Explain the Bile pigments and salts in urine

The bile pigment, bilirubin (a pigment formed from the destruction of red blood cells), is altered in the intestine to urobilinogen, a coloured substance formed in the intestine from the breakdown of bilirubin. In the urine, the urobilinogen gradually changes to urobilin. In haemolytic jaundice (jaundice due to the breakdown of red blood cells), excretion of urobilin, a brown bile pigment, is increased upto 10 mg daily and in obstructive jaundice (jaundice caused by something blocking the bile duct, for example, gallstones and tumors), it is reduced usually to less than 0.3 mg daily. Bilirubin appears in the urine when there is an appreciable amount of conjugated bilirubin present in the plasma.