There is a broad differential diagnosis for conjugated hyperbilirubinemia in the newborn period. If the patient appears
sick, the differential diagnosis includes sepsis, galactosemia,
and hypopituitarism. If the patient appears well, obstructive, infectious, and metabolic etiologies should be considered.
Obstructive conditions include extrahepatic biliary
atresia, choledochal cyst, idiopathic neonatal hepatitis,
Alagille syndrome, gallstone, and cystic fibrosis.
Biliary atresia must be evaluated with a liver ultrasound and liver biopsy quickly as long-term outcomes are better for infants who
undergo a Kasai procedure at age less than 60 days.
Infants with biliary atresia typically are feeding and growing well and subsequently develop clay-colored stools as the bile flow
decreases.
The abdominal ultrasound is also helpful in diagnosing other causes of cholestasis including a choledochal cyst or gallstones.
Alagille syndrome is a genetic disorder with symptoms that include conjugated hyperbilirubinemia due to a lack of bile ducts, peripheral pulmonary stenosis, butterfly vertebrae, triangular facies, and eye abnormalities (posterior embryotoxon). Cystic fibrosis can also cause neonatal cholestasis.
Infectious causes of conjugated hyperbilirubinemia include
TORCHinfections, most commonly cytomegalovirus, urinary
tract infections, and sepsis due to Gram-negative bacteria.
Head ultrasound and eye examination are useful in identifying
TORCH infections.
There are many metabolic causes of conjugated hyperbilirubinemia including galactosemia and tyrosinemia, which are tested for on the newborn screen.
Urine reducing substances and succinylacetone are positive
in patients with galactosemia and tyrosinemia, respectively.
Hypothyroidism and panhypopituitarism can also lead to
cholestasis and can be diagnosed with appropriate hormonal
studies.
Alpha-1-antitrypsin (A1AT) deficiency leads to accumulation of A1AT in the hepatocytes, which leads to abnormal bile secretion and cholestasis. Total parenteral nutrition and medication use are other important causes of cholestasis.
Medications that more commonly lead to conjugated hyperbilirubinemia include amoxicillinclavulanate, trimethoprimsulfamethoxazole, erythromycin, naproxen, and rifampin.
An infant with conjugated hyperbilirubinemia who otherwise
appears well should have a laboratory evaluation, which should include a basicmetabolic panel, AST, ALT,GGT, CBC with differential, ammonia, albumin, and coagulation studies.
AST, ALT, and GGT levels are often elevated with
cholestasis due to liver cell or bile duct injury.
The GGT level is normal or low in patients with bile acid synthesis defects and progressive familial intrahepatic cholestasis (PFIC).
Prolonged prothrombin time, low albumin, and elevated ammonia
can be seen with cholestasis if there is advanced liver
injury.
The newborn screening test results should be confirmed to be normal to rule out galactosemia and tyrosinemia.
Urine should be sent for urinalysis, urine culture and sensitivity,
and reducing substances to look for urinary tract infection
and galactosemia.
An abdominal ultrasound should be performed early in the evaluation process to assess for biliary atresia, choledochal cyst, or other anatomic causes for cholestasis.
While awaiting the test results, the parents should be counseled to have their infant evaluated if he develops fever, acholic stools, worsening jaundice, or easy bleeding.
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