Patients younger than 18 years of age with the following International Classification of Diseases, 10th Revision, codes at admission were included in the case series: hepatitis (K75.9), transaminitis (R74.01), elevated liver enzymes (R74.8), liver failure (K72.9), and acute liver failure (K72.00). Identified causes of hepatitis included cholangitis associated with complications of biliary atresia (1 patient), autoimmune hepatitis (2 patients), liver shock after a code event (1 patient), acetaminophen overdose (1 patient), and complicated urinary tract infection (1 patient). A total of 9 patients with acute hepatitis and human adenovirus viremia were included in this case series.