60-year-old male with history of HCV cirrhosis s/p deceased donor liver transplant with duct-to-duct biliary anastomosis six months ago presents with jaundice, dark urine, pruritus, and pale stools. Exam is notable for icterus. Labs revealed a total bilirubin of 10 mg/dL, direct bilirubin 5 mg/dL, ALP 538 u/L, AST 36 u/L, and ALT 41 u/L. INR is 1.0. Labs from three weeks prior were notable for a normal bilirubin and mildly elevated ALP to 181 u/L which has been rising. Doppler ultrasound reveals coarsened hepatic echotexture, patent vessels, and intrahepatic biliary dilatation to 1cm.
What is the next best step?