Sonographic pediatric liver size standards based on generalized additive modeling in a diverse population

BACKGROUND: In pediatric radiology, assessment of liver size is a fundamental component of abdominal imaging, reflecting both normal hepatic growth and potential pathologic processes. Limitations in prior literature, along with evolving demographic characteristics of the pediatric population, highlight the need for updated, methodologically rigorous reference ranges for normal liver size on ultrasound. OBJECTIVE: This study aims to establish contemporary ultrasound-based reference ranges for pediatric liver size, incorporating both age and height as key variables. MATERIALS AND METHODS: In this retrospective study, radiology reports from January 2014 to December 2024 for patients under 18 years of age were reviewed. Patients with an impression of "normal abdominal ultrasound" were included, excluding those with liver diseases or abnormal Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) results. Standard liver length measurement for our institution is the craniocaudal dimension of the right lobe along the midclavicular line. Generalized Additive Models for Location, Scale, and Shape (GAMLSS) with the Box-Cox Power Exponential (BCPE) distribution was used to create reference ranges based on patients' age and height. RESULTS: A total of 4,611 abdominal ultrasound examinations met the inclusion criteria. The study included 2,055 males (44.6%) and 2,556 females (55.4%). At birth, the liver size ranged from 4.9 to 5.5 cm (cm), increasing progressively with age to a maximum of 17.2 cm in adolescents aged 17-18 years. A subset of 3,235 examinations (70%) with recorded height was used for GAMLSS modeling, showing a more linear increase in liver size with height. Reference ranges were reported up to 180 cm in height, with a maximum liver size of 17.5 cm. CONCLUSION: This study provides updated reference ranges and nomograms for pediatric liver size based on age and height, which support a normal liver size slightly higher than previously reported.