Rationale and Objectives
The purpose of the present study was to obtain a cutoff value of liver fat content for the diagnosis of hepatic steatosis by comparing magnetic resonance (MR) spectroscopy results in children and adolescents with normal and excess weight.
Materials and Methods
The study included 420 children and adolescents (91 normal-weight, 99 overweight, and 230 obese) 8–18 years of age. Proton magnetic resonance spectroscopy was performed with a 3T MR system using point resolved spectroscopy sequence with series echo times.
Results
The mean absolute mass concentration of liver fat was obtained: 0.5 ± 0.04% in normal-weight boys; 0.5 ± 0.03% in normal-weight girls; 0.9 ± 0.16% in boys with overweight; 1.1 ± 0.24% in girls with overweight; 1.7 ± 0.24% in boys with obesity; and 1.4 ± 0.21% in girls with obesity.
The cutoff value of absolute mass concentration of liver fat for hepatic steatosis was found to be 1.5%. Based on this cutoff value, hepatic steatosis was diagnosed in 16% of boys with overweight, 11% of girls with overweight, 32% of boys with obesity, and 27% of girls with obesity.
Conclusions
Proton magnetic resonance spectroscopy was successfully applied to obtain the cutoff value of absolute mass concentration of liver fat for the diagnosis of hepatic steatosis in children and adolescents. Children and adolescents with obesity have higher risk of hepatic steatosis than their peers with overweight.
Introduction
Obesity has become a growing health challenge all over the world, beginning at early age in children and progressing into adulthood . One of the major complications caused and worsened by obesity is nonalcoholic fatty liver disease (NAFLD). NAFLD ranges from simple steatosis through steatohepatitis and fibrosis to end-stage liver disease (cirrhosis) and is defined as triglyceride accumulation in hepatocytes exceeding 5% of the liver weight . Liver biopsy is the gold standard of diagnosis and severity assessment of NAFLD . However, it is an invasive procedure associated with serious risks .
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Materials and Methods
Study Population
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Table 1
Study Population
Normal-weight Girls ( n = 51) Normal-weight Boys ( n = 40) Age, y BMI SDS Age, y BMI SDS Mean 13.6 0.02 12.6 0.12 Standard deviation 2.8 0.87 2.3 0.74 Minimum 8.1 −1.72 9.0 −1.70 Maximum 17.8 1.27 17.3 1.18
Girls With Overweight ( n = 62) Boys With Overweight ( n = 37) Age, y BMI SDS Age, y BMI SDS Mean 13.2 1.94 13.0 1.96 Standard deviation 2.6 0.28 2.4 0.30 Minimum 7.3 1.32 9.7 1.31 Maximum 17.8 2.32 17.9 2.32
Girls With Obesity ( n = 122) Boys With Obesity ( n = 108) Age, y BMI SDS Age, y BMI SDS Mean 13.6 2.82 13.0 3.00 Standard deviation 2.2 0.36 1.9 0.40 Minimum 8.8 2.34 8.6 2.33 Maximum 17.9 4.18 17.3 4.11
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Magnetic Resonance Examination
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Measurement of Liver Fat Content
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LFSF=(fat peak area at TE=0ms/[fat peak area at TE=0ms+water peak area at TE=0ms])×100. LFSF
=
(
fat peak area at TE
=
0
ms
/
[
fat peak area at TE
=
0
ms
+
water peak area at TE
=
0
ms
]
)
×
100
.
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LFC=0.856×([LFSF/100][1.138−0.339×{LFSF/100}]) LFC
=
0.856
×
(
[
LFSF
/
100
]
[
1.138
−
0.339
×
{
LFSF
/
100
}
]
)
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Statistical Analysis
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Results
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Table 2
Prevalence of Hepatic Steatosis (Liver Fat Signal Fraction [LFSF] Over 2%; Corresponding Absolute Mass Concentration of Liver Fat [LFC] Over 1.5%) in the Overweight and Obese Study Groups
Girls Boys Overweight 11% 16% Obese 27% 32%
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Table 3
Mean and Standard Errors of the Mean Values (SD) of Liver Fat Signal Fraction (LFSF) and the Absolute Mass Concentration of Liver Fat (LFC) in the Study Groups
LFSF, % LFC, % Mean (SD) Mean (SD) Normal-weight girls ( n = 51) 0.6 (0.04) 0.5 (0.03) Girls with overweight ( n = 62) 1.4 (0.30) 1.1 (0.24) Girls with obesity ( n = 122) 1.9 (0.26) 1.4 (0.21) Normal-weight boys ( n = 40) 0.6 (0.05) 0.5 (0.04) Boys with overweight ( n = 37) 1.2 (0.23) 0.9 (0.16) Boys with obesity ( n = 108) 2.2 (0.31) 1.7 (0.24)
Table 4
Correlation Between Liver Fat Signal Fraction (LFSF) and Body Mass Index Standard Deviation Score (BMI SDS) in the Study Groups
Girls Boys Normal-weight r = 0.014, P = .9 r = 0.15, P = .36 Overweight r = 0.22, P = .11 r = 0.17, P = .33 Obese r = 0.38, P = .0001 r = 0.05, P = .63
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Discussion
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Acknowledgments
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