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Bilirubin is essentially a waste product, formed when haemoglobin is broken down. It is not soluble in water and is carried to the liver bound onto albumin. Bilirubin is made water soluble in the liver by conjugation with glucuronic acid . As part of bile, the soluble bilirubin then passes through the common bile duct and is either temporarily stored in the gallbladder or passes right away into the gut. Some of the excreted bilirubin may be reabsorbed (entero-hepatic circulation). Bacteria in the intestines modify bilirubin, causing the brown color of feces. The yellow colour of urine is a result of products derived from bilirubin. The name of this metabolite is urobilinogen .
In diseases where too much haemoglobin is broken down or the removal of bilirubin does not function properly, the accumulating bilirubin in the body causes jaundiceJaundice technically known as icterus is yellowing of the skin, sclera (eyes) and mucous membranes caused by increased levels of bilirubin in the system. Usually the concentration of bilirubin in the blood must exceed 2-3mg/dL for the coloration to be eas.
Bilirubin is found in blood either unbound to albumin ("direct") or in the soluble, bound to albumin, form ("indirect"). The terms "direct" and "indirect" refer to the fact that soluble bilirubin can be measured directly, whereas insoluble, or indirect, bilirubin must be solubilised before measurement. Bilirubin is broken down by light, so blood tubes (especially serum tubes) should be protected from such exposure.
Although both direct and indirect bilirubin can be measured separately, it is more common to just measure total bilirubin. When we try to further elucidate the causes of jaundice or increased bilirubin it is usually simpler to look at other liver function testsLiver function tests (LFTs or LFs), are groups of clinical biochemistry laboratory blood assays designed to give a doctor or other health professional information about the state of a patient's liver. Most liver diseases cause only mild symptoms initially (especially the enzymes ALTAlanine transaminase or ALT is (mostly) a liver enzyme. It is also called Serum Glutamic Pyruvic Transaminase SGPT or Alanine aminotransferrase ALAT The spillover of this enzyme into blood is routinely measured as a marker of liver-cell damage. This helps, ASTAspartate transaminase AST also called Serum Glutamic Oxaloacetic Transaminase SGOT or aspartate aminotransferase ASAT is similar to Alanine transaminase (ALT) in that it is another enzyme associated with liver parenchymal cells. It is raised in acute liv, GGT, Alk PhosAlkaline phosphatase ALP is a hydrolase enzyme responsible for removing phosphate groups in the 5- and 3- positions from many types of molecules, including nucleotides, proteins, and alkaloids. The process of removing the phosphate group is called dephosp), blood filmmicroscopic view of an abnormal blood film. A blood film or peripheral blood smear is a slide made from a drop of blood, that allows the cells to be examined. Blood films are usually done to investigate hematological problems (disorders of the blood itsel examination ( haemolysis etc.) or evidence of infective hepatitis (e.g. Hepatitis A, B, C, delta E etc).
Bilirubin is basically an excretion product and the body does not control levels. Bilirubin levels reflect the balance between production and excretion. Thus strictly speaking there is not a normal level of bilirubin.
The reference range for total bilirubin is 2 - 14 μmol/L. For direct bilirubin, it is 0 - 4 μmol/L.
Mild rises in bilirubin may be caused by:
Moderate rise in bilirubin may be caused by:
Very High levels of bilirubin may be caused by: