Definition And Pathophysiology

Conjugated/direct hyperbilirubinemia >1 mg/dL if total bilirubin <5 mg/dL, or >20% of total bilirubin if total >5 mg/dL.
Indicates decrease in bile formation or flow.
Always pathologic in neonatal period; mandates prompt differentiation.

Hepatocellular cholestasis: Reduced bile formation secondary to sepsis, metabolic defects, or toxins.
Obstructive cholestasis: Anatomic or functional obstruction of intrahepatic or extrahepatic biliary system.
Immature neonatal hepatic function increases susceptibility to cholestasis.
Accumulation of substances normally excreted in bile occurs within blood and extrahepatic tissues.

Clinical Manifestations

Jaundice persisting >2 weeks in formula-fed infants, or >3 weeks in breastfed infants.
High-colored, dark urine staining diapers.
Acholic (pale/white) stools indicating biliary obstruction or severe intrahepatic paucity of bile ducts.

Hepatomegaly, splenomegaly.
Bleeding diathesis, bruising, intracranial hemorrhage secondary to vitamin K malabsorption.
Pruritus (prominent in Alagille syndrome, progressive familial intrahepatic cholestasis [PFIC]).
Disfiguring xanthomas correlating with severe hypercholesterolemia.
Poor weight gain, failure to thrive (common in metabolic liver diseases).

Category	Specific Disorders
Extrahepatic Obstructive	Biliary atresia, choledochal cyst, inspissated bile syndrome, neonatal sclerosing cholangitis, gallstones, biliary stricture.
Infectious	Congenital TORCH infections (Toxoplasmosis, Rubella, CMV, HSV), Syphilis, bacterial sepsis, urinary tract infection.
Metabolic/Genetic	Alpha-1 antitrypsin deficiency, galactosemia, tyrosinemia, glycogen storage diseases, cystic fibrosis, bile acid synthesis defects, PFIC (types 1-6).
Anatomic/Syndromic	Alagille syndrome (paucity of interlobular bile ducts), congenital hepatic fibrosis (Caroli disease).
Endocrine	Hypothyroidism, panhypopituitarism.
Toxic/Alloimmune	Intestinal failure-associated liver disease (parenteral nutrition toxicity), gestational alloimmune liver disease (GALD).

Fractionated bilirubin confirms conjugated hyperbilirubinemia.
Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) assess hepatocellular injury and biliary stress.
Prothrombin time (PT), international normalized ratio (INR), albumin, glucose, ammonia evaluate synthetic liver function.

GGT provides highly specific diagnostic differentiation for intrahepatic cholestasis.

GGT Level	Associated Cholestatic Disorders
High GGT	Biliary atresia, Alagille syndrome, choledochal cyst, PFIC type 3, alpha-1 antitrypsin deficiency.
Low/Normal GGT	PFIC types 1, 2, 4, 6, inborn errors of bile acid synthesis, arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome, Aagenaes syndrome.

Alpha-1 antitrypsin: Serum level and Pi phenotyping required early; histology mimics biliary atresia.
Thyroid function: Thyroid-stimulating hormone (TSH), free T4 rule out central or primary hypothyroidism.
Metabolic assays: Urine succinylacetone (tyrosinemia), galactose-1-phosphate uridyltransferase (galactosemia).
Matrix metalloproteinase-7 (MMP-7): Highly sensitive and specific serum marker differentiating biliary atresia from other cholestatic causes.

Abdominal ultrasonography: Initial modality. Assesses hepatic size, gallbladder presence, biliary stones, sludge. Triangular cord sign (echogenic density >3 mm cranial to portal vein bifurcation) suggests biliary atresia.
Hepatobiliary scintigraphy (HIDA): Radiotracer excretion into bowel rules out biliary atresia. Non-excretion remains non-specific (seen in severe intrahepatic cholestasis).
Magnetic resonance cholangiopancreatography (MRCP): Evaluates structural anomalies, delineates choledochal cysts.

Percutaneous liver biopsy: Differentiates biliary atresia (portal tract expansion, bile ductular proliferation, bile plugs, fibrosis) from neonatal hepatitis (lobular architecture alteration, giant cell transformation, focal necrosis).
Intra-operative cholangiogram: Gold standard procedure definitively evaluating extrahepatic and intrahepatic biliary tree patency.

Etiology	Specific Intervention
Biliary Atresia	Kasai portoenterostomy (hepato-portoenterostomy). Optimal outcomes achieved if performed <45-60 days of life.
Choledochal Cyst	Surgical excision of abnormal biliary segment with Roux-en-Y hepaticojejunostomy.
Galactosemia	Strict elimination of galactose (galactose-free formula).
Tyrosinemia Type 1	Nitisinone administration; dietary restriction of phenylalanine and tyrosine.
Gestational Alloimmune Liver Disease (GALD)	Exchange transfusion combined with intravenous immunoglobulin (IVIG).
Congenital Hypothyroidism	Prompt thyroid hormone replacement.

Provide high-calorie diet targeting 125-150% of recommended daily allowance based on ideal body weight.
Administer formulas enriched with medium-chain triglycerides (MCT); absorbed directly into portal circulation independently of bile salts.
Supplement aqueous fat-soluble vitamins (A, D, E, K). Adjust dosages based on serial serum levels.
Maintain adequate protein intake (2-3 g/kg/day in infants, 1-2 g/kg/day in children). Restrict protein exclusively in intractable encephalopathy.

Ursodeoxycholic acid (UDCA): First-line choleretic agent (10-20 mg/kg/day). Displaces toxic hydrophobic bile acids, stimulates bile flow, provides hepatoprotection.
Rifampin: Induces hepatic microsomal enzymes; relieves severe pruritus.
Bile-acid-binding resins: Cholestyramine or colesevelam limit enterohepatic bile acid recirculation.
Naltrexone/Sertraline: Opiate antagonists and serotonin reuptake inhibitors utilized for refractory pruritus.
Apical sodium-dependent bile acid transporter inhibitors: Maralixibat, odevixibat reduce serum bile acids and alleviate debilitating pruritus in Alagille syndrome and PFIC.

Liver transplantation: Definitive therapy indicated for end-stage liver disease, failed Kasai portoenterostomy, uncorrectable metabolic defects, refractory portal hypertension, or severe intractable pruritus/xanthomas compromising quality of life.