The goal of this study is to determine if ultrasound tools can be used to detect liver stiffness. Acoustic radiation force impulse (ARFI) elastography and backscatter will be used to see if they can detect liver stiffness in different populations of patients with liver disease.

The study is measuring liver stiffness in pediatric patients aged 2-5 years. Patients either have had a Fontan cardiac surgery or have liver disease.

Ultrasound scanning takes images of the liver and has much lower risks for patients. ARFI elastography and other tools can be used to measure liver stiffness.

If patients have liver congestion, reversing it could prevent liver fibrosis, which cannot be treated. Liver fibrosis has serious health risks and is associated with a higher chance of developing liver cancer later in life.

Subjects from two patient populations will be enrolled in order to test ultrasound technologies. A total of 30 subjects between 2-5 years of age will be enrolled.

1. 15 children with increased liver stiffness due to the Fontan operation
2. 15 children with increased liver stiffness caused by Biliary Atresia.

Inclusion Criteria:

• Patients aged 2-5 years
• Children who are scheduled to have a Stage 3 Fontan cardiac operation (arm 1) AND Children who have chronic liver disease caused by biliary atresia (arm 2)
• Patient must be receiving care at the University of Michigan CS Mott Children's Hospital
• Parent/guardian must be willing to sign the study consent form

Exclusion Criteria:

• For arm 1 subjects: pre-existing evidence of chronic liver disease (as defined by chronic elevation (over 4 weeks) of alanine aminotransferase (ALT), aspartate aminotransferase (AST), or conjugated bilirubin to greater than two times the upper limit of normal
• For arm 1 subjects: evidence of overt liver nodularity by conventional US imaging or evidence of portal vein or hepatic vein thrombosis (clots) by US Doppler exam

Patients will either be scheduled for a Stage 3 Fontan cardiac operation or have chronic liver disease caused by biliary atresia.