Approach to Icterus

Question 1

list the three broad categories for causes of icterus/hyperbilirubinemia

Answer 1

1. Prehepatic: macrophages and monocytes breaking down more RBC’s than normal
2. Hepatic: Not processing the bilirubin/can’t conjugate from insoluble to soluble
3. Post Hepatic: Can’t get from the bile to gut -> some type of obstruction not sending it out

Question 2

Briefly describe the physiology of bilirubin

Answer 2

Overall bilirubin a breakdown product of hemoglobin.

1. Old RBC’s stripped
2. Macros and monos convert to iron and biliverdin
3. Macros reduce biliverdin into un-conjugated bilirubin
4. Liver conjugates bilirubin to form soluble bilirubin
5. Soluble bilirubin is excrete in duodenum and bile

Question 3

common causes of pre hepatic hyperbilirubinemia

Answer 3

Immune mediated disease, Toxins (Zinc, onions, garlic), post transfusion (common transiently)

Question 4

common causes of hepatic hyperbilirubinemia

Answer 4

Toxicity (xylitol, blue/green algae), Hepatitis (sago palm), Cirrhosis, portosystemic shunts , microvascular dysplasia, secondary injury (hepatic lipidosis), Congenital deficiencies (copper storage)

Question 5

common cause of post hepatic hyperbilirubinemia

Answer 5

AKA biliary obstruction caused by a gall bladder mucocele, cholelithiasis, pancreatitis, or tumors

Question 6

yellow pale gums/mm

Answer 6

pre-hepatic because thinking hemolytic -> look at the blood smear for spherocytes

Question 7

orange gums/mm

Answer 7

think hepatic or post hepatic

Question 8

what liver function tests can you perform on an icteric patient?

Answer 8

1. Bile acids: bilirubin will interfere if theres hyperbilirubinemia
2. Ammonia quantification in blood
3. pseudofunction analytes (BUN, glucose, albumin, cholesterol): these are not produced by the liver but if you see them all decrease it may imply decreased liver function.
4. Liver enzyme elevations (ALT and ALP)

Question 9

hyperbilirubinemia with normal liver enzymes

Answer 9

pre hepatic

Question 10

elevated liver enzymes with hyperbilirubinemia

Answer 10

hepatic or post hepatic

Question 11

ALT through the roof with hyperbilirubinemia

Answer 11

hepatic

Question 12

low ALT and AST with hyperbilirubinemia

Answer 12

end stage liver failure because ALT comes from the hepatocytes as leakage enzymes but the hepatocytes aren’t there to leak it out so the enzyme levels are low

Question 13

ALT and AST are liver enzymes linked to what?

Answer 13

hepatocellular injury, ALT and AST are leakage enzymes

Question 14

If liver enzymes are increased its most likely a __ hepatic primary disease where ALP and GGT may be proportionally __ than ALT and AST

Answer 14

If liver enzymes are increased its most likely a post hepatic primary disease where ALP and GGT may be proportionally higher than ALT and AST

Question 15

when observing an ultrasound of a mucocele, how can you tell if its the cause of hyperbilirubinemia?

Answer 15

look for common bile duct distension

Question 16

how much hyperbilirubinemia is needed to see icterus?

Answer 16

2.5- 3

Question 17

how long does it take bilirubinemia to resolve?

Answer 17

The patient may have improved signs but still be yellow for awhile. The unconjugated bilirubin goes to the tissues and had to go to the blood then to urine or bile to get out of the body so it takes awhile