Why am I Yellow? Flashcards
What is the basic metabolism of bilirubin in the liver?
import across basolateral membrane, conjugation, secretion across apical membrane
What are the basic mechanisms behind unconjugated hyperbilirubinemia?
increased input (hemolysis) or decreased output into bile (conjugation defect)
What are the basic mechanisms behind unconjugated + conjugated hyperbilirubinemia?
normal input and decreased output (transporter/excretion defect) or increased back flux of bilirubin
What is the pre-hepatic mechanism of isolated hyperbilirubinemia?
hemolysis
normal reserve capacity of liver for bilirubin is 7-fold
unconjugated increases and conjugated does not
isolated if no associated liver disease
What is the hepatic mechanism of hepatic hyperbilirubinemia?
no associated liver or biliary disease
decreased hepatic conjugation
mild genetic defects (gilberts) are common
What are more severe conditions associated with hepatic isolated hyperbilirubinemia?
excretion defects (Crigler Najjar and Dubin-Johnson) - rare
What happens in sepsis that causes hyperbilirubinemia?
cytokines alter expression of organic anion transporters for conjugated bilirubin - increase in conjugated transported into circulation with little or no liver inflammation
What tests can help determine if hyperbilirubinemia is unconjugated or mixed?
bilirubin fractionation
bilirubin in urine - positive if conjugated elevated and kidney function normal
What is the treatment for isolated hyperbilirubinemia?
usually benign
UV light for newborns
transplant for rare patient with severe conjugation defect
How can Gilbert’s be recognized?
males>females
AD inheritance
serum bilirubin <3-5 mg/dL, increases with fasting and stress
What are some exogenous agents causing hepatocyte injury and which have highest aminotransferases (>500)?
viruses*, bacteria, protozoa, helminths *prescription and non-Rx remedies metals (iron and copper) *toxins alcohol
What are some endogenous agents causing hepatocyte injury and which have the highest aminotransferases (>500)?
*ischemia fat bile and *biliary obstruction abnormal misfolded proteins *Host T lymphocytes
How do the measured enzymes differ between necrosis and apoptosis?
aminotransferases raised preferentially in apoptosis
all enzymes released in necrosis
What signs and symptoms suggest ischemia induced hepatitis?
dyspnea, edema, cocaine use, summer
heart failure, hypotension, hyperthermia
What signs and symptoms suggest obstruction induced hepatitis?
RUQ pain and tenderness
