The goal of this clinical trial is to determine the prevalence of exocrine pancreatic insufficiency (EPI) in a population of pediatric and adult participants with Alagille Syndrome (ALGS) post liver transplant. During the study, participants will:

• Consume a high fat diet
• Keep a diary of their abdominal signs and symptoms, and stool frequency and consistency
• Collect stool for laboratory testing

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), alcoholic liver disease, autoimmune hepatitis, metabolic-associated fatty liver disease (MASLD)/non-alcoholic steatohepatitis (NASH) or significant chronic allograft rejection.
• Currently pregnant or breastfeeding.
• Cancers except for in situ carcinoma or cancers treated at least 5 years prior to screening with no evidence of recurrence.
• Participation in a clinical trial and received an investigational product within the last 30 days.
• Use of anti-diarrheal, anti-spasmodic, and/or cathartic laxatives. Change in osmotic laxatives within the past 3 months.

Male and female participants ages 7-50 years inclusive with a confirmed diagnosis of ALGS status post OLT due to ALGS complications.