A six-month boy is having persistent jaundice since birth. Initially, he had whitish stool but now he is having yellowish stool. His USG shows hepatosplenomegaly but no intrahepatic bile duct (IHBD) dilatation. Cbc--Hb-10.9, TSB dated - 20/10/2015--8.25, D-5.38, I-2.86, SGOT--222, SGPT--268, S Alk Phos--877..

26/11/2015 S bilirubin - 7.9,,D-1.I--6.9. 18/12/2015--TSB--12.6 DIR-7.1, Ret Count--2.2, TSH-1.94. What are the causes of persistent direct bilirubin with normal IHBD, how to approach?