Measuring hepatic steatosis with ultrasound and MRS in children with overweight or obesity

Obesity is associated with a variety of co-morbidities. Children with obesity
are more likely to have risk factors associated with cardiovascular disease
(eg, hypertension, high cholesterol, and type 2 diabetes mellitus), but also
non-alcoholic fatty liver disease (NAFLD). A recent meta-analysis has shown
that the prevalence of NAFLD in obese pediatric populations is approximately
35%, compared to approximately 8% in general pediatric populations, making it a
very important health threat in these populations. The golden standard for the
diagnosis of NAFLD is liver biopsy. However, since liver biopsy is associated
with a certain risk of morbidity and mortality, this method is inappropriate
for screening large populations at-risk for developing NAFLD. Magnetic
resonance spectroscopy has demonstrated excellent correlation with liver biopsy
and the most accurate non-invasive method to measure liver fat content in
children. However, MRS is an expensive method that is not available in all
centers. A novel ultrasonographic measurement to quantitatively assess liver
steatosis is the hepatorenal index (HRI), which is calculated as the ratio of
hepatic and renal ultrasonographic brightness. Previous studies in adults have
shown a high sensitivity and specificity of the HRI, as compared to liver
biopsy as well as H-MRS. However, the measurement of the HRI has never been
validated in children. The validation of this simple, non-invasive method to
quantitatively assess fat accumulation in the liver, could improve the
screening for, and follow-up of, NAFLD in at-risk populations.

The aim of this study is to validate the ultrasonographic hepatorenal index in
children with overweight, obesity and morbid obesity, by using MRS.

Cross-sectional study.

MRS is a safe measurement, as long as none of the before mentioned exclusion
criteria are met. Measurements performed during the study could potentially
lead to unexpected medical findings. If the subject does not want to be
informed about incidental findings, he/she cannot participate in the study.
Lying in the MR scanner can cause some discomfort, since children have to lie
still for about 45 minutes.
In adults, the HRI has shown to be an easy, reproducible method to
quantitatively measure liver fat accumulation, with a high sensitivity and
specificity (compared to liver biopsy and MRS). However, the (validity) of the
HRI has never been studied in children. Therefore, it is unknown if this method
is also reliable in pediatric populations. Also cut-off points for children are
unknown.