pediatrics
Neonatal Hyperbilirubinemia
Etiology of Neonatal Hyperbilirubinemia
There are several ways to classify and discuss causes of hyperbilirubinemia. Because transient jaundice is common among healthy neonates (unlike adults, in whom jaundice always signifies a disorder), hyperbilirubinemia can be classified as physiologic or pathologic. It can be classified by whether the hyperbilirubinemia is unconjugated, conjugated, or both. It also can be classified by mechanism ( see Table: Causes of Neonatal Hyperbilirubinemia ). Most cases involve unconjugated hyperbilirubinemia. Some of the most common causes of neonatal jaundice include Physiologic hyperbilirubinemia Breastfeeding jaundice Breast milk jaundice Pathologic hyperbilirubinemia due to hemolytic disease Liver dysfunction (eg, caused by parenteral alimentation causing cholestasis, neonatal sepsis, neonatal hepatitis) may cause a conjugated or mixed hyperbilirubinemia. Physiologic hyperbilirubinemiaoccurs in almost all neonates. Shorter neonatal red blood cell life span increases bilirubin production, deficient conjugation due to the deficiency of uridine diphosphate-glucuronosyltransferase (UGT) decreases clearance, and low bacterial levels in the intestine combined with increased hydrolysis of conjugated bilirubin increase enterohepatic circulation. Bilirubin levels can rise up to 18 mg/dL (308 micromol/L) by 3 to 4 days of life (7 days in Asian infants) and fall thereafter. Breastfeeding jaundicedevelops in one sixth of breastfed infants during the first week of life. Breastfeeding increases enterohepatic circulation of bilirubin in some infants who have decreased milk intake and who also have dehydration or low caloric intake. The increased enterohepatic circulation also may result from reduced intestinal bacteria that convert bilirubin to nonresorbed metabolites. Breast milk jaundiceis different from breastfeeding jaundice. It develops after the first 5 to 7 days of life and peaks at about 2 weeks. It is thought to be caused by an increased concentration of beta-glucuronidase in breast milk, causing an increase in the deconjugation and reabsorption of bilirubin. Pathologic hyperbilirubinemiain term infants is diagnosed if Jaundice appears in the first 24 hours, after the first week of life, or lasts>2 weeks Total serum bilirubin rises by>5 mg/dL/day (> 86 micromol/L/day) Total serum bilirubin is>18 mg/dL (> 308 micromol/L/day) Infant shows symptoms or signs of a serious illness Some of the most common pathologic causes are Immune and nonimmune Overview of Hemolytic Anemia None Hematoma resorption Neonatal Sepsis None Hypothyroidism in Infants and Children None 