Determine the Prevalence of Exocrine Pancreatic Insufficiency (EPI) in Pediatric and Adult Participants With Alagille Syndrome After Liver Transplantation

Inclusion Criteria: * Male and female participants ages 7-50 years inclusive. * Confirmed diagnosis of ALGS * Status post OLT due to ALGS complications. * Participants currently managed with pancreatic enzyme products (PEPs) are allowed pending discontinuation of PEPs for 5 days prior to beginning the 72-hour stool collections. Participants must discontinue PEPs for the entire study period until completion. * Agree to adhere to a high fat diet at least 2 days prior to and during the 72-hour stool collections and monitor dietary consumption through the use of a diet diary. * Have a consistent caregiver for the duration of the study if applicable for enrollment of a child. * Capable of giving written informed consent and assent (if age appropriate). Exclusion Criteria: * Surgical disruption of the enterohepatic circulation (e.g., biliary diversion). * Subjects with alternative etiologies of EPI (e.g., chronic panreatitis, pancreatic resection). * Diets high in medium-chain triglyceride (MCT) oil. * Use of bile acids, bile acid uptake inhibitors, lipid-binding resins, synthetic fat substitutes (e.g. Olestra), and diaper rash ointments (note that H2 antagonists and proton pump inhibitors \[PPIs\] are permitted if on a stable and consistent regimen throughout the duration of the study). * History or presence of other concomitant liver diseases such as liver transplant rejection with cholestasis, hepatitis B or C virus infection, HIV, primary sclerosing cholangitis (PSC), alcoho…