Hepatic MRI for fat quantitation: its relationship to fat morphology, diagnosis, and ultrasound

Pediatric hepatobiliary magnetic resonance imaging

Magnetic resonance (MR) imaging is an effective and noninvasive modality for evaluating hepatobiliary pathologic conditions. This article provides an up-to-date review of anatomy, indications, and imaging goals and protocols, including patient preparation, pulse sequences, and contrast agents used in pediatric MR hepatobiliary imaging. This article also highlights some of the common MR features of pediatric liver pathologic conditions, including tumors, congenital biliary ductal plate malformations, trauma, fibrosis, and infection.

Non-alcoholic fatty liver disease: non-invasive investigation and risk stratification

Non-alcoholic fatty liver disease (NAFLD) encompasses a histological spectrum of liver disease, from simple steatosis through to cirrhosis. As the worldwide rates of obesity have increased, NAFLD has become the commonest cause of liver disease in many developed countries, affecting up to a third of the population. The majority of patients have simple steatosis that carries a relatively benign prognosis. However, a significant minority have non-alcoholic steatohepatitis, and have increased liver related and cardiovascular mortality. Identifying those at risk of progressive disease is crucial. Liver biopsy remains the gold standard investigation for assessing stage of disease but its invasive nature makes it impractical for widespread use as a prognostic tool. Non-invasive tools for diagnosis and disease staging are required, reserving liver biopsy for those patients where it offers clinically relevant additional information. This review discusses the non-invasive modalities available for assessing steatosis, steatohepatitis and fibrosis. We propose a pragmatic approach for the assessment of patients with NAFLD to identify those at high risk of progressive disease who require referral to specialist services.

Magnetic resonance imaging of the pediatric liver: imaging of steatosis, iron deposition, and fibrosis

Traditionally, many diffuse diseases of the liver could only be diagnosed by liver biopsy. Although still considered the gold standard, liver biopsy is limited by its small sample size, invasive nature, and subjectivity of interpretation. There have been significant advances in functional magnetic resonance (MR) imaging of the liver. These advances now provide radiologists with the tools to evaluate the liver at the molecular level, allowing quantification of hepatic fat and iron, and enabling the identification of liver fibrosis at its earliest stages. These methods provide objective measures of diffuse liver processes and aid hepatologists in the diagnosis and management of liver disease.

Interobserver concordance in controlled attenuation parameter measurement, a novel tool for the assessment of hepatic steatosis on the basis of transient elastography

BACKGROUND

The combination of transient elastometry with a controlled attenuation parameter (CAP) is available to evaluate hepatic steatosis (HS) along with liver stiffness.

AIMS

To assess the concordance of CAP measurements between two independent observers in patients infected by HIV and/or hepatitis virus, as well as to determine the concordance of classification of the grade of HS using two cut-off values.

MATERIALS AND METHODS

In a cross-sectional prospective study, CAP-enabled transient elastometry acquisitions were performed by two independent observers in patients with HIV or hepatitis virus infection. The interobserver concordance between the CAP examinations was assessed using the intraclass correlation coefficient and the concordance in the classification of patients in the grades of HS was characterized using the κ index.

RESULTS

A total of 118 patients were included. Twenty (17%) patients were HIV monoinfected, 44 (37.3%) were hepatitis C virus monoinfected, and 52 (44%) had HIV/hepatitis C virus coinfection. The median (Q1-Q3) of the absolute difference of CAP values between the two observers was 20 (10-41) dB/m. The overall intraclass correlation coefficient was 0.84 (95% confidence interval: 0.77-0.88). The corresponding figures for liver stiffness measurements were 0.9 (0.4-2.6) kPa and 0.96 (95% confidence interval: 0.94-0.97). The κ indexes for the concordance of classification for the presence of HS, cut-off of 215 dB/m, and significant HS, cut-off of 252 dB/m, were 0.53 and 0.62, respectively.

CONCLUSION

The determination of HS by means of CAP in HIV and/or hepatitis virus infection represents an observer-independent and easily performable method. However, the use of cut-off values for the classification of patients is suboptimal.

Determinants of second-order bile duct visualization at CT cholangiography in potential living liver donors

OBJECTIVE

The purpose of this article is to investigate the determinants of second-order bile duct visualization at CT cholangiography in living potential liver donors.

MATERIALS AND METHODS

We retrospectively identified 143 potential living liver donors (83 men and 60 women; mean age, 37 years) evaluated with CT cholangiography, which included a slow infusion of iodipamide meglumine with CT acquisition 15 minutes after biliary contrast agent administration. Two readers independently scored the visualization of the second-order bile duct branches on a previously established 4-point scale (0 = not seen, 1 = faintly seen, 2 = well seen, and 3 = excellent visualization). Multivariate analysis was used to investigate the correlation between visualization scores and potential determinants of second-order bile duct opacification, specifically age, body mass index, creatinine level, total and direct bilirubin levels, alkaline phosphatase level, aspartate aminotransferase level, alanine aminotransferase level, patient maximum linear width, CT noise, and hepatosplenic attenuation difference at unenhanced CT.

RESULTS

The mean (± SD) second-order bile duct visualization scores were 2.35 ± 0.66 and 2.55 ± 0.60 for readers 1 and 2, respectively. In the multivariate analysis, the only independent predictors of reduced second-order bile duct visualization were higher alkaline phosphatase level (p = 0.01) and higher CT noise (p = 0.02).

CONCLUSION

Higher serum alkaline phosphatase level and higher CT noise in potential living liver donors indicate a higher risk of poor second-order bile duct visualization at CT cholangiography.

Ultrasound evaluation and correlates of fatty liver disease: a population study in a Mediterranean area

BACKGROUND

The aim of this study was to evaluate the distribution of fatty liver-nonalcoholic (NAFL) and alcoholic (AFL)-and its association with metabolic syndrome and its components in a population sample from a Mediterranean area.

METHODS

A sample of 2974 subjects (1679 males, 1295 females, age range 30-89 years) was randomly drawn from the population of a town in southern Italy. The survey visit included a validated semiquantitative food frequency questionnaire, anthropometric measurements, a blood sample taken in the morning after overnight fasting, as well as abdominal ultrasound examination to evaluate liver fat with a standardized scoring system. The 2001 National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) definition of the metabolic syndrome was adopted.

RESULTS

In this Mediterranean population, where alcohol intake is mostly as wine with meals, NAFL is present in 36.8% of men and 25.7% of women and AFL in 13.8% of men and 5.5% of women. NAFL and AFL are associated with metabolic syndrome and its characteristics, body mass index (BMI), and visceral and subcutaneous fat (in AFL subjects, only in women) measured by ultrasound. Stratifying by BMI and controlling for confounders (age, height, smoking habit, and alcohol consumption), in overweight and obese subjects, liver and visceral fat are associated with the metabolic syndrome both in men and women and subcutaneous fat only in women. In normal weight subjects, only liver fat in men is associated with the metabolic syndrome.

CONCLUSIONS

Fatty liver is highly prevalent in this Mediterranean population and is associated with metabolic syndrome in overweight and obese men and women as well as in men with normal BMI.

Non-invasive diagnosis of non-alcoholic fatty liver disease. A critical appraisal

Non-alcoholic fatty liver disease (NAFLD) affects one in every three subjects in the occidental world. The vast majority will not progress, but a relevant minority will develop liver cirrhosis and its complications. The classical gold standard for diagnosing and staging NAFLD and assessing fibrosis is liver biopsy (LB). However, it has important sample error issues and subjectivity in the interpretation, apart from a small but real risk of complications. The decision to perform an LB is even harder in a condition so prevalent such as NAFLD, in which the probability of finding severe liver injury is low. In an attempt to overcome LB and to subcategorize patients with NAFLD in different prognoses allowing better management decisions, several non-invasive methods have been studied in the last decade. The literature is vast and confusing. This review will summarize which methods have been tested and how they perform, which tests are adequate for clinical practice and how they can change the management of these patients.

Association between metabolic syndrome and the development of non-alcoholic fatty liver disease

The aim of this study was to examine the effects of metabolic syndrome (MS) and the number of MS components on the development of non-alcoholic fatty liver disease (NAFLD). A total of 1,343 males and 574 females aged ≥50 years without NAFLD at baseline were included. Information on lifestyle, including alcohol use and personal history, was collected by face-to-face interviews. Biochemical parameters were assayed using fasting blood samples. NAFLD was diagnosed by abdominal ultrasonography. During follow-up at an average of 4.8 years, 223 patients developed NAFLD. Following adjustment for multiple covariates, age was an independent protective predictor [hazard ratio (HR), 0.96; 95% confidence interval (CI), 0.95-0.98], while the independent risk predictors were obesity (HR, 2.81; 95% CI, 2.14-3.69), higher triglycerides (HR, 2.56; 95% CI, 1.95-3.32) and alanine aminotransferase (HR, 1.004; 95% CI, 1.000-1.008). Participants with a diagnosis of MS had a significantly increased risk of developing NAFLD (HR, 3.17; 95% CI, 2.42-4.14). A greater number of MS components was significantly associated with a higher risk of NAFLD (all adjusted P for trend <0.001). Compared with those without any components of MS, participants with only one component of MS had a 3.6-fold higher risk of developing NAFLD (adjusted HR, 3.64; 95% CI, 1.50-8.88). The diagnosis and the number of components of MS were prospectively associated with the risk of developing NAFLD. Even in those with only one component of MS, the risk increased by 2.6-fold compared with that for the individuals without any components, suggesting a beneficial effect of intervention at the very early stage of MS on the prevention of NAFLD.

Diagnostic imaging in obesity

Magnetic resonance of the body offers different techniques for mapping fat deposits (MR Imaging) and analysis of organs with small amounts of lipids (MR Spectroscopy). Possible approaches for whole-body assessment of adipose tissue are presented and discussed and spectroscopic examinations in different organs are depicted. With magnetic resonance imaging (MRI) it has been shown that obesity per se is not a marker for metabolic failure, but depends on regional variations of body composition and ectopic lipid accumulation. In addition MRI of the brain is a powerful research tool to understand the brain's role in the development and maintenance of obesity and the overconsumption of foods in obese individuals. Sonography has a low accuracy in estimating hepatic steatosis until now. New sonographic methods have been evaluated to detect hepatic steatosis by physical properties of fatty tissue as tissue stiffness, sound absorption or sound speed. Nuclear medicine and in particular Positron Emission Tomography (PET) methods are used to explore central pathophysiology, brown adipose tissue activity and alterations in homeostatic feedback and gut-brain communication.

[Non-alcoholic fatty liver disease in obese children and adolescents]

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in children and adolescents in industrialized countries. Recent studies have demonstrated a prevalence rate of NAFLD in overweight and obese children and adolescents in Germany of up to 30%. The spectrum of NAFLD ranges from pure fatty infiltration (simple steatosis) to inflammation (steatohepatitis, synonymous NASH) to fibrosis and cirrhosis. Age, gender, ethnicity, insulin resistance, and sex steroids are implicated in the pathogenesis of NAFLD in childhood and adolescence. Moreover, NAFLD in the pediatric age group is associated with marked cardiovascular comorbidities. This review focuses on current data regarding epidemiology, pathophysiology, comorbidities, and treatment of NAFLD in children and adolescents.

Diagnostic performance of a rapid magnetic resonance imaging method of measuring hepatic steatosis

OBJECTIVES

Hepatic steatosis is associated with an increased risk of developing serious liver disease and other clinical sequelae of the metabolic syndrome. However, visual estimates of steatosis from histological sections of biopsy samples are subjective and reliant on an invasive procedure with associated risks. The aim of this study was to test the ability of a rapid, routinely available, magnetic resonance imaging (MRI) method to diagnose clinically relevant grades of hepatic steatosis in a cohort of patients with diverse liver diseases.

MATERIALS AND METHODS

Fifty-nine patients with a range of liver diseases underwent liver biopsy and MRI. Hepatic steatosis was quantified firstly using an opposed-phase, in-phase gradient echo, single breath-hold MRI methodology and secondly, using liver biopsy with visual estimation by a histopathologist and by computer-assisted morphometric image analysis. The area under the receiver operating characteristic (ROC) curve was used to assess the diagnostic performance of the MRI method against the biopsy observations.

RESULTS

The MRI approach had high sensitivity and specificity at all hepatic steatosis thresholds. Areas under ROC curves were 0.962, 0.993, and 0.972 at thresholds of 5%, 33%, and 66% liver fat, respectively. MRI measurements were strongly associated with visual (r(2) = 0.83) and computer-assisted morphometric (r(2) = 0.84) estimates of hepatic steatosis from histological specimens.

CONCLUSIONS

This MRI approach, using a conventional, rapid, gradient echo method, has high sensitivity and specificity for diagnosing liver fat at all grades of steatosis in a cohort with a range of liver diseases.

Long-term follow-up of hepatic ultrasound findings in subjects with magnetic resonance imaging defined hepatic steatosis following clinical islet transplantation: a case-control study

Hepatic steatosis is one complication patients may experience following clinical islet transplantation (CIT), yet the cause and consequences of this are poorly understood. The purpose of this case-control study was to examine the relationship between hepatic steatosis, metabolic parameters and graft function in an Albertan cohort of CIT recipients. Hepatic steatosis was detected by magnetic resonance imaging (MRI) in n = 10 cases age-matched with n=10 MRI-negative controls. Progression/regression of steatosis was determined by ultrasound (US) in cases. Hepatic steatosis first appeared 2.8 ± 2.2 (mean ± SD) years post-CIT, and lasted approximately 4.6 ± 2.0 years. In five cases steatosis resolved, with recurrence in two cases during the follow-up period (8.5 ± 3.2 years). No evidence of CIT causing deleterious effects on long-term liver function or graft outcome was observed.

Longitudinal effects of MRI-measured hepatic steatosis on biomarkers of glucose homeostasis and hepatic apoptosis in obese youth

OBJECTIVE

We used fast-gradient magnetic resonance imaging (MRI) to determine the longitudinal associations between the hepatic fat content (HFF), glucose homeostasis, and a biomarker of hepatocellular apoptosis in obese youth.

RESEARCH DESIGN AND METHODS

Baseline and longitudinal liver and abdominal MRI were performed with an oral glucose tolerance test in 76 obese youth followed for an average of 1.9 years. Cytokeratin-18 (CK-18) was measured at baseline and follow-up as a biomarker of hepatic apoptosis. The relationship between baseline HFF and metabolic parameters and circulating levels of CK-18 at follow-up were assessed using a bivariate correlation.

RESULTS

At baseline, 38% had hepatic steatosis based on %HFF ≥5.5% with alterations in indices of insulin sensitivity and secretion. At follow-up, BMI increased in both groups and baseline %HFF correlated strongly with the follow-up %HFF (r = 0.81, P < 0.001). Over time, markers of insulin sensitivity and 2-h glucose improved significantly in the group without fatty liver, in contrast with the persistence of the insulin resistance and associated correlates in the fatty liver group. Baseline HFF correlated with 2-h glucose (r = 0.38, P = 0.001), whole-body insulin sensitivity (r = -0.405, P = 0.001), adiponectin (r = -0.44, P < 0.001), CK-18 levels, (r = 0.63, P < 0.001), and disposition index (r = -0.272, P = 0.021) at follow-up. In a multivariate analysis, we showed that baseline HFF is an independent predictor of 2-h glucose and whole-body insulin sensitivity.

CONCLUSIONS

In obese youth, the phenotype of MRI-measured hepatic steatosis is persistent. Baseline HFF strongly modulates longitudinally 2-h blood glucose, biomarkers of insulin resistance, and hepatocellular apoptosis.

Effect of colesevelam on liver fat quantified by magnetic resonance in nonalcoholic steatohepatitis: a randomized controlled trial

Bile acid sequestrants (BAS) lower plasma low density lipoprotein levels and improve glycemic control. Colestimide, a BAS, has been claimed by computed tomography to reduce liver fat. Therefore, we examined the efficacy of colesevelam, a potent BAS, to decrease liver fat in patients with biopsy-proven nonalcoholic steatohepatitis (NASH). Liver fat was measured by a novel magnetic resonance imaging (MRI) technique, the proton-density-fat-fraction (PDFF), as well as by conventional MR spectroscopy (MRS). Fifty patients with biopsy-proven NASH were randomly assigned to either colesevelam 3.75 g/day orally or placebo for 24 weeks. The primary outcome was change in liver fat as measured by MRI-PDFF in colocalized regions of interest within each of the nine liver segments. Compared with placebo, colesevelam increased liver fat by MRI-PDFF in all nine segments of the liver with a mean difference of 5.6% (P = 0.002). We cross-validated the MRI-PDFF-determined fat content with that assessed by colocalized MRS; the latter showed a mean difference of 4.9% (P = 0.014) in liver fat between the colesevelam and the placebo arms. MRI-PDFF correlated strongly with MRS-determined hepatic fat content (r(2) = 0.96, P < 0.0001). Liver biopsy assessment of steatosis, cellular injury, and lobular inflammation did not detect any effect of treatment.

CONCLUSION

Colesevelam increases liver fat in patients with NASH as assessed by MRI as well as MRS without significant changes seen on histology. Thus, MRI and MRS may be better than histology to detect longitudinal changes in hepatic fat in NASH. Underlying mechanisms and whether the small MR-detected increase in liver fat has clinical consequences is not known.

Is nonalcoholic fatty liver disease in children the same disease as in adults?

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children, and can present in toddlerhood. There is a differential distribution of NAFLD in children based on race and gender. The gold standard for diagnosis and classification of pediatric NAFLD is liver biopsy although ongoing studies aim to identify and define noninvasive investigations for pediatric NAFLD. Treatments that have been shown to be successful in adult NAFLD, such as insulin sensitizers and Vitamin E, have not been proven to be as definitively successful in children with NAFLD.

Correlation between liver histology and novel magnetic resonance imaging in adult patients with non-alcoholic fatty liver disease - MRI accurately quantifies hepatic steatosis in NAFLD

BACKGROUND

Conventional magnetic resonance imaging (MRI) techniques that measure hepatic steatosis are limited by T1 bias, T(2)* decay and multi-frequency signal-interference effects of protons in fat. Newer MR techniques such as the proton density-fat fraction (PDFF) that correct for these factors have not been specifically compared to liver biopsy in adult patients with non-alcoholic fatty liver disease (NAFLD).

AIM

To examine the association between MRI-determined PDFF and histology-determined steatosis grade, and their association with fibrosis.

METHODS

A total of 51 adult patients with biopsy-confirmed NAFLD underwent metabolic-biochemical profiling, MRI-determined PDFF measurement of hepatic steatosis and liver biopsy assessment according to NASH-CRN histological scoring system.

RESULTS

The average MRI-determined PDFF increased significantly with increasing histology-determined steatosis grade: 8.9% at grade-1, 16.3% at grade-2, and 25.0% at grade-3 with P ≤ 0.0001 (correlation: r(2) = 0.56, P < 0.0001). Patients with stage-4 fibrosis, when compared with patients with stage 0-3 fibrosis, had significantly lower hepatic steatosis by both MRI-determined PDFF (7.6% vs. 17.8%, P < 0.005) and histology-determined steatosis grade (1.4 vs. 2.2, P < 0.05). NAFLD patients with grade 1 steatosis were more likely to have characteristics of advanced liver disease including higher average AST:ALT (0.87 vs. 0.60, P < 0.02), GGT (140 vs. 67, P < 0.01), and INR (1.06 vs. 0.99, P < 0.01), higher stage of fibrosis and hepatocellular ballooning.

CONCLUSIONS

MRI-determined proton density-fat fraction correlates with histology-determined steatosis grade in adults with NAFLD. Steatosis is non-linearly related to fibrosis progression. In patients with NAFLD, a low amount of hepatic steatosis on imaging does not necessarily indicate mild disease.

Nonalcoholic fatty liver disease

As the hepatic manifestation of the metabolic syndrome, nonalcoholic fatty liver disease (NAFLD) has become the most common cause of asymptomatic liver enzyme elevations in Western nations. Although it is easy to diagnose NAFLD, a liver biopsy is currently required to diagnose nonalcoholic steatohepatitis (NASH). Patients with NASH are those at greatest risk of progression to cirrhosis and, thus, treatment efforts are targeted to these individuals. Although currently there are no FDA-approved treatments for NASH, a multidisciplinary approach that addresses comorbid conditions and promotes modest weight loss comprises the backbone of therapy.

PPARG gene Pro12Ala variant contributes to the development of non-alcoholic fatty liver in middle-aged and older Chinese population

Oxidative stress has been suggested to contribute to the development of non-alcoholic fatty liver disease (NAFLD). Peroxisome proliferator-activated receptor gamma (PPAR-γ) heterozygous mice and Pro12Ala (C/G) polymorphism in PPARG exhibited increased resistance to oxidative stress. Smoking increases the production of reactive oxygen species, which could accelerates oxidative stress under overnutrition. To explore whether the C/G polymorphism, alone or in combination with smoking, may promote the development of non-alcoholic fatty liver, a case-control study was performed in 903 Chinese subjects. Among the study population, 436 patients with B-mode ultrasound-proven NAFLD (318 with steatosis hepatis I°, 90 with steatosis hepatis II° and 28 with steatosis hepatis III°) and 467 controls were genotyped by using TaqMan allelic discrimination assays. After adjusting for confounders, the C/C genotype significantly associated with NAFLD (OR=1.87, 95%CI 1.13-2.85, p=0.009); smoking was also an independent risk factor for NAFLD (OR=1.69, 95%CI 1.18-2.43, p=0.025). In addition, we found possible synergistic effects, the higher risk group (smokers with the C/C genotype) showed 3.75 times higher risk of NAFLD than the low-risk group (non-smokers with C/G genotype) in a multiple logistic analysis after adjusting for the confounders (p<0.001), but no departure from additivity was found. Our results indicated that the C/C genotype and smoking were significant independent risk factors for NAFLD. The possible synergistic effects of genotype and smoking may promote the development of NAFLD by aggravating oxidative stress, which supports the hypothesis that oxidative stress contributes to the development of NAFLD.

Diagnosis and evaluation of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of elevated liver function tests results, after the commonly investigated causes have been excluded, and frequently coexists with type 2 diabetes mellitus (T2DM) because the conditions have common risk factors. As both T2DM and NAFLD are related to adverse outcomes of the other, diagnosis and valuation of fatty liver is an important part of the management of diabetes. Although noninvasive methods, such as biomarkers, panel markers, and imaging, may support a diagnostic evaluation of NAFLD patients, accurate histopathological findings cannot be achieved without a liver biopsy. As it is important to know whether steatohepatitis and liver fibrosis are present for the management of NAFLD, liver biopsy remains the gold standard for NAFLD diagnosis and evaluation. Therefore, new investigations of the pathogenesis of NAFLD are necessary to develop useful biomarkers that could provide a reliable noninvasive alternative to liver biopsy.

Prevalence of non-alcoholic fatty liver disease and its relation to hypoadiponectinaemia in the middle-aged and elderly Chinese population

INTRODUCTION

Hypoadiponectinaemia is an important risk factor for non-alcoholic fatty liver disease (NAFLD). However, little is known about its role in the Chinese population. This study sought to assess the prevalence of NAFLD and its association with hypoadiponectinaemia in middle-aged and elderly Chinese.

MATERIAL AND METHODS

We conducted a population-based cross-sectional study in an urban Shanghai sample of 2201 participants age 50 years to 83 years (973 men, 1228 women). Hepatic ultrasonographic examination was performed for all participants. Serum adiponectin concentrations were measured by ELISA methods.

RESULTS

The prevalence of NAFLD was 19.8% (16.0% in men, 22.8% in women). Serum adiponectin levels were significantly higher in female than in male subjects (p < 0.001). Serum adiponectin levels were significantly lower in NAFLD subjects than those in control subjects (p < 0.001). The prevalence of NAFLD progressively increased with declining adiponectin levels (p(for trend) < 0.001). The participants in the lowest adiponectin quartile had a significantly increased risk for acquiring NAFLD (OR = 2.31, 95% CI 1.72-3.15) after adjustment for potential confounders.

CONCLUSIONS

Population-based screening suggests that NAFLD is highly prevalent in middle-aged and elderly people in Shanghai, particularly among women. Serum adiponectin level is negatively associated with NAFLD independently of potential cofounders, indicating that hypoadiponectinaemia may contribute to the development of NAFLD.

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.

Prevalence of and risk factors for hepatic steatosis and nonalcoholic Fatty liver disease in people with type 2 diabetes: the Edinburgh Type 2 Diabetes Study

OBJECTIVE

Type 2 diabetes is an established risk factor for development of hepatic steatosis and nonalcoholic fatty liver disease (NAFLD). We aimed to determine the prevalence and clinical correlates of these conditions in a large cohort of people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 939 participants, aged 61-76 years, from the Edinburgh Type 2 Diabetes Study (ET2DS)-a large, randomly selected population of people with type 2 diabetes-underwent liver ultrasonography. Ultrasound gradings of steatosis were compared with magnetic resonance spectroscopy in a subgroup. NAFLD was defined as hepatic steatosis in the absence of a secondary cause (screened by questionnaire assessing alcohol and hepatotoxic medication use, plasma hepatitis serology, autoantibodies and ferritin, and record linkage to determine prior diagnoses of liver disease). Binary logistic regression was used to analyze independent associations of characteristics with NAFLD.

RESULTS

Hepatic steatosis was present in 56.9% of participants. After excluding those with a secondary cause for steatosis, the prevalence of NAFLD in the study population was 42.6%. Independent predictors of NAFLD were BMI, lesser duration of diabetes, HbA(1c), triglycerides, and metformin use. These remained unchanged after exclusion of participants with evidence of hepatic fibrosis from the group with no hepatic steatosis.

CONCLUSIONS

Prevalences of hepatic steatosis and NAFLD were high in this unselected population of older people with type 2 diabetes, but lower than in studies in which ultrasound gradings were not compared with a gold standard. Associations with features of the metabolic syndrome could be used to target screening for this condition.

Noninvasive quantification of pancreatic fat in healthy male population using chemical shift magnetic resonance imaging: effect of aging on pancreatic fat content

OBJECTIVES

This study was aimed to establish a database of pancreatic fat fractions for healthy men aged 20 to 70 years using double-echo chemical shift gradient-echo magnetic resonance imaging.

METHODS

The double-echo chemical shift gradient-echo magnetic resonance imaging technique was used in this study. A phantom of fat-water mixtures was established to test the accuracy of the sequence. In addition, 126 healthy male volunteers (20-70 years, body mass index ≤ 25) were enrolled. Fat content of the pancreas (head, body, and tail) was examined.

RESULTS

On the phantom, a significant positive linear correlation and linear regression was found between the calculated and actual fat fractions of fat emulsions. For volunteers, there was no significant difference regarding fat fractions among the 3 regions of pancreata in each age group (P > 0.05). Pancreatic fat fraction (6.32% ± 1.18%) of healthy men aged 50 to 70 years was approximately 1-fold higher than that (2.8% ± 0.66%) of those aged 20 to 50 years (P < 0.01).

CONCLUSIONS

Double-echo chemical shift gradient-echo magnetic resonance imaging is useful for quantifying pancreatic fat fraction. This noninvasive technique has revealed (1) an even distribution of pancreatic fat in healthy men, (2) aging as an independent risk factor for pancreatic steatosis, and (3) the increase in pancreatic fat fraction beginning in the fifth decade.

[Fatty liver and its clinical management in obese adolescents]

Liver steatosis, also called non-alcoholic fatty liver, is characterized by a pathological fat accumulation in the liver, leading to liver damage in the form of inflammation and fibrosis. These histological features are similar to those in alcoholic hepatitis. Obesity is known to be the most common cause of simple steatosis in the preadolescent and adolescent population with a consequent serious health risk. The aim of this study was to provide an update on the concepts, pathophysiology and clinical management of hepatic steatosis secondary to obesity at an early age.

Noninvasive investigations for non alcoholic fatty liver disease and liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) includes a spectrum of diseases that have insulin resistance in common and are associated with metabolic conditions such as obesity, type 2 diabetes mellitus, and dyslipidemia. NAFLD ranges from simple liver steatosis, which follows a benign course, to nonalcoholic steatohepatitis (NASH), a more severe entity, with necroinflammation and fibrosis, which can progress to cryptogenic cirrhosis and end-stage liver disease. Liver biopsy remains the gold standard for evaluating the degree of hepatic necroinflammation and fibrosis; however, several noninvasive investigations, such as serum biomarkers, have been developed to establish the diagnosis and also to evaluate treatment response. These markers are currently neither available in all centers nor validated in extensive studies. Examples include high-sensitivity C reactive protein and plasma pentraxin 3, which are associated with extensive liver fibrosis in NASH. Interleukin-6 correlates with inflammation, and cytokeratin-18 represents a marker of hepatocyte apoptosis (prominent in NASH and absent in simple steatosis). Tissue polypeptide specific antigen seems to have a clinical utility in the follow-up of obese patients with NASH.

Downregulation of ADIPOQ and PPARγ2 gene expression in subcutaneous adipose tissue of obese adolescents with hepatic steatosis

Hepatic steatosis is associated with hypoadiponectinemia. The mechanism(s) resulting in lower serum adiponectin levels in obese adolescents with fatty liver is unknown. In two groups of equally obese adolescents, but discordant for hepatic fat content, we measured adiponectin, leptin, peroxisome proliferator-activated receptor γ 2 (PPARγ2) and tumor necrosis factor-α (TNFα) gene expression in the abdominal subcutaneous adipose tissue (SAT). Twenty six adolescents with similar degrees of obesity underwent a subcutaneous periumbilical adipose tissue biopsy, in addition to metabolic (oral glucose tolerance test, and hyperinsulinemic--euglycemic clamp), and imaging studies (magnetic resonance imaging (MRI), DEXA). Using quantitative real-time-PCR; adiponectin, PPARγ2, TNFα, and leptin mRNA were measured. Based on a hepatic fat content (hepatic fat fraction, HFF) >5.5%, measured by fast MRI, the subjects were divided into low and high HFF group. In addition to the hypoadiponectinemia in the high HFF group, we found that the expression of adiponectin as well as PPARγ2 in the SAT was significantly decreased in this group. No differences were noted for TNFα and leptin plasma or mRNA levels between the groups. An inverse relationship was observed between adiponectin or PPARγ2 expression and hepatic fat content, whereas, adiponectin expression was positively related to PPARγ2 expression. Independent of overall obesity, a reduced expression of adiponectin and PPARγ2 in the abdominal SAT is associated with high liver fat content, as well as with insulin resistance in obese adolescents.

Ethnic differences in lipoprotein subclasses in obese adolescents: importance of liver and intraabdominal fat accretion

BACKGROUND

Recently, the deleterious metabolic effects of visceral fat [visceral adipose tissue (VAT)] deposition were challenged, and liver fat emerged as having a key independent role in the modulation of cardiometabolic risk factors.

OBJECTIVE

We explored the relation between liver fat content and VAT in 3 ethnic groups and evaluated whether the ethnic differences in the distributions of lipoprotein concentrations and sizes were associated with the hepatic fat fraction (HFF), VAT, or both.

DESIGN

In a multiethnic group of 33 white, 33 African American, and 33 Hispanic obese adolescents with normal glucose tolerance, we measured VAT and HFF by using magnetic resonance imaging. Fasting lipoprotein particle number and size were measured by using nuclear magnetic resonance spectroscopy. To assess the association between VAT and HFF, we categorized VAT into tertiles.

RESULTS

In each ethnic group, HFF values increased between successive tertiles of VAT. After multivariate adjustment and in comparison with the 2 other groups, African Americans showed lower triglyceride (P = 0.001) and higher HDL (P = 0.03) concentrations, lower concentrations of total (P = 0.007), large (P = 0.005), and medium (P lt 0.0001) VLDL, but higher concentrations of large HDL particles (P = 0.01) and larger HDL (P = 0.005). In multivariate linear models, independent of ethnicity, VAT was a significant predictor for large HDL (P = 0.003) and total small LDL (P = 0.001) concentrations, whereas HFF significantly predicted large VLDL (P = 0.03) concentrations.

CONCLUSION

Liver fat accretion, independent of VAT, may play a role in the ethnic differences seen in large VLDL particles. This trial was registered at clinicaltrials.gov as NCT00536250.

Liver fat change in obese children after a 1-year nutrition-behavior intervention

OBJECTIVES

To evaluate whether a 1-year nutrition-behavior intervention based on normocaloric balanced diet and physical exercise may reduce liver fat in obese children.

PATIENTS AND METHODS

Twenty-six obese children (11 boys and 15 girls), aged 6 to 14 years, underwent anthropometric, nutritional, metabolic, and liver magnetic resonance imaging (MRI) examinations at baseline and after a 1-year nutrition-behavior intervention. Anthropometry included weight, height, waist and hip circumference, and total upper arm area. Body mass index z scores were calculated. Biochemistry included serum aminotransferases, lipid profile, glucose, and insulin. Liver steatosis was judged as hepatic fat fraction (FF) by MRI and was > or =9%.

RESULTS

Prevalence of steatosis was 34.6% at baseline and declined to 7.7% after intervention (P < 0.0001). Mean (95% CI) reduction of liver FF was 8.0% (4.0%-12.0%). In 77.8% of children with liver steatosis at baseline, the FF declined lower than 9% at the end of intervention, going from a mean (SD) of 18.7% (9.1) to 1.3% (4.1), (P < 0.0001). At the end of the intervention, children showed a mean reduction in body mass index z score of 0.26 (0.11-0.41) and waist circumference of 1.46 (0.34-2.60) cm. Triglycerides, total cholesterol, apolipoprotein A1, apolipoprotein B, ApoA1/ApoB ratio, and gamma-glutamyltransferase plasma values in plasma decreased at the end of intervention (P < 0.05).

CONCLUSIONS

The results suggest that in obese children nutritional-behavior interventions may reduce the liver fat.

Pediatric nonalcoholic fatty liver disease: A clinical and laboratory challenge

The true prevalence of pediatric nonalcoholic fatty liver disease (NAFLD) is unknown. Challenges in determining the population prevalence of NAFLD include the type of test (and the reference intervals used to define normal and abnormal), the type of population (general population, hospital series), the demographic characteristics of the population sampled, and the nature of the study design. The natural history of pediatric NAFLD remains uncertain. The issue of when to perform a liver biopsy in children with suspected NAFLD remains controversial. Children with NAFLD but normal alanine aminotransferase are rarely investigated. However, evidence of alterations in glucose metabolism parameters should prompt a better understanding of the natural history of pediatric NAFLD not only in terms of the progression of liver disease but also regarding its potential relationship with other health outcomes such as type 2 diabetes mellitus and cardiovascular disease. This evidence could make liver biopsy mandatory in the majority of cases at risk of progressive and severe hepatic and extrahepatic disease. This conclusion, however, raises the question of the feasibility of liver biopsy assessment in an extremely large at risk population, and of the cost/effectiveness of this policy. There is a considerable, continuous interest in reliable, noninvasive alternatives that will allow the prognosis of pediatric NAFLD to be followed in large community or population-based studies.

Assessment of hepatic steatosis in patients undergoing liver resection: comparison of US, CT, T1-weighted dual-echo MR imaging, and point-resolved 1H MR spectroscopy

PURPOSE

To compare the diagnostic performance of ultrasonography (US), computed tomography (CT), T1-weighted dual-echo magnetic resonance (MR) imaging, and point-resolved proton (hydrogen 1[(1)H]) MR spectroscopy in the assessment of hepatic steatosis in patients undergoing liver resection.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board, and patients gave written informed consent. US, CT, T1-weighted MR imaging, and (1)H MR spectroscopy were performed preoperatively in 46 patients. Imaging results were correlated (Spearman correlation coefficient) with histopathologic analysis of results of intraoperative liver biopsies. To assess differences between groups, one-way analysis of variance was used. Sensitivity and specificity were calculated for each imaging modality by using receiver operating characteristic curve analysis, with a histopathologic cut-off value of 5% macrovesicular steatosis. Differences in sensitivity and specificity were assessed by means of McNemar analysis.

RESULTS

At histopathologic examination, 23 patients had no (0%-5%) macrovesicular steatosis, 11 had mild (5%-33%), nine had moderate (33%-66%), and three had severe (>66%). MR imaging and (1)H MR spectroscopic measurements of hepatic fat had stronger correlation with histopathologic steatosis assessment (r = 0.85, P < .001 and r = 0.86, P < .001, respectively) than did US (r = 0.66, P < .001) and CT (r = -0.55, P < .001). Only T1-weighted MR imaging and (1)H MR spectroscopy showed differences across steatosis grades: none versus mild (P = .001 for both), mild versus moderate (P < .001 for both), and moderate versus severe (P = .04 and .01, respectively). Sensitivity of US, CT, T1-weighted MR imaging, and (1)H MR spectroscopy was 65% (13 of 20), 74% (17 of 23), 90% (19 of 21), and 91% (21 of 23), respectively, and specificity was 77% (17 of 23), 70% (14 of 20), 91% (20 of 22), and 87% (20 of 23), respectively.

CONCLUSION

In contrast to US and CT, T1-weighted MR imaging and (1)H MR spectroscopy strongly correlate with histopathologic steatosis assessment and are able to demonstrate differences across steatosis grades. T1-weighted dual-echo MR imaging and (1)H MR spectroscopy had the best diagnostic accuracy in depicting hepatic steatosis.

Risk factors for liver steatosis in obese children and adolescents

BACKGROUND

Concurrent with the recent rise of the incidence in obesity, nonalcoholic fatty liver disease is increasingly prevalent in childhood. The aim of this study was to identify non-invasive biomarkers for liver steatosis in obese children and adolescents.

METHODS

We used a cross-sectional study to examine risk factors for liver steatosis in obese children and adolescents. Sixty-nine obese subjects aged 6-17 years were recruited. The diagnosis of liver steatosis was made by liver ultrasonography. Anthropometric, serum biochemical variables, and oral glucose tolerance tests were measured.

RESULTS

Thirty-eight (55.1%) subjects had liver steatosis. Elevated alanine aminotransferase levels (> 30 IU/L in boys and >19 IU/L in girls) were found in 27 (71.1%) of the 38 subjects with liver steatosis. In multivariate logistic regression analysis, liver steatosis was associated with waist circumference and the change of plasma glucose level before and after oral glucose tolerance testing (C-OGTT). For every 5 cm increase in waist circumference, there was an odds ratio of 1.391 for predicting liver steatosis (95% confidence interval: 1.009-1.916, p = 0.044). C-OGTT was the only laboratory variable that independently predicted liver steatosis, with an odds ratio of 1.198 (95% confidence interval: 1.022-1.404, p = 0.026) for each 5 mg/dL of increase.

CONCLUSION

In this hospital-based sample of obese children and adolescents, liver steatosis was common. Liver steatosis was positively associated waist circumference and C-OGTT. These findings have implications for screening liver steatosis in obese children and adolescents.

Proton magnetic resonance spectroscopy and ultrasound for hepatic fat quantification

AIM

The increasing prevalence of fatty liver disease requires routine assessment methods. Proton magnetic resonance spectroscopy ((1)H MRS) is increasingly used for steatosis measurement, but due to cost, is unlikely to become a widely-used screening tool. Ultrasound is cheaper and more widely available, although subject to observer variability. Our aim was to determine the sensitivity and specificity of ultrasound against (1)H MRS, using MRS as a gold standard, for the detection and quantification of hepatic fat content.

METHODS

Fifty adults participated (43 men, seven women) in this study. Hepatic steatosis was assessed by ultrasound and (1)H MRS. Images were graded by two independent radiologists to classify severity and distribution of liver fat.

RESULTS

Ultrasound detected liver fat infiltration in 82% of cases measurable by (1)H MRS, while liver fat was detectable in 44% of cases graded absent by ultrasound. Ultrasound grading was subjective, with the radiologists in agreement in 53% of cases (kappa = 0.39, P = 0.002). Considerable overlap in intrahepatocellular lipid content was observed between different grades: absent (0.0-1.58%), mild (2.2-16.2%), moderate (4.9-26.7%) and severe (8.1-76.8%) steatosis. Ultrasound could not detect liver fat levels below 2% as measured by (1)H MRS Conclusion: Ultrasound is less sensitive than (1)H MRS in detecting very low levels of liver fat content, but is sensitive to fatty infiltration greater than 2%. There is a tendency of higher ultrasound grades to correlate with higher degrees of fatty infiltration, although some overlap exists. Our findings are still consistent with ultrasound being useful as a low cost screening tool.

MRI of the liver--how to do it

This article details indications, patient preparation, pulse sequences/protocols, and contrast agents for pediatric hepatobiliary MRI. When performed well, MRI provides superior diagnostic information relative to CT for evaluation of hepatic tumors, liver transplants, and biliary disease.

Mipomersen, an apolipoprotein B synthesis inhibitor, for lowering of LDL cholesterol concentrations in patients with homozygous familial hypercholesterolaemia: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Homozygous familial hypercholesterolaemia is a rare genetic disorder in which both LDL-receptor alleles are defective, resulting in very high concentrations of LDL cholesterol in plasma and premature coronary artery disease. This study investigated whether an antisense inhibitor of apolipoprotein B synthesis, mipomersen, is effective and safe as an adjunctive agent to lower LDL cholesterol concentrations in patients with this disease.

METHODS

This randomised, double-blind, placebo-controlled, phase 3 study was undertaken in nine lipid clinics in seven countries. Patients aged 12 years and older with clinical diagnosis or genetic confirmation of homozygous familial hypercholesterolaemia, who were already receiving the maximum tolerated dose of a lipid-lowering drug, were randomly assigned to mipomersen 200 mg subcutaneously every week or placebo for 26 weeks. Randomisation was computer generated and stratified by weight (<50 kg vs >/=50 kg) in a centralised blocked randomisation, implemented with a computerised interactive voice response system. All clinical, medical, and pharmacy personnel, and patients were masked to treatment allocation. The primary endpoint was percentage change in LDL cholesterol concentration from baseline. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00607373.

FINDINGS

34 patients were assigned to mipomersen and 17 to placebo; data for all patients were analysed. 45 patients completed the 26-week treatment period (28 mipomersen, 17 placebo). Mean concentrations of LDL cholesterol at baseline were 11.4 mmol/L (SD 3.6) in the mipomersen group and 10.4 mmol/L (3.7) in the placebo group. The mean percentage change in LDL cholesterol concentration was significantly greater with mipomersen (-24.7%, 95% CI -31.6 to -17.7) than with placebo (-3.3%, -12.1 to 5.5; p=0.0003). The most common adverse events were injection-site reactions (26 [76%] patients in mipomersen group vs four [24%] in placebo group). Four (12%) patients in the mipomersen group but none in the placebo group had increases in concentrations of alanine aminotransferase of three times or more the upper limit of normal.

INTERPRETATION

Inhibition of apolipoprotein B synthesis by mipomersen represents a novel, effective therapy to reduce LDL cholesterol concentrations in patients with homozygous familial hypercholesterolaemia who are already receiving lipid-lowering drugs, including high-dose statins.

FUNDING

ISIS Pharmaceuticals and Genzyme Corporation.

Nonalcoholic fatty liver disease: a review and update

The spectrum of nonalcoholic fatty liver disease (NAFLD) ranges from asymptomatic steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Hepatic steatosis occurs when free fatty acids, released in the setting of insulin resistance and the metabolic syndrome, are taken up by the liver. Additional biochemical insults, including oxidative stress, upregulation of inflammatory mediators, and dysregulated apoptosis, can result in inflammation (producing NASH) and fibrosis. Noninvasive methods (e.g., abdominal ultrasonography) are safe ways to support a diagnosis of hepatic steatosis, but advanced liver histopathologic findings including NASH and fibrosis cannot be identified without pursuing liver biopsy. Recent advances in serologic and imaging methods aim to determine severity of inflammation and fibrosis noninvasively. Currently, therapeutic options for NAFLD are limited to medications that reduce risk factors, but the future holds promise for therapies that might slow the progression of this increasingly prevalent disorder.