bilirubin


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bilirubin

 [bil″ĭ-roo´bin]
a yellow to orange bile pigment produced by the breakdown of heme and reduction of biliverdin; it normally circulates in plasma and is taken up by liver cells and conjugated to form bilirubin diglucuronide, the water-soluble pigment excreted in the bile.
Bilirubin. The metabolism of bilirubin. Once bile is taken up and conjugated by the liver, some leakage of bilirubin mono- and diglucuronides does occur, but these normally account for less than 5% of circulating bilirubin. In bile, more than 80% is conjugated as the diglucuronide form. From Aspinall and Taylor-Robinson, 2001.
Failure of the liver cells to excrete bile, or obstruction of the bile ducts, can cause an increased amount of bilirubin in the body fluids and lead to obstructive jaundice.

Another type of jaundice, hemolytic jaundice, results from excessive destruction of erythrocytes. The more rapid the erythrocyte destruction and hemoglobin degradation, the greater the amount of bilirubin in body fluids.

Laboratory tests for the determination of bilirubin content in the blood are of value in diagnosing liver dysfunction and in evaluating hemolytic anemias. (See accompanying table.) Bilirubin may be classified as indirect (“free” or unconjugated) while en route to the liver from its site of formation by reticuloendothelial cells, and direct (bilirubin diglucuronide) after its conjugation in the liver with glucuronic acid. Elevated indirect bilirubin levels indicate prehepatic jaundice, such as hemolytic jaundice, or certain types of hepatic jaundice involving inability to conjugate bilirubin. Elevated direct bilirubin levels indicate other types of hepatic jaundice, such as in viral or alcoholic hepatitis, or posthepatic jaundice, as in biliary obstruction.

Normally the body produces a total of about 260 mg of bilirubin per day. Almost 99 per cent of this is excreted in the feces; the remaining 1 per cent is excreted in the urine as urobilinogen.

bil·i·ru·bin

(bil'i-rū'bin),
A yellow bile pigment found as sodium bilirubinate (soluble), or as an insoluble calcium salt in gallstones; formed from hemoglobin during normal and abnormal destruction of erythrocytes by the reticuloendothelial system; a bilin with substituents on the 2, 3, 7, 8, 12, 13, 17, and 18 carbon atoms and with oxygens on carbons 1 and 19. Excess bilirubin is associated with jaundice.
[bili- + L. ruber, red]

bilirubin

/bil·i·ru·bin/ (-roo´bin) a bile pigment produced by breakdown of heme and reduction of biliverdin; it normally circulates in plasma and is taken up by liver cells and conjugated to form bilirubin diglucuronide, the water-soluble pigment excreted in bile. High concentrations of bilirubin may result in jaundice.
conjugated bilirubin , direct bilirubin bilirubin that has been taken up by the liver cells and conjugated to form the water-soluble bilirubin diglucuronide.
indirect bilirubin , unconjugated bilirubin the lipid-soluble form of bilirubin that circulates in loose association with the plasma proteins.

bilirubin

(bĭl′ĭ-ro͞o′bĭn, bĭl′ĭ-ro͞o′-)
n.
A reddish-yellow bile pigment, C33H36N4O6, derived from the degradation of heme.

bilirubin

[bil′iro̅o̅′bin]
Etymology: L, bilis + ruber, red
the orange-yellow pigment of bile, formed principally by the breakdown of hemoglobin in red blood cells after termination of their normal lifespan. Water-insoluble unconjugated bilirubin normally travels in the bloodstream to the liver, where it is converted to a water-soluble, conjugated form and excreted into the bile. In a healthy person, about 250 mg of bilirubin is produced daily. The majority of bilirubin is excreted in the stool. The characteristic yellow pallor of jaundice is caused by the accumulation of bilirubin in the blood and in the tissues of the skin. Testing for bilirubin in the blood provides information for diagnosis and evaluation of liver disease, biliary obstruction, and hemolytic anemia. Normal levels of total bilirubin are 0.1 to 1.2 mg/dl or 2 to 21 μmol/L. See also jaundice.

bilirubin

A yellow-red haemoglobin-breakdown product derived from catabolised RBCs, present in bile transported from the liver to the gallbladder to the intestines. BR gives bile its colour and is normally passed in stool; increased production or decreased excretion of BR results in cutaneous and ocular sclera jaundice. BR that has not been metabolised in the liver is termed indirect bilirubin (BRI) and is attached to albumin in the circulation; after hepatic metabolism, it is no longer bound to proteins, and is called direct bilirubin (BRD). The sum of BRD and BRI equals total bilirubin (BRT), which is usually measured as part of a routine chemistry profile and in liver profiles; if BRT is increased, the lab automatically measures BRD; BRI is a calculated value of BRT – BRD.
 
Ref range
BRT, umbilical cord <2.0 mg/dL; 0–1 day of life <6.0 mg/dL; 1–2 days <8.0 mg/dL; 3–5 days <12 mg/dL; thereafter <0.2–1.0 mg/dL; BRD < 0.3 mg/dL; BRI 0.2–1.3 mg/dL; BRT 0.3–1.6 mg/dL.

BRI is increased in liver damage, hemolytic anaemia, congenital enzyme deficiencies; BRD is increased in biliary obstruction; RT is increased in continuous hemolysis and biliary obstruction with hepatic damage.
 
Urine
Negative.
 
Amniotic fluid
28 weeks <0.075 mg/dL; 40 weeks <0.025 mg/dL.

bilirubin

BR Lab medicine A yellow-red Hb breakdown product derived from catabolized RBCs, present in bile transported from the liver to the gallbladder to the intestines; BR gives bile its color and is normally passed in stool; ↑ production or ↓ excretion of BR results in jaundice of the skin and ocular sclera; BR that has not been metabolized in the liver is indirect bilirubin–BRI, and is attached to albumin in the circulation; after hepatic metabolism, it is no longer bound to proteins, and is called direct bilirubin–BRD; the sum of BRD and BRI is total bilirubin–BRT, which is usually measured as part of a routine chemistry profile, and in liver profiles; if BRT is ↑, the laboratory automatically measures BRD; BRI is a calculated value of BRT – BRD Ref range BRT, umbilical cord <2.0 mg/dL; 0-1 day of life <6.0 mg/dL; 1-2 day <8.0 mg/dL; 3-5 day <12 mg/dL, thereafter <0.2-1.0 mg/dL; BRD < 0.3 mg/dL; BRI 0.2–1.3 mg/dL; BRT 0.3–1.6 mg/dL; BRI is ↑ in liver damage, hemolytic anemia, congenital enzyme deficiencies; BRD is ↑ in biliary obstruction; BRT is ↑ in continuous hemolysis, biliary obstruction with hepatic damage Urine Negative Amniotic fluid 28 wk <0.075 mg/dL; 40 wk <0.025 mg/dL See Conjugated bilirubin, Delta bilirubin.

bil·i·ru·bin

(bil'i-rū'bin)
A yellow bile pigment found as sodium bilirubinate (soluble),or as an insoluble calcium salt in gallstones, formed from hemoglobin during normal and abnormal destruction of erythrocytes by the reticuloendothelial system. Excess levels of bilirubin are associated with jaundice.
[bili- + L. ruber, red]

bilirubin

A coloured substance in bile derived from the breakdown of haemoglobin in effete red blood cells at the end of their 120 day life. Bilirubin is conjugated with glucuronic acid in the liver and excreted in the bile, giving the stools their characteristic colour. When it cannot escape freely into the bowel it accumulates in the blood, staining the skin to cause JAUNDICE. The stools become pale and the urine dark. Conjugated bilirubin is water-soluble.

bilirubin

a reddish-yellow BILE pigment.

Bilirubin

A pigment produced by the liver that is excreted in bile which causes a yellow discoloration of the skin and eyes when it accumulates in those organs. Bilirubin levels can be measured by blood tests, and are most often elevated in patients with liver disease or a blockage to bile flow.

bilirubin

an orange bile pigment produced by the breakdown of heme and reduction of biliverdin; it normally circulates in plasma and is taken up by liver cells and conjugated to form bilirubin diglucuronide, the water-soluble pigment excreted in the bile. Failure of the liver cells to excrete bile, or obstruction of the bile ducts, can cause an increased amount of bilirubin in the body fluids and thus lead to obstructive or regurgitation jaundice.
Another type of jaundice results from excessive destruction of erythrocytes (hemolytic or retention jaundice). The more rapid the destruction of red blood cells and the degradation of hemoglobin, the greater the amount of bilirubin in the body fluids.
Most bilirubin is excreted in the feces. A small amount is excreted in the urine as urobilinogen.

conjugated bilirubin
bilirubin that has been conjugated, mainly to glucuronic acid, in the liver and gives a direct result to the van den bergh test. High blood levels indicate obstructive or hepatocellular origin of the jaundice.
delta bilirubin
bilirubin diglucuronide
see conjugated bilirubin (above).
free bilirubin
see unconjugated bilirubin (below).
bilirubin toxicity
unconjugated bilirubin
bilirubin that has not been conjugated in the liver. It gives an indirect reaction to the van den bergh test. A high level of it in the blood is indicative of hemolysis or a lack of bilirubin clearance by the liver. Called also free bilirubin.
References in periodicals archive ?
The bilirubin market analysis is provided for both the international and Chinese domestic situations including development trends, competitive landscape analysis, key regions development status and a comparison analysis between the international and Chinese markets.
IgG and IgM paraproteins have been suggested to interfere with total bilirubin assays, especially on Roche analyzers, by forming precipitants (1-5).
A survey was also conducted showing that 13 of the 25 responding laboratories were still doing confirmatory testing for bilirubin by Ictotest (52%).
Caption: A protein in the muscles of Japanese freshwater eels (shown) glows when it meets the compound bilirubin, a breakdown product of red blood cells.
To prevent unconjugated bilirubin being deposited in tissues it is bound to albumin (a protein) and then transported in the blood to the liver where it is converted to its conjugated form by an enzyme called glucuronyltransferase (England, 2010; McIntosh and Stenson, 2008).
Bilirubin is produced during the breakdown of old blood cells.
2) In neonates, however, high levels of circulating bilirubin may have potentially severe consequences, due to bilirubin's ability to cross the blood-brain barrier and attach to developing brain tissues.
His bilirubin level was within the normal range for newborns, and his neurological development and the results of neurological examination were normal at 12 months of age.
while if bilirubin level is high, they tend to turn brown.
Usually, the liver removes bilirubin from the blood, enabling the body to excrete it in urine.
Other laboratory tests revealed acute hepatitis with AST 653 IU/L, ALT 1134 IU/L, alkaline phosphatase (ALP) 340 IU/L, total bilirubin 3.