In neonatal cholestasis, if the serum gamma glutamyl transpeptidase (GGT) is more than 600 IU/L, the most likely diagnosis is:

3 Enzymes reflect cholestasis: Alkaline phosphatase, 5'nucleotidase & Gamma glutamyl transpeptidase. About GGT in Cholestasis: (Normal value of GGT is 5-40 IU/L) "GGT levels are commonly elevated to values more than 10 times normal in biliary atresia while in hepatic causes it is raised to about three times normal" Value of 600 IU/L in the patient- elevation of more than ten times the normal value: 'biliary atresia'.