Jaundice Flashcards
Jaundice?
yellow/green appearance to the skin & eyes (Icterus) produced by increased serum bilirubin
- Usually given in a direct/total relationship
Normal bilirubin ranges?
- ranges 0.5 to 1.0 mg/dl.
- Levels >3.0 mg/dl to be clinically jaundiced
N.B. the Newborn period is the exception
Describe bilirubin metabolism?
- Red cells (Heme) break down forming biliverdin (bile pigment)
- This is unconjugated (indirect bilirubin). - It is transported by albumin & is not soluble - No Bilirubin in the urine
- The bile pigment is converted to conjugated (Direct bilirubin) by the Kupffer cells of the liver.
- In the liver, the bilirubin is conjugated
with UDPglucuronate, making it water-soluble Bilirubin diglucuronide
i.e. (“direct” conjugated bilirubin).
- This is soluble & only shows up in blood & urine with obstruction in the system
Describe Bilirubin conjugation?
- In the terminal ileum the bilirubin is converted to stercobilinogen & urobilinogen by natural bacteria
- Conjugated bilirubin is excreted into the bile and passed into the intestine where it is further metabolised
- urobilinogen ->urobilin-> stercobilin, which colors the feces brown
- Some is reabsorbed and returned to the liver - Some urobilinogen is found in the urine
- If excretion of conjugated bilirubin is hindered, it is excreted by the kidney
Causes of Pre-hepatic jaundice?
hemolytic disease
Causes of Post-hepatic jaundice?
- Hepatitis
- Drug induced hepatitis
- Cirrhosis
Causes of Obstructive jaundice?
- gallstones
- pancreatic cholangio carcinoma
- liver fluke - schistosomiasis
Consequences of obstructive jaundice?
- Obstruction of biliary system prevents production of urobiligen & stercobilinogen
- Stool is light and urine is dark showing bilirubin
Classification of hyperbilirubinemia?
- Increased bilirubin production
- Decreased bilirubin uptake by the liver
- Impaired conjugation in the liver
- unconjugated (indirect) = normal stool and urine color - Decreased excretion of bilirubin into the bile (cholestasis)
- conjugated bilirubin (direct) with dark urine and light stool color
Causes of unconjugated (indirect) hyperbilirubinemia?
- Due to overproduction
- decreased hepatic uptake
- decreased conjugation of bilirubin
Causes of over production of unconjugated bilirubin?
- secondary to hemolysis (autoimmune)
- ineffective erythropoiesis (megablastic anemia)
- increase RBC fragility/turnover (2,3 DPG deficiency)
Causes of impaired hepatic uptake of UB leading to hyperbilirubinemia?
- Gilbert’s syndrome
- certain drugs such as rifampin, anesthetics & radiographic dyes
Causes of impaired conjugation that lead to UB hyperbilirubunemia?
- Hepatocellular disease
- drug inhibition such as chloramphenicol, anabolic steroids
- genetic disorders such as Gilbert’s syndrome or Crigler- Najjar syndrome (decreased UDP-glucuronyl transferases).
What is the most common cause of jaundice?
neonatal jaundice
What makes newborns susceptible to having jaundice?
They do not have a significant quantity of glucouronyl transferase (the enzyme used for conjugation), due to enzyme immaturity, but kicks in within a few weeks