Editing Bilirubin (section)

==== Conjugated ====
In the liver, bilirubin is conjugated with [[glucuronic acid]] by the enzyme [[glucuronyltransferase]], first to [[bilirubin glucuronide]] and then to [[bilirubin diglucuronide]], making it soluble in water: the conjugated version is the main form of bilirubin present in the "direct" bilirubin fraction. Much of it goes into the bile and thus out into the small intestine. Though most [[bile acid]] is reabsorbed in the [[terminal ileum]] to participate in [[enterohepatic circulation]], conjugated bilirubin is not absorbed and instead passes into the [[Large intestine|colon]].<ref name="handbook">{{cite book |title=Oxford American Handbook of Gastroenterology and Hepatology |vauthors=Cheifetz AS |publisher=Oxford University Press, USA |year=2010 |isbn=978-0199830121 |location=Oxford |page=165}}</ref>

There, colonic bacteria deconjugate and metabolize the bilirubin into colorless [[urobilinogen]], which can be oxidized to form [[urobilin]] and [[stercobilin]]. Urobilin is excreted by the kidneys to give urine its yellow color and stercobilin is excreted in the feces giving stool its characteristic brown color. A trace (~1%) of the urobilinogen is reabsorbed into the [[enterohepatic circulation]] to be re-excreted in the bile.<ref>{{cite book |last=Kuntz |first=Erwin |title=Hepatology: Textbook and Atlas |publisher=Springer |year=2008 |isbn=978-3-540-76838-8 |location=Germany |page=38}}</ref>

Conjugated bilirubin's half-life is shorter than delta bilirubin.<ref name="Sullivan Gourley 2011 pp. 176–186.e3">{{cite book |title=Pediatric Gastrointestinal and Liver Disease |vauthors=Sullivan KM, Gourley GR |publisher=Elsevier |year=2011 |isbn=978-1-4377-0774-8 |pages=176–186.e3 |chapter=Jaundice |doi=10.1016/b978-1-4377-0774-8.10017-x}}</ref>