Bile Pigments

Bile Pigments, The bile pigments are formed by the decomposition of the porphyrin ring and contain a chain of four pyrrole rings. Bilirubin, for example, the brownish-yellow pigment that gives feces its characteristic color, is the end product of the breakdown of heme from destroyed red blood cells. 

• Bilirubin: Unconjugated:
• Indicator: water insoluble
• Bilirubin: Conjugated
• Direct: Water-soluble 

Types of Bile Pigments

1. Bilirubin:

   • Formation: Bilirubin is formed from the breakdown of heme by macrophages in the spleen and liver. The heme is first converted into biliverdin, which is then reduced to bilirubin.
   • Transport: Bilirubin is transported in the blood to the liver, where it is conjugated with glucuronic acid to form bilirubin diglucuronide. This conjugated form is more water-soluble.
   • Excretion: Conjugated bilirubin is secreted into the bile and stored in the gallbladder. It is eventually released into the small intestine, where it is further broken down by bacteria into urobilinogen and stercobilinogen. These are excreted in the feces, giving stool its characteristic brown color, while some urobilinogen is reabsorbed and excreted in the urine, giving it a yellow color.

2. Biliverdin:

   • Formation: Biliverdin is an intermediate product in the breakdown of heme. It is green in color and is rapidly converted to bilirubin in most mammals.
   • Role: While biliverdin is present in small amounts in the body, it plays a more prominent role in some animals and is less commonly measured in clinical settings compared to bilirubin.

Fouchet’s Test:

Principle:

Bile pigments absorbed on ppt of Basoy. Ferric chloride in Fouchet’s reagent oxidizes bilirubin into green biliverdin.

Interference:

Bile Pigments Present.

Procedure:

Take 5ml of urine + 1ml MgSoy +2ml 10%.
Backe Filter and the precipitate few drops of Fouchet’s reagents.

Observation:

The color changes from yellow to Pista green.

Interpretation: Hay’s Sulphur test/Fouchel’s Test: