The spectrum of fatty liver in obese children and the relationship of serum aminotransferases to severity of steatosis

Objectives: Non-alcoholic fatty liver disease is an emerging diagnosis in the pediatric population. Previously, ultrasonography and serum aminotransferases have been used to estimate prevalence of the disorder. A lack of concordance has been noted between these two diagnostic tests. To better understand the spectrum of fatty liver in obese children and the relationship of serum aminotransferases to the severity of steatosis, hepatic MRI was used to quantitate fat content. Methods: Twenty-two children, ages 6 to 18 years, with obesity (BMI > 95th percentile for age) and hepatomegaly (liver edge more than 2 cm below the right costal margin) underwent hepatic MRI for fat quantitation. Hepatic MRI was performed using a modification of the Dixon method that used a fast gradient echo sequence rather than traditional spin echo. Scan times were sufficiently brief to allow completion within a single breath hold. Serum aminotransferases were obtained within one month of MRI. Results: Twenty-one of 22 subjects had an elevated hepatic fat fraction. Seven of 7 subjects with a fat fraction of ≤ 18% had a normal serum ALT. Twelve of 13 subjects with fat fraction of > 18% had an elevated serum ALT. Hepatic fat fraction correlated with serum ALT but did not correlate with age, BMI, or serum AST. Conclusion: The spectrum of fatty liver is larger than detected by screening for abnormal serum aminotransferases alone. Abnormalities in serum ALT occur exclusively in more severe cases of fatty liver.