Pediatric emergency medicine trisk 0872 0872
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CHAPTER 44 ■ JAUNDICE: CONJUGATED
HYPERBILIRUBINEMIA
ERIN B. HENKEL, SANJIV HARPAVAT
INTRODUCTION
The pediatric emergency provider is typically confronted with the finding of
hyperbilirubinemia in one of two situations: (1) a jaundiced child, or (2) an
incidental finding during a laboratory evaluation. When conjugated
hyperbilirubinemia is found, the challenge lies in determining if it is a sign of a
life-threatening condition.
NORMAL BILIRUBIN PHYSIOLOGY
Senescent red blood cells release heme which is eventually converted to
unconjugated bilirubin. Unconjugated bilirubin then binds to albumin and is
transported to the liver. In the liver sinusoids, unconjugated bilirubin detaches
from albumin and gains entry into the hepatocyte, where it is conjugated with
glucuronide by the action of uridine diphosphate glucuronyl transferase. The
soluble conjugated diglucuronide then is secreted out of the hepatocyte, across its
canalicular membrane into the bile. Conjugated bilirubin, along with bile salts,
phospholipids, cholesterol, and metabolites are the major constituents of bile. Bile
flows through the intrahepatic biliary tree, into the extrahepatic bile ducts
(including the common bile duct), and finally into the intestine at the ampulla of
Vater. In the intestine, bacterial flora converts bilirubin to urobilinogen. Some
urobilinogen is reabsorbed and taken up by the liver cells, only to be reexcreted
into the bile. A small percentage of urobilinogen escapes into the systemic
circulation and is excreted in the urine. The unabsorbed urobilinogen is excreted
in the stool as fecal urobilinogen (see Chapter 45 Jaundice: Unconjugated
Hyperbilirubinemia ).
DEFINITION
The definition of conjugated hyperbilirubinemia has evolved in recent years.
Most recently it has been redefined as a conjugated bilirubin level >1 mg/dL (or
>17 mmol/dL) after 2 weeks of life (2017 NASPGHAN Guidelines). From the
perspective of an emergency physician, following this definition will decrease the
risk of missing diagnoses. Cholestatic jaundice is always considered pathologic
and warrants further evaluation for hepatobiliary dysfunction.
