Any disturbance in the formation or excretion of bile is called Cholestasis. The etiologies may include-

• Defects in intrahepatic production of bile, 
• Defects in the transmembrane transport of bile, 
• Mechanical obstruction to bile flow. 

Clinical features of cholestasis demonstrate the phenomenon of retention of bile components (bilirubin, bile acids, cholesterol) in the body. 

In the neonates, hyperbilirubinemia can be categorized as- 

• Unconjugated (and often benign) hyperbilirubinemia,  
• Conjugated hyperbilirubinemia due to cholestasis. 

Thus the first laboratory evaluation in a patient with jaundice, dark urine, and/or acholic stool remains to be the evaluation of fractionated bilirubin. 

Etiologies of Neonatal Cholestasis include biliary atresia, idiopathic neonatal hepatitis, gestational alloimmune liver disease, metabolic and genetic diseases, total parenteral nutrition cholestasis, as well as congenital infection. 

Source: Ananth R. Neonatal Cholestasis: A Primer of Selected Etiologies. Pediatr Ann. 2018 Nov 1;47(11):e433-e439. doi: 10.3928/19382359-20181018-01. PMID: 30423185.