T1-weighted dual-echo MRI for fat quantification in pediatric nonalcoholic fatty liver disease

AIM:To determine in obese children with nonalcoholic fatty liver disease (NAFLD) the accuracy of magnetic resonance imaging (MRI) in assessing liver fat concentration.METHODS:A case-control study was performed.Cases were 25 obese children with biopsy-proven NAFLD.Controls were 25 obese children matched for age and gender,without NAFLD at ultrasonography and with normal levels of aminotransferases and insulin.Hepatic fat fraction (HFF) by MRI was obtained using a modification of the Dixon method.RESULTS:HFF ranged from 2% to 44% [mean,19.0% (95% CI,15.1-27.4)] in children with NAFLD,while in the controls this value ranged from 0.08% to 4.69% [2.0% (1.3-2.5),P < 0.0001].HFF was highly correlated with histological steatosis (r=0.883,P < 0.0001) in the NAFLD children.According to the histological grade of steatosis,the mean HFF was 8.7% (95% CI,6.0-11.6) for mild,21.6% (15.3-27.0) for moderate,and 39.7% (34.4-45.0) for severe fatty liver infiltration.With a cutoff of 4.85%,HFF had a sensitivity of 95.8% for the diagnosis of histological steatosis ≥ 5%.All control children had HFF lower than 4.85%;thus,the specificity was 100%.After 12 mo,children with weight loss displayed a significant decrease in HFF.CONCLUSION:MRI is an accurate methodology for liver fat quantification in pediatric NAFLD.

Pancreatic fat and β-cell function in overweight/obese children with nonalcoholic fatty liver disease

AIM: To analyze the associations of pancreatic fat with other fat depots and β-cell function in pediatric nonalcoholic fatty liver disease(NAFLD).METHODS: We examined 158 overweight/obese children and adolescents, 80 with NAFLD [hepatic fat fraction(HFF) ≥ 5%] and 78 without fatty liver. Visceral adipose tissue(VAT), pancreatic fat fraction(PFF) and HFF were determined by magnetic resonance imaging. Estimates of insulin sensitivity were calculated using the homeostasis model assessment of insulin resistance(HOMA-IR), defined by fasting insulin and fasting glucose and whole-body insulin sensitivity index(WBISI), based on mean values of insulin and glucose obtained from oral glucose tolerance test and the corresponding fasting values. Patients were considered to have prediabetes if they had either:(1) impaired fasting glucose, defined as a fasting glucose level ≥ 100 mg/d L to < 126 mg/d L;(2) impaired glucose tolerance, defined as a 2 h glucose concentration between ≥ 140 mg/d L and < 200 mg/d L; or(3) hemoglobin A1 c value of ≥ 5.7% to < 6.5%.RESULTS: PFF was significantly higher in NAFLD patients compared with subjects without liver involvement. PFF was significantly associated with HFF and VAT, as well as fasting insulin, C peptide, HOMA-IR, and WBISI. The association between PFF and HFF was no longer significant after adjusting for age, gender, Tanner stage, body mass index(BMI)-SD score, and VAT. In multiple regression analysis withWBISI or HOMA-IR as the dependent variables, against the covariates age, gender, Tanner stage, BMI-SD score, VAT, PFF, and HFF, the only variable significantly associated with WBISI(standardized coefficient B,-0.398; P = 0.001) as well as HOMA-IR(0.353; P = 0.003) was HFF. Children with prediabetes had higher PFF and HFF than those without. PFF and HFF were significantly associated with prediabetes after adjustment for clinical variables. When all fat depots where included in the same model, only HFF remained significantly associated with prediabetes(OR = 3.38; 95%CI: 1.10-10.4; P = 0.034).CONCLUSION: In overweight/obese children with NAFLD, pancreatic fat is increased compared with those without liver involvement. However, only liver fat is independently related to prediabetes.

Comparison of magnetic resonance spectroscopy, proton density fat fraction and histological analysis in the quantification of liver steatosis in children and adolescents

AIM To establish a threshold value for liver fat content between healthy children and those with nonalcoholic fatty liver disease(NAFLD) by using magnetic resonance imaging(MRI), with liver biopsy serving as a reference standard. METHODS The study was approved by the local ethics committee, and written informed consent was obtained from all participants and their legal guardians before the study began. Twenty-seven children with NAFLD underwent liver biopsy to assess the presence of nonalcoholic steatohepatitis. The assessment of liver fat fraction was performed using MRI, with a high field magnet and 2D gradient-echo and multiple-echo T1-weighted sequence with low flip angle and single-voxel pointresolved 1H MR-Spectroscopy(1H-MRS), corrected for T1 and T2* decays. Receiver operating characteristic curve analysis was used to determine the best cutoff value. Lin coefficient test was used to evaluate thecorrelation between histology, MRS and MRI-PDFF. A Mann-Whitney U-test and multivariate analysis were performed to analyze the continuous variables. RESULTS According to MRS, the threshold value between healthy children and those with NAFLD is 6%; using MRI-PDFF, a cut-off value of 3.5% is suggested. The Lin analysis revealed a good fit between the histology and MRS as well as MRI-PDFF.CONCLUSION MRS is an accurate and precise method for detecting NAFLD in children.

Locoregional therapy response in patients with hepatocellular cancer waiting for liver transplantation:Only selection or biological effect?

Locoregional treatments(LRT) represent a broad strategy used for reducing the risk of drop-off and contextually improving the survivals in patients with hepatocellular cancer receiving a liver transplantation(LT). However, it is not sufficiently clear if LRT are only a surrogate of tumor aggressiveness or if they consent a real benefit in terms of tumor stabilization. A recent study by Pommergaard et al reported the results from the European Liver Transplant Registry. Patients receiving LRT before LT had better 5-year survival rates respect to no-LRT cases(69.7% vs 65.8%; P < 0.001). When the number of LRT was tested, one-to-two treatments were connected with improved survivals respect to no treatment [hazard ratio(HR) = 0.85 and 0.71, respectively]. The efficacy of LRT was also reported in the presence of larger tumors(HR = 0.78) and micro-macrovascular invasion(HR = 0.71). The results observed in the present study are partially in discordance with other analyses showing a detrimental effect of LRT. The main problem in the interpretation of these results is connected with the possible initial selection biases present in the studies. The most recent guidelines suggest to perform LRT before the transplant, but the level of evidence is typically low due to the absence of prospectively designed studies.