Bilirubin is a yellow-hued compound found in the normal catabolic pathway of vertebrates and it works to break down heme. Earlier known as haematoidin, bilirubin was discovered by Rudolf Virchow, a German physician and scientist, in 1847. This catabolism is a process that is essential for eliminating waste products generated from the destruction of the old erythrocytes (red blood cells) from the body.
Basically, bilirubin is a type of yellowish pigment present in bile. This pigment imparts the characteristic yellow tint to the skin and eyes of a person suffering from jaundice. Moreover, it also occurs in the region of bruises, thereby creating the characteristic yellowish hue that is usually related to a healing bruise. A blood test will help to evaluate the concentration of bilirubin. In case a physician or healthcare professional suspects that a person is suffering from excessive bilirubin or in eliminating or processing this pigment, he can ask for a blood test as a part of diagnosis.
The process begins with the stripping the hemoglobin from the heme molecule. Subsequently, the heme goes though a number of different processes related to porphyrin catabolism, subject to the body part where the breakdown is taking place. For instance, the heme molecules found in the urine are different from the ones that are present in the stool. The first foremost phase in the catabolic pathway is biliverdin production from heme. Following this, the second step of biliverdin and bilirubin production is undertaken by the enzyme biliverdin reductase.
Bilirubin is send out to the bile and urine and high levels of this yellowish pigment in one's body may be a sign that he is suffering from specific diseases. In fact, bilirubin is the reason why our skin and eyes have a yellow tint when we suffer from jaundice. It also occurs around a wound that is healing. The products formed after the breakdown of bilirubin in subsequent steps include stercobilin, which imparts a brown hue to human feces. Urobilin is another product formed due to the breakdown of bilirubin. This straw-yellow substance is found in the urine. Urobilin is also present in many plants.
Generally, our body eliminates excessive bilirubin via urine and stool, thereby maintaining a somewhat stable and healthy level of the pigment. However, in case the body is unable to process bilirubin, it may result in a build-up of unconjugated (indirect) form of this compound. While adults develop various diseases when such a condition occurs, it can turn out to be grave in the case of newborns. This is primarily because this yellowish compound has the potential to cause brain cell damage, resulting in a number of neurological disorders. Accumulation of too much bilirubin in the body can also be one reason for developing jaundice.
Several problems can get in the way of bilirubin processing. For instance, the enzymes necessary for creating the direct or conjugated form of the pigment may be absent in the body, thereby resulting in an increase in the levels of its indirect or unconjugated form. In addition, any damage to the liver or liver ailment can also hinder the ability of the liver to process bilirubin. In fact, the weakened liver may not be capable of working at a faster pace to cope with the bilirubin production by the body. At the same time, problems may also arise due to the pigment's expression, which may lead to a build-up of conjugated bilirubin in the body and cause diseases.
Undergoing a blood test helps with information regarding the direct (conjugated) and indirect (unconjugated) forms of bilirubin present in our body. Generally, a bilirubin blood test provides a few indications, in addition to examining the levels of a number of other compounds present in the blood. Information about the type of bilirubin present in elevated levels as well as the extent of increase can help a physician or healthcare professional to begin exploring the reasons responsible for the conditions suffered by a patient. Moreover, it also helps the physician to choose the correct treatment for the malaise. If the levels of bilirubin are perilously elevated, physicians may opt for emergency treatment to get rid of the surplus pigment present in the blood, thereby restoring normalcy. Once the level of bilirubin has been stabilized, doctors can work on developing a treatment map to ensure that the problem does not occur again.
The standard direct bilirubin level in adults or older children varies between 0 mg/ deciliter (mg/dL) and 0.4 mg/dL. The usual levels of total (direct and indirect) bilirubin range between 0.3 mg/dL to 1.0 mg/dL.
On the other hand, elevated levels of bilirubin are somewhat normal in newborns and it occurs owing to stress caused during birth. The standard bilirubin level in a newborn is below 5 mg/dL. However, it has been found that many newborns suffer from jaundice and, in such cases their total bilirubin levels are often higher than 5 mg/dL.
In case it is found that the bilirubin level in your body is significantly high, it is likely that your physician would want you to undergo blood tests or even an ultrasound examination. There are several reasons for the levels to be high in your blood. In the case of adults, it may occur owing to problems related to the liver, gallbladder or the bile duct. Some of the conditions that may lead to high levels of this pigment in the body include drug toxicity, gallstones, liver ailments like hepatitis, liver cirrhosis or scarring in the liver, a genetic disease called Gilbert's disease and cancer of the pancreas or the gallbladder. In addition, biliary stricture, wherein a portion of the bile duct constricts too much obstructing fluid passage may also cause the bilirubin levels to rise.
Bilirubin tests are undertaken to identify if the levels of this pigment are high in the blood stream. These tests may also be undertaken to find the reasons responsible for jaundice. Bilirubin test is also use to determine if one is suffering from hemolytic anemia, liver ailments and/ or bile duct obstruction.
This yellow pigment is actually a waste product that is mainly produced during the process involving the normal heme breakdown. A constituent of hemoglobin, heme is present in the red blood cells (erythrocytes). In the end, the liver processes bilirubin, thereby making it easier for the body to get rid of this yellowish pigment. However, when the breakdown of red blood cells is sped up or there is an effect on the processing as well as elimination of this pigment from the body owing to any health condition, it results in an elevated level of bilirubin in the blood stream.
The level of two types of bilirubin - conjugated (direct) and unconjugated (indirect) - can be measured or evaluated by undertaking tests in the laboratory.
Unconjugated or indirect bilirubin: Hemoglobin releases heme, which is subsequently changed to unconjugated bilirubin. Proteins transport this form of the yellow pigment to the liver. Very little amounts of unconjugated bilirubin may also be found in the blood stream.
Conjugated or direct bilirubin: This form of the yellow pigment forms inside the liver as a result of sugars binding (conjugating) to bilirubin. Subsequently, conjugated bilirubin gets into the bile and moves to the small intestines via the liver. Finally, it is eliminated from the body with stool. Generally, the blood does not contain any trace of conjugated bilirubin.
Generally, a chemical test is undertaken to measure the level of total bilirubin (conjugated as well as unconjugated) in the blood. If it is found that the total level of bilirubin is elevated, the laboratory can undertake another chemical test to determine the forms of bilirubin that are soluble in water. The water soluble form for this yellowish pigment is also known as "direct" bilirubin. Such chemical tests present an approximation regarding the quantity or level of conjugated bilirubin present in the body. When you subtract this amount from the total level of bilirubin it helps to get estimation about the amount of "indirect" unconjugated level of the pigment in the body. The findings of bilirubin tests help the healthcare providers to get information about the patient's health and plan their treatment accordingly.
Bilirubin plays an important role in diagnosing various health conditions. In fact, the level of bilirubin is measured in adults as well as grown up children to diagnose and also monitor diseases related to the liver and the bile duct, such as hepatitis, gallstones and cirrhosis of the liver. It is also measured to appraise the health of people suffering from sickle cell disease or the various causes related to hemolytic anemia. Such people may suffer from incidences known as crises owing to destruction of red blood cells (RBC), which results in an increased level of bilirubin.
Bilirubin is also used to determine the reasons for jaundice in newborns suffering from this disease. The level of only indirect or unconjugated bilirubin is increased in newborns suffering from physiologic jaundice as well as hemolytic disease.
While the above mentioned cases are quite common, in exceptional cases wherein a newborn's liver is damaged owing to biliary atresia and neonatal hepatitis it will also augment the concentration of conjugated or direct bilirubin. Therefore, when the concentration of conjugated bilirubin is increased it is often considered to be the first proof of the fact that the baby may be suffering from any of these two health conditions.
It is important to measure the bilirubin concentration in a newborn. This will facilitate to identify as well as treat the disease the infant may be suffering at an early stage. If this goes untreated, too much unconjugated or indirect bilirubin may harm the newborn's developing brain. As a result of this kind of brain damage, the newborn may suffer from hearing loss, learning as well as developmental disabilities, mental retardation, problems in eye movements and even death.