RBC consumed by Mphage in the RES, protopropyrin converted to UBR and carried by albumin to liver for conjugation to form CBR. Enzyme in the liver called UGT in hepatocytes conjugates the BR which is transported to bile canaliculi to form part of bile and store in the gall bladder.
Insoluble UBR is held by the albumin floating in the serum. It does not get excreted in the kidney as it is not soluble.
Bile is released into the small intestine to aid in digestion (especially fat)
Intestine flora converts CBR to urobilinogen and later oxidized to Urobilin=Sterobilin(brown) to make the stool brown.
Some of urobilinogen is absorbed to blood, some go back to liver, some goes to kidney, and converted to a yellow pigment (urobilin) in urine at the kidney,
Terminology and Presentation of Cholestasis
Cholestasis: blockage of bile flow (whether intrahepatic or extrahepatic) and hence lead to an elevation of conjugated bilirubin in blood.
Clinical findings of Cholestasis: jaundice, dark urine, pale stool, pruritis (bile salt deposit in skin)
Labs in cholestasis: elevated alkaline phosphatase (ALKP), elevated cholesterol (due to impaired excretion) skin xanthoma.
Malabsorption of fat and fat soluble vitamins (steatorrhea)
Etiology and Association:
Unconjugated Bilirubinemia (Increase UBR)
Increase RBC turnover
Physiological jaundice (newborn babies) coz liver not well develop yet
Reduce uptake from liver Hereditary – (Gilbert and Crigler-Najjar Syndrome)
Hepatitis, Cirrhosis hence interfere with conjugation of BR
Drugs (sulfonamide, PCN, rifampin, radiocontrast)
Conjugated Bilirubinemia (Increased CBR)
Cirrhosis (late stage = problem with excretion and conjugation)
Decrease intrahepatic excretion
Liver disease (cirrhosis, hepatitis)
Inherited disorder (Dubin-Johnson = canaliculi transport protein defect); (Rotor Syndrome-same but no darkening/blackening of liver)
Primary/Secondary Biliary Cirrhosis, PSC
Drug induced (OCP)
Extrahepatic biliary obstruction
Gall stone, Tumor (pancreatic, liver, cholangiocarcinoma),