemia will be mainly direct, so there will also be an increase in bilirubin in the urine. When little bilirubin is eliminated into the intestine, very little urobilinogen is formed, so the faeces will be pale. Once the obstruction is removed, the stool must regain its color and the urine must be positive for urobilinogen.
  • Hepatic jaundice. It is an intermediate state between the two previous ones. It may be due to toxins or infections such as viral hepatitis. It will increase the direct and indirect bilirubin in blood. In urine will raise bilirubin and urobilinogen will be little increased or even decreased.

Where do we do it?

IN NAVARRE AND MADRID

The Clinical Biochemistry Service
of the Clínica Universidad de Navarra

The Clinical Biochemistry Service of the Clinica Universidad de Navarra is responsible for performing the biochemical analyses requested by the medical specialists of our center.

We carry out technical quality controls to guarantee the proper functioning of the equipment and the highest precision in the results obtained from the samples.

In order to guarantee excellence in patient service, we offer the response with the results of the analyses in the shortest possible time, responding in only 46 minutes in some cases of general analysis.

Organized in care units

  • General biochemistry.
  • Electrolytes.
  • Hormones, urine and proteins.
  • Markers.
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Why at the Clinica?

  • Maximum speed in offering the analytical results.
  • We carry out quality controls to guarantee the correct and most precise results obtained.
  • We work in a multidisciplinary way with all the departments of the Clinic.

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