Elastography as a non-invasive method of screening non-alcoholic fatty liver disease in the adult phenotype of paediatric obstructive sleep apnoea

PURPOSE: The high prevalence of non-alcoholic fatty liver disease (NAFLD) in obese children with obstructive sleep apnoea (OSA) calls for early non-invasive screening. The aim of this study was to use ultrasonographic liver echogenicity and elasticity to evaluate the early stages of liver injury in obese children with OSA. METHODS: Fifty-five obese children with OSA aged 12 to 15 years were included. The control group (n = 56) consisted of healthy, non-obese children. All children underwent ultrasound examination to assess liver echogenicity using the hepatorenal index (HRI) and real-time elastography to determine the liver fibrosis index (LFI). Polysomnographic parameters, sonographic values, and clinical-biochemical assessment were statistically analysed according to OSA and its severity. Subgroup 1 was obese children with OSA and AHI < 5 and subgroup 2 was obese children with OSA and AHI ≥ 5. RESULTS: Higher average values of HRI and LFI were recorded in the group of obese paediatric patients with OSA (mean age ± SD, 14.1 ± 2.2 year; 53% male; BMI z-score, 2.6 ± 0.35) compared to the control group (1.37 ± 0.19 vs. 1.12 ± 0.07, p < 0.001 and 1.82 ± 0.31 vs. 1.02 ± 0.27, p < 0.001). A significantly higher LFI was recorded in subgroup 2 compared to subgroup 1 (2.0 ± 0.3 vs. 1.6 ± 0.2, p < 0.001) while laboratory parameters and HRI (1.4 ± 0.2 vs. 1.4 ± 0.2, p = 0.630) did not change significantly. A strong positive correlation was found between the severity of OSA and the LFI (r = 0.454; p < 0.01). CONCLUSIONS: These findings suggest that ultrasound elastography is a useful non-invasive screening test for OSA-related steatohepatitis in obese adolescents, but other clinical studies are needed to confirm this result.