chapter2:approach to patient
The bilirubin present in serum represents a balance between input
from production of bilirubin and hepatic/biliary removal of the
pigment. Hyperbilirubinemia may result from (1) overproduction
of bilirubin; (2) impaired uptake, conjugation, or excretion
of bilirubin; or (3) regurgitation of unconjugated or conjugated
bilirubin from damaged hepatocytes or bile ducts. An increase
in unconjugated bilirubin in serum results from either overproduction,
impairment of uptake, or conjugation of bilirubin. An
increase in conjugated bilirubin is due to decreased excretion into
the bile ductules or backward leakage of the pigment. The initial
steps in evaluating the patient with jaundice are to determine
(1) whether the hyperbilirubinemia is predominantly conjugated
or unconjugated in nature, and (2) whether other biochemical
liver tests are abnormal. The thoughtful interpretation of limited
data will allow for a rational evaluation of the patient
This discussion will focus solely on the evaluation of the adult
patient with jaundice.
ISOLATED ELEVATION OF SERUM BILIRUBIN
Unconjugated Hyperbilirubinemia The differential diagnosis
of an isolated unconjugated hyperbilirubinemia is limited
( Table 42-1 ). The critical determination is whether the patient
is suffering from a hemolytic process resulting in an overproduction
of bilirubin (hemolytic disorders and ineffective
erythropoiesis) or from impaired hepatic uptake/conjugation
of bilirubin (drug effect or genetic disorders).
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