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

Fatty liver disease in children: eat now pay later

INTRODUCTION

With the recent epidemic in childhood obesity, nonalcoholic fatty liver disease (NAFLD) has become an emerging problem and a common cause of chronic liver disease in children.

METHODS

In this review, the most recent insights on the pathogenesis, diagnosis, natural history, and treatment of NAFLD in children are discussed.

T1 independent, T2* corrected MRI with accurate spectral modeling for quantification of fat: validation in a fat-water-SPIO phantom

PURPOSE

To validate a T(1)-independent, T(2)*-corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat-water-SPIO phantom over physiologically expected ranges of fat percentage and T(2)* decay in the presence of iron overload.

MATERIALS AND METHODS

A homogeneous gel phantom consisting of vials with known fat-fractions and iron concentrations is described. Fat-fraction imaging was performed using a multiecho chemical shift-based fat-water separation method (IDEAL), and various reconstructions were performed to determine the impact of T(2)* correction and accurate spectral modeling. Conventional two-point Dixon (in-phase/out-of-phase) imaging and MR spectroscopy were performed for comparison with known fat-fractions.

RESULTS

The best agreement with known fat-fractions over the full range of iron concentrations was found when T(2)* correction and accurate spectral modeling were used. Conventional two-point Dixon imaging grossly underestimated fat-fraction for all T(2)* values, but particularly at higher iron concentrations.

CONCLUSION

This work demonstrates the necessity of T(2)* correction and accurate spectral modeling of fat to accurately quantify fat using MRI.

Validity of real time ultrasound in the diagnosis of hepatic steatosis: a prospective study

BACKGROUND/AIMS

Ultrasound is used to screen for hepatic steatosis, the most common liver disease in the United States. However, few studies have prospectively evaluated the accuracy of ultrasound to diagnose hepatic steatosis. Therefore, a double blinded prospective study was performed in consecutive patients undergoing liver biopsy to evaluate the accuracy of ultrasound to diagnose hepatic steatosis.

METHODS

Real time ultrasound was performed just prior to the biopsy by a single investigator masked to the clinical diagnosis. The liver biopsy was reviewed by a pathologist masked to the clinical indication or sonographic findings.

RESULTS

Of 73 consecutive patients studied, macrovesicular steatosis of any severity on biopsy was found in 46 (63%) and micro vesicular fat found in 51 (69.9%). The overall impression of the sonographer for the presence of macrovesicular hepatic steatosis of any degree had a sensitivity of 60.9% and a specificity of 100%. The sensitivity increased to 100% and the specificity to 90% when there was > or =20% of fat. The zonular distribution of the fat did not alter the diagnostic accuracy of ultrasound. Ultrasound had a poor yield in the diagnosis of microvesicular fat with an overall sensitivity of 43% and a specificity of 73%. The combination of increased echogenicity and portal vein blurring on ultrasound had the greatest sensitivity in the diagnosis of hepatic steatosis.

CONCLUSION

Real time ultrasound using a combination of sonographic findings has a high specificity but underestimates the prevalence of hepatic steatosis when there is<20% fat.

The value of transabdominal ultrasound for assessment of the severity of liver steatosis as compared to liver biopsy

The purpose of our paper was to evaluate the performance of ultrasound (US) for assessment of the severity of liver steatosis as compared to a pathological examination, which is presently considered to be the gold standard, in patients that have undergone liver biopsy for various reasons. We performed echo-assisted liver biopsy in 161 patients with chronic hepatitis with the US aspect of “bright liver” with “posterior attenuation”, using modified Menghini needles. Following the US examination, the severity of liver steatosis was estimated as minimal, mild, moderate. or severe according to the Hepburn classification: absent (affecting 0% to 2% of the hepatocytes), minimal (2% to 10%), mild (10% to 30%), moderate (30% to 60%), and severe (more than 60% of the hepatocytes). The results of this study showed that the sensitivity of US for the prediction of histological steatosis of at least moderate severity was 0.64, with 0.77 specificity, 0.55 positive predictive value, and 0.94 negative predictive value. The overall accuracy was 0.75. This study showed that the transabdominal ultrasound evaluation of the fatty liver is a quite good predictor, perhaps sufficient for most purposes, for the estimation of the severity of liver steatosis in the moderate to severe range.

Quantitative estimation of the degree of hepatic macrovesicular steatosis in a disease-free population: a single-center experience in mainland China

The aim of this study was to derive a simple equation to enable the extent of hepatic macrovesicular steatosis (HMS) to be predicted quantitatively from data obtained noninvasively and hence avoid unnecessary liver biopsies. One hundred sixty-seven potential living liver donors and 45 subjects suspected of having nonalcoholic fatty liver disease (NAFLD) underwent percutaneous liver biopsy to evaluate HMS quantitatively. Their hepatic unenhanced computed tomography (CT) attenuation, body mass index (BMI), and indices of serum lipids were reviewed. Logistic regression analysis was undertaken to screen for independent predictors of HMS. Linear regression analysis was then used to plot the relationship between the severity of histologically confirmed HMS and identified independent predictors of HMS. For potential donors with HMS of severity > or = 5% by histological assessment, the following equation was derived: HMS = 47.7 + 1.48BMI - 1.14CT (R2 = 0.74)The calculated HMS for potential donors with histologically confirmed HMS of severity < 5% seemed to be unreliable (R(2) = = 0.230, P < 0.3). In addition, in subjects suspected of having NAFLD, there was a close agreement between values for histologically confirmed HMS and calculated values for HMS derived from the equation (intraclass correlation coefficient = 0.88). Hepatic CT imaging in conjunction with other noninvasive clinical data may enable the extent of HMS to be accurately predicted with the equation derived from potential donors with appreciable degrees of histologically confirmed HMS.

Nonalcoholic fatty liver disease in children living in the obeseogenic society

BACKGROUND

The problem of obesity in children has grown considerably in recent years in the United States as well as the rest of the world. This has resulted in a marked increase in the prevalence of nonalcoholic liver disease in the pediatric age group. Nonalcoholic fatty liver disease (NAFLD) is currently the most common hepatic disorder seen in pediatric hepatology practice.

DATA SOURCES

We have reviewed the most recent literature regarding the prevalence, pathogenesis as well as the most recent advances in the diagnostic and therapeutic modalities of NAFLD in children.

RESULTS

NAFLD affects a substantial portion of the population including children.

CONCLUSIONS

The rising incidence of NAFLD, nonalcoholic steatohepatitis (NASH) and cirrhosis emphasizes the need for effective treatment options. The lack of complete understanding of the pathogenesis of NAFLD still limits our ability to develop novel therapeutic modalities that can target the metabolic derangements implicated in the development of the disorder.

Imaging-based quantification of hepatic fat: methods and clinical applications

Fatty liver disease comprises a spectrum of conditions (simple hepatic steatosis, steatohepatitis with inflammatory changes, and end-stage liver disease with fibrosis and cirrhosis). Hepatic steatosis is often associated with diabetes and obesity and may be secondary to alcohol and drug use, toxins, viral infections, and metabolic diseases. Detection and quantification of liver fat have many clinical applications, and early recognition is crucial to institute appropriate management and prevent progression. Histopathologic analysis is the reference standard to detect and quantify fat in the liver, but results are vulnerable to sampling error. Moreover, it can cause morbidity and complications and cannot be repeated often enough to monitor treatment response. Imaging can be repeated regularly and allows assessment of the entire liver, thus avoiding sampling error. Selection of appropriate imaging methods demands understanding of their advantages and limitations and the suitable clinical setting. Ultrasonography is effective for detecting moderate or severe fatty infiltration but is limited by lack of interobserver reliability and intraobserver reproducibility. Computed tomography allows quantitative and qualitative evaluation and is generally highly accurate and reliable; however, the results may be confounded by hepatic parenchymal changes due to cirrhosis or depositional diseases. Magnetic resonance (MR) imaging with appropriate sequences (eg, chemical shift techniques) has similarly high sensitivity, and MR spectroscopy provides unique advantages for some applications. However, both are expensive and too complex to be used to monitor steatosis.

Gender-specific prevalences of fatty liver in obese children and adolescents: roles of body fat distribution, sex steroids, and insulin resistance

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is known to have a gender-dimorphic prevalence in obese children. Less information is available on predictive factors for NAFLD in obese youths.

OBJECTIVE

The aim of the study was to examine the prevalence pattern and to identify clinical and laboratory markers associated with the risk for NAFLD.

DESIGN

This was a cross-sectional study.

SETTING

The study setting was a rehabilitation clinic.

STUDY PARTICIPANTS

A total of 532 obese subjects (291 girls) aged 8-19 yr participated in the study.

MAIN MEASUREMENTS

Steatosis hepatis and visceral fat mass were determined by ultrasound. Laboratory tests included serum lipids, adiponectin, high-sensitivity C-reactive protein, sex steroids, and an oral glucose tolerance test.

RESULTS

Prevalence of hepatic steatosis was significantly higher in boys (41.1%) than in girls (17.2%) and was highest in postpubertal boys (51.2%) and lowest in postpubertal girls (12.2%). Severity of steatosis was associated with increased visceral fat mass, insulin resistance, lower adiponectin levels, and higher blood pressure. Three factors were extracted from the panel of investigated parameters by principal component analysis. Logistic regression analysis revealed significant associations of simple steatosis with the "insulin resistance and visceral fat" factor and the "body fat distribution and inflammation" factor in both genders and additionally with the "steroid hormones" factor in girls. Risk for steatosis hepatis with concomitantly elevated ALT was associated only with "insulin resistance and visceral fat" in girls and with all three factors in boys.

CONCLUSION

Our results suggest significant associations of NAFLD with markers of visceral obesity and insulin resistance in both genders and gender-specific associations with parameters of body fat distribution and sex steroids.

Reproducibility of 3.0 Tesla magnetic resonance spectroscopy for measuring hepatic fat content

PURPOSE

To investigate reproducibility of proton magnetic resonance spectroscopy ((1)H-MRS) to measure hepatic triglyceride content (HTGC).

MATERIALS AND METHODS

In 24 subjects, HTGC was evaluated using (1)H-MRS at 3.0 Tesla. We studied "between-weeks" reproducibility and reproducibility of (1)H-MRS in subjects with fatty liver. We also studied within liver variability and within day reproducibility. Reproducibility was assessed by coefficient of variation (CV), repeatability coefficient (RC), and intraclass correlation coefficient (ICC).

RESULTS

The CV of between weeks reproducibility was 9.5%, with a RC of 1.3% HTGC (ICC 0.998). The CV in fatty livers was 4.1%, with a RC of 1.3% HTGC (ICC 0.997). Within day CV was 4.5%, with a RC of 0.4% HTGC (ICC 0.999). CV for within liver variability was 14.5%.

CONCLUSION

Reproducibility of (1)H-MRS to measure HTGC for "between-weeks" measurements and in fatty livers is high, which is important for follow-up studies. Within liver variability displays a larger variation, meaning that liver fat is not equally distributed and during consecutive measurements the same voxel position should be used.

Methods for assessing intrahepatic fat content and steatosis

PURPOSE OF REVIEW

Intrahepatic fat content is increasingly being recognized as an integral part of metabolic dysfunction. This article reviews available methods for the assessment of hepatic steatosis.

RECENT FINDINGS

Apart from liver biopsy, there are several noninvasive radiologic modalities for evaluating nonalcoholic fatty liver disease. Ultrasonography, computed tomography, and traditional MRI remain largely qualitative methods for detecting mild to severe degrees of steatosis rather than quantitative methods for measuring liver fat content, even though novel attempts to collect objective quantitative information have recently been developed. Still, their sensitivity at mild degrees of steatosis is poor. Undoubtedly, most methodological advances have occurred in the field of MRI and magnetic resonance spectroscopy, which currently enable the accurate quantification of intrahepatic fat even at normal or near normal levels. Xenon computed tomography was also recently shown to offer another objective tool for the quantitative assessment of steatosis, although more validation studies are required.

SUMMARY

Several modalities can be used for measuring intrahepatic fat and assessing steatosis; the choice will ultimately depend on the intended use and available resources.

Non-invasive assessment and quantification of liver steatosis by ultrasound, computed tomography and magnetic resonance

Hepatic steatosis is the most prevalent liver disorder in the developed world. It is closely associated with features of metabolic syndrome, especially insulin resistance and obesity. The two most common conditions associated with fatty liver are alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Liver biopsy is considered the gold standard for the assessment of liver fat, but there is a need for less invasive diagnostic techniques. New imaging modalities are emerging, which could provide more detailed information about hepatic tissue or even replace biopsy. In the present review, available imaging modalities (ultrasound, computed tomography, magnetic resonance imaging and proton magnetic resonance spectroscopy) are presented which are employed to detect or even quantify the fat content of the liver. The advantages and disadvantages of the above-mentioned imaging modalities are discussed. Although none of these techniques is able to differentiate between microvesicular and macrovesicular steatosis and to reveal all features visible using histology, the proposed diagnostic modalities offer a wide range of additional information such as anatomical and morphological information non-invasively. In particular, magnetic resonance imaging and proton magnetic resonance spectroscopy are able to quantify the hepatic fat content hence avoiding exposure to radiation. Except for proton magnetic resonance spectroscopy, all modalities offer additional information about regional fat distribution within the liver. MR elastography, which can estimate the amount of fibrosis, also appears promising in the differentiation between simple steatosis and steatohepatitis.

Magnetic resonance imaging and spectroscopy accurately estimate the severity of steatosis provided the stage of fibrosis is considered

BACKGROUND/AIMS

Currently the diagnosis and severity of hepatic steatosis can be established accurately only by liver biopsy. Previous small studies found that steatosis measured by magnetic resonance spectroscopy (MRS) and imaging (MRI) correlated with histological assessment of liver triglyceride content. However, the accuracy of MRS/MRI for grading the severity of steatosis has not been addressed. The aims of this study were (1) to determine whether MRS and MRI can discriminate grades of steatosis in a large cohort of consecutive patients with a wide spectrum of liver disease aetiology and severity (2) to evaluate the effect of hepatic fibrosis, inflammation and iron on quantitation of intrahepatocellular lipid (IHCL) by these techniques.

METHODS

Ninety-four sequential patients who underwent percutaneous liver biopsy or liver resection had MRS and MRI (Dixon in phase/out of phase (Dixon IP/OP) and with/without fat saturation (+/-FS) images) to determine IHCL. Histology was used as the reference standard.

RESULTS

Close relationships were observed between the percentage of steatosis estimated by histology and MRS/MRI (r(s)=0.88 p<0.001 for all techniques). However, separate equations were required for the percentage of steatosis to avoid underestimation by imaging for patients with moderate or advanced fibrosis. All techniques had good diagnostic accuracy for mild steatosis (AUROC > or =0.87) as well as moderate/severe steatosis (AUROC > or =0.89). Hepatic inflammation and mild iron deposition (Perls' grade 1 and 2) did not interfere with estimation of steatosis by imaging.

CONCLUSIONS

MRS and MRI had good accuracy for grading the severity of steatosis in subjects with liver disease, provided that stage of fibrosis was considered.

Glucose dysregulation and hepatic steatosis in obese adolescents: is there a link?

Fatty liver is increasingly common in obese adolescents. We determined its association with glucose dysregulation in 118 (37M/81F) obese adolescents of similar age and percent total fat. Fast-magnetic resonance imaging (MRI) and simple MRI were used to quantify hepatic fat content and abdominal fat distribution. All subjects had a standard oral glucose tolerance test. Insulin sensitivity was estimated by the Matsuda Index and homeostasis model assessment of insulin resistance. Baseline total and high molecular weight (HMW)-adiponectin and interleukin (IL)-6 levels were measured. The cohort was stratified according to tertiles of hepatic fat content. Whereas age and %fat were comparable across tertiles, ethnicity differed in that fewer Blacks and more Whites and Hispanics were in the moderate and high category of hepatic fat fraction (HFF). Visceral and the visceral-to-subcutaneous fat ratio increased and insulin sensitivity decreased across tertiles. Two-hour plasma glucose rose with increasing hepatic steatosis (P < 0.008). 73.7% of the subjects in the high HFF had the metabolic syndrome compared to 19.5% and 30.6%, respectively, in the low and moderate categories. Both total and HMW-adiponectin decreased, and IL-6 increased with increasing hepatic steatosis.

CONCLUSION

In obese adolescents, independent of total fat, increasing severity of fatty liver is associated with glucose dysregulation, metabolic syndrome, and with a proinflammatory milieu.

Diagnostic value of a computerized hepatorenal index for sonographic quantification of liver steatosis

OBJECTIVE

Quantification of liver steatosis is clinically relevant in various liver diseases but cannot be done by conventional sonography, which only provides a qualitative assessment with significant observer variability. The aim of this study was to assess sonography as an objective tool for the quantification of liver steatosis.

MATERIALS AND METHODS

Files of 111 patients with chronic liver disease who were referred for sonographically guided liver biopsy were collected. A hepatorenal sonographic index was calculated on the basis of the ratio between the echogenicity of the liver and that of the right kidney cortex using histogram echo intensity. Liver steatosis was graded by histology.

RESULTS

A significant correlation was found between histologic steatosis and the hepatorenal sonographic index (r = 0.82, p < 0.001). The validity of the hepatorenal sonographic index for the diagnosis of fatty liver was compared with liver biopsies with a steatosis level > 5%. The area under the receiver operating characteristic curve was 99.2% (95% CI, 98-100%). The optimal hepatorenal sonographic index cutoff point for the prediction of steatosis > 5% was 1.49, with sensitivity of 100% and specificity of 91%. The optimal hepatorenal sonographic index cutoff point for the prediction of steatosis >/= 25% was 1.86, with sensitivity of 90% and specificity of 90%. The optimal hepatorenal sonographic index cutoff point for the prediction of steatosis >/= 60% was 2.23, with sensitivity of 90% and specificity of 93%.

CONCLUSION

The hepatorenal sonographic index is a sensitive noninvasive method for steatosis quantification. It can diagnose small amounts of liver fat that would be missed by conventional sonography. It is reproducible and operator independent and can serve as an efficient tool to follow patients with steatosis and evaluate the efficacy of new treatment techniques.

MRI findings in nonalcoholic steatohepatitis: correlation with histopathology and clinical staging

PURPOSE

To evaluate magnetic resonance imaging (MRI) findings of nonalcoholic steatohepatitis (NASH) and to determine the correlation of MRI findings with histopathology and Mayo End-Stage Liver Disease (MELD) score.

MATERIALS AND METHODS

Thirty patients (18 males, 12 females; mean age: 57+/-8.9 years; age range: 35-71 years) with histopathologically proven NASH who underwent MRI examinations between January 2001 and October 2005 were included in the study. Two radiologists retrospectively reviewed all magnetic resonance (MR) examinations in consensus to evaluate the presence and extent of predetermined findings of NASH including liver steatosis, early patchy liver enhancement indicating inflammation and liver fibrosis. The findings detected on MRI were correlated and compared to histopathological findings and MELD score by using nonparametric Spearman correlation coefficient and Kruskal-Wallis analysis of variance.

RESULTS

Liver steatosis was observed in 10 of 30 patients; early patchy liver enhancement, in 8 of 30 patients and liver fibrosis in 19 of 30 patients on MR images. Liver fibrosis was reticular in all these patients. There were statistically significant moderate correlations between MRI findings of liver steatosis and histopathologic grades of steatosis (r=0.43; P<.05), and between MRI findings of fibrosis and histopathologic stages of fibrosis (r=0.61; P<.001). Early patchy enhancement did not demonstrate statistically significant correlation with inflammation (P=.28). There was no statistically significant overall correlation between MRI findings of NASH and MELD score.

CONCLUSION

MRI findings of liver steatosis and fibrosis in NASH showed moderate correlations with histopathologic grades of steatosis and stages of fibrosis, but MRI findings of NASH did not demonstrate any significant correlations with MELD score.

Noninvasive assessment of hepatic steatosis

Hepatic steatosis, the accumulation of lipids within hepatocytes, is a common condition. The prevalence of its most frequent manifestation, nonalcoholic fatty liver disease (NAFLD), has been estimated to be as high as 35% in some populations. Currently, liver biopsy is the gold standard for the diagnosis and assessment of severity of hepatic steatosis, staging of fibrosis, and is the only modality able to differentiate bland steatosis from steatohepatitis. However, its invasiveness, significant side effect profile, and susceptibility to sampling error ultimately make it a suboptimal tool. Accordingly, focus has been placed on noninvasive radiologic techniques for hepatic fat detection and quantification. The rationale, performance characteristics, and limitations of traditional noninvasive measures, including ultrasound, computed tomography, and magnetic resonance (MR) spectroscopy and imaging, are reviewed. A novel MR method, the spectrally modeled relaxation-invariant technique, overcomes the inherent weaknesses of conventional MR to diagnose and quantify hepatic steatosis over its entire range of severity. Noninvasive radiologic techniques, particularly MR, can be applied broadly, including in the diagnosis of NAFLD in asymptomatic patients with elevated serum aminotransferase levels, longitudinal monitoring of disease progression or response to treatment, population-based epidemiologic or observational studies, and drug discovery.

MRI in identifying hepatic steatosis in obese children and relation to ultrasonography and metabolic findings

OBJECTIVES

The aim of this study was to identify nonalcoholic fatty liver in obese children by magnetic resonance imaging (MRI) and to compare the findings with the data from ultrasonography and from clinical and laboratory testing.

PATIENTS AND METHODS

Sixty obese children, 6 to 14 years old, underwent hepatic MRI and abdominal ultrasonography. Biochemistry determinations included serum aminotransferases, lipid profile, glucose, and insulin. Anthropometry included body mass index, total and trunk fat, and fat-free mass obtained by dual-energy radiographic absorptiometry. Hepatic steatosis, judged as hepatic fat fraction by MRI, was >or=9%.

RESULTS

By MRI, 14 (23%) children had hepatic steatosis; of those, 5 had a fat fraction of 9% to 18%, and 9 had a fat fraction >18%. At univariate analysis, fat fraction was positively associated with being male, serum alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyltransferase, body mass index z score, insulin, systolic pressure, and total and trunk fat mass. Hepatic steatosis was independently associated with alanine aminotransferase (P < 0.01). Overall, liver echogenicity on ultrasonography correlated well with fat fraction by MRI (correlation coefficient 0.527, P < 0.0001). Among the 27 children with increased liver echogenicity, 13 (48%) had hepatic fat fraction >or=9%, and 89% of children with echogenicity graded 2 or 3 had fat fraction >18%. All of the children (n = 9) with fat fraction >18% had increased liver echogenicity, and in 8 of them it was graded 2 or 3, but the MRI fat fraction ranged greatly (28%-45%).

CONCLUSIONS

In obese children, nonalcoholic hepatic steatosis may be associated with the metabolic syndrome. Ultrasonography may be valuable in identifying high hepatic fat accumulation, but its ability to identify lower fat accumulation in the liver is scanty compared with MRI.

Non-invasive means of measuring hepatic fat content

Hepatic steatosis affects 20% to 30% of the general adult population in the western world. Currently, the technique of choice for determining hepatic fat deposition and the stage of fibrosis is liver biopsy. However, it is an invasive procedure and its use is limited, particularly in children. It may also be subject to sampling error. Non-invasive techniques such as ultrasound, Computerized tomography (CT), magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (¹H MRS) can detect hepatic steatosis, but currently cannot distinguish between simple steatosis and steatohepatitis, or stage the degree of fibrosis accurately. Ultrasound is widely used to detect hepatic steatosis, but its sensitivity is reduced in the morbidly obese and also in those with small amounts of fatty infiltration. It has been used to grade hepatic fat content, but this is subjective. CT can detect hepatic steatosis, but exposes subjects to ionizing radiation, thus limiting its use in longitudinal studies and in children. Recently, magnetic resonance (MR) techniques using chemical shift imaging have provided a quantitative assessment of the degree of hepatic fatty infiltration, which correlates well with liver biopsy results in the same patients. Similarly, in vivo¹H MRS is a fast, safe, non-invasive method for the quantification of intrahepatocellular lipid (IHCL) levels. Both techniques will be useful tools in future longitudinal clinical studies, either in examining the natural history of conditions causing hepatic steatosis (e.g. non-alcoholic fatty liver disease), or in testing new treatments for these conditions.

The accuracy of sonography in predicting steatosis and fibrosis in chronic hepatitis C

The accuracy and clinical significance of sonography (US) in demonstrating fatty liver and hepatic fibrosis in chronic hepatitis C (CHC) are rarely reported. US had sensitivity 71.1%, specificity 72.9%, 58.7% positive predictive value (PPV), and 82.3% negative predictive value (NPV) in demonstrating histological steatosis > or =5%. US had sensitivity 85.7%, specificity 60.4%, 13% PPV, and 98.4% NPV in demonstrating histological steatosis > or =30% with clinical significance in predicting prognosis and therapeutic response in CHC. Subjects with fatty liver on US had a greater prevalence of body mass index (BMI) > or =25 kg/m2, inflammation-necrosis grade >2, and total bilirubin <1.2 mg/dl in multivariate analyses. US had sensitivity 27.4%, specificity 62.5%, 71.9% PPV, and 19.7% NPV in demonstrating histological fibrosis of stage II or above, and sensitivity 13.6%, specificity 66.3%, 9.4% PPV, and 75.0% NPV in demonstrating fibrosis of stage III or above. There was no correlation between fibrotic sonographic patterns and histological stage of fibrosis (r = -0.167, P = 0.083). Besides hepatic steatosis, clinicians should be alert to the possibility of advanced necrosis-inflammation grade in interpreting a report of bright liver on gray-scale US. Gray-scale US cannot replace liver biopsy as the optimal diagnostic procedure for the prediction of hepatic steatosis and fibrosis prior to initiating therapy for CHC.

Nonalcoholic fatty liver disease

OBJECTIVE

The inflammatory subtype of nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, is becoming one of the most important causes of chronic liver disease. In this article, we discuss the epidemiology, pathogenesis, and clinical and radiologic diagnosis of the subtypes of nonalcoholic fatty liver disease.

CONCLUSION

We discuss the current and evolving imaging tests in the evaluation of hepatic fatty content, inflammation, and fibrosis.

Nonalcoholic fatty liver disease: An overview of current insights in pathogenesis, diagnosis and treatment

Estimates of people suffering from overweight (one billion) and obesity (300 million) are increasing. The accumulation of triglycerides in the liver, in the absence of excess alcohol intake, has been described in the early sixties. It was not until 1980, however, that Ludwig et al named this condition nonalcoholic steatohepatitis (NASH). Subsequently, nonalcoholic fatty liver disease (NAFLD) has been used as a general name for conditions ranging from simple steatosis through steatohepatitis to end-stage liver disease (cirrhosis). Many studies have demonstrated the significant correlation with obesity and insulin resistance. Other studies have revealed a significant correlation between hepatic steatosis, cardiovascular disease and increased intima-media thickness. WHO estimated that at least two million patients will develop cirrhosis due to hepatic steatosis in the years to come. Longitudinal cohort studies have demonstrated that those patients with cirrhosis have a similar risk to develop hepatocellular carcinoma as those with other causes of cirrhosis. Taken all together, NAFLD has become the third most important indication for liver transplantation. Therefore, training programmes in internal medicine, gastroenterology and hepatology should stress the importance of diagnosing this entity and treat properly those at risk for developing complications of portal hypertension and concomittant cardiovascular disease. This review will focus on the clinical characteristics, pathophysiology, imaging techniques and the readily available therapeutic options.

Liver steatosis in obese prepubertal children: a possible role of insulin resistance

OBJECTIVE

To determine whether in obese prepubertal children insulin resistance (IR) is associated with the development of liver steatosis.

METHODS AND PROCEDURES

Cross-sectional study evaluating the prevalence of liver steatosis in 100 severely obese prepubertal children and comparing IR indexes between children with (group 1) and without steatosis (group 2). Furthermore, IR indexes were compared to values of 50 normal weight children. Fasting blood samples were collected for the evaluation of liver function tests, lipid profile, plasma glucose, and insulin levels. All children underwent an oral glucose tolerance test and anthropometric measurements. Hepatic ultrasound was performed according to international criteria and by one single operator. Analysis was performed by Mann-Whitney U-test, Pearson correlation, and logistic regression.

RESULTS

Liver steatosis was found in 52% obese children and was equally distributed between the two sexes. Obese children were more insulin resistant when compared to controls (homeostasis model assessment of IR (HOMA-IR): P = 0.0001; whole body insulin sensitivity index (WBISI): P = 0.0005; fasting glucose/fasting insulin ratio (G/I): P = 0.0001), and group 1 presented an even higher degree of IR when compared to group 2 (HOMA-IR P = 0.0001; WBISI P = 0.0004; G/I P = 0.0001). The area under the curve (AUC) for insulin was significantly higher in group 1 when compared to group 2, while no difference was found in the AUC for glucose. There was no association between IR and adiposity indexes (P >0.05). The role of IR as a predictor for the development of steatosis was analyzed by multiple logistic regression, which documented that IR indexes were significantly related to steatosis independently of BMI-SDS.

DISCUSSION

Liver steatosis is an emerging problem in prepubertal severely obese children, and it appears to be an association between liver steatosis and IR in these subjects.

Effects of diffuse fatty infiltration of the liver on portal vein flow hemodynamics

PURPOSE

To investigate the effects of various degrees of diffuse fatty infiltration of the liver on portal vein blood flow with Doppler sonography.

METHODS

One hundred forty subjects were examined with color and spectral Doppler sonography. The subjects were divided into 4 groups of 35 subjects each according to the degree (normal, grade 1, grade 2 and grade 3) of hepatic fatty infiltration assessed on gray-scale images. The portal vein pulsatility index (VPI) and time-averaged mean flow velocity (MFV) were calculated for each subject. VPI was calculated as (peak maximum velocity - peak minimum velocity) / peak maximum velocity.

RESULTS

VPI and MFV values were, respectively, 0.32 +/- 0.06 and 16.8 +/- 2.6 cm/second in the normal group, 0.27 +/- 0.07 and 14.2 +/- 2.2 cm/second in the group with grade 1 fatty infiltration, 0.22 +/- 0.06 and 12.2 +/- 1.8 cm/second in the group with grade 2 fatty infiltration, and 0.18 +/- 0.04 and 10.8 +/- 1.5 cm/second in the group with grade 3 fatty infiltration. There was a negative inverse correlation between the grade of fatty infiltration and both VPI (f = 55.3, p < 0.001) and MFV (f = 43.9, p < 0.001).

CONCLUSION

The pulsatility index and mean velocity of the portal vein blood flow decrease as the severity of fatty infiltration increases.

Nonalcoholic fatty liver disease: from clinical recognition to treatment

Nonalcoholic fatty liver disease (NAFLD) is probably the most common spectrum of metabolic liver disease in the world, encompassing simple steatosis to steatohepatitis, advanced fibrosis, cirrhosis and hepatocellular carcinoma. NAFLD affects a significant part of the general population worldwide. The existing correlation between obesity and NAFLD in combination with the increase in the frequency of obesity in the developed world implies that the incidence and severity of NAFLD will increase in the near future. Newer data support the idea that NAFLD constitutes the more important cause of cryptogenic cirrhosis of the liver and a ground for the development of hepatocellular carcinoma. Liver biopsy remains the most specific and sensitive method to differentiate NAFLD, providing important information on the long-term prognosis of the patients. The 'two hit' hypothesis constitutes the currently prevailing theory for the development of NAFLD and nonalcoholic steatohepatitis. The first 'hit' is purported to be the increase of free fatty acids in hepatocytes, which results in a decrease of beta-oxidation. The second step includes all mechanisms contributing to the development of necroinflammation and fibrosis. Currently, an effective treatment for patients with NAFLD does not exist. Improvement in liver histology remains the primary goal of any therapeutic approach in patients with NAFLD. Viewing NAFLD in the frame of the metabolic syndrome opens the possibility that both the onset of the disease and disease progression could be prevented by changes in lifestyle. Physical exercise and a low calorie diet in combination with the gradual loss of body weight represent the cornerstone for the management of NAFLD patients.

Interobserver and intraobserver variability in the sonographic assessment of fatty liver

OBJECTIVE

The purpose of this study was to evaluate interobserver and intraobserver variability in the sonographic assessment of the presence and severity of fatty liver.

MATERIALS AND METHODS

We retrospectively evaluated the static images of 168 adult patients who had undergone abdominal sonography. Three experienced radiologists independently graded the hepatic images as normal, mild steatosis, moderate steatosis, or severe steatosis. Assessment of liver steatosis was repeated on the same set of images 1 month later under the same conditions and blinded to the initial reading. Weighted kappa statistics were used to analyze interobserver and intraobserver agreement, and the agreement percentages were calculated.

RESULTS

The mean interobserver and intraobserver agreement rates for the presence of fatty liver were 72% (kappa = 0.43) and 76% (kappa = 0.54). For severity of fatty liver, the initial reading for pairs of observers had 47-59% (kappa = 0.40-0.51) interobserver agreement. The interobserver agreement for the second reading was 59-64% (kappa = 0.43-0.54). The mean agreement rates for pairs of observers were 53% (kappa = 0.47) and 62% (kappa = 0.50) on the first and second readings. Intraobserver agreement for severity of fatty liver ranged from 55% to 68% (kappa = 0.51-0.63).

CONCLUSION

Subjective visual assessment of fatty liver on sonography has substantial observer variability. There is a need for a more objective quantitative method of grading fatty liver on sonography that would be easily available and applicable in routine clinical practice.

Preoperative radiographic assessment of hepatic steatosis with histologic correlation

BACKGROUND

The adverse impact of hepatic steatosis on perioperative outcomes after liver resection is gaining recognition. But the accuracy of preoperative radiologic assessment of fatty liver disease remains unclear. The objective of this study was to correlate preoperative radiologic estimation with postoperative histologic measurement of steatosis.

STUDY DESIGN

Patients who underwent partial hepatectomy between 1997 and 2001, with complete preoperative radiographic imaging and postoperative pathologic assessment of steatosis, were retrospectively analyzed. The presence of steatosis was assessed radiographically using noncontrast-enhanced CT (NCCT), contrast-enhanced CT (CCT), or MRI, using standard quantitative radiologic criteria. Repeat histologic analysis was used to quantify the extent of hepatic steatosis.

RESULTS

One hundred thirty-one patients were studied. The overall sensitivity and specificity for all imaging modalities in detecting pathologically confirmed hepatic steatosis were 56% and 82%, respectively. Sensitivity and specificity for NCCT, CCT, and MRI using standard quantitative criteria were 33% and 100%, 50% and 83%, and 88%, and 63%, respectively. Increasing body mass indices adversely affected the accuracy of NCCT (p=0.002). Preoperative chemotherapy did not notably affect radiologic accuracy.

CONCLUSIONS

The presence of a fatty-appearing liver on NCCT scans indicates clinically significant steatosis, but steatosis cannot be excluded based on a normal NCCT scan, particularly in obese patients. Conversely, normal MRI helps to exclude hepatic steatosis, but abnormal MRI is not a reliable indicator of fatty change. CCT is not an effective means of identifying steatosis. We conclude that, when used alone, conventional cross-sectional imaging does not consistently permit accurate identification of hepatic steatosis.

Evaluation and management of obesity-related nonalcoholic fatty liver disease

The clinicopathologic spectrum of nonalcoholic fatty liver disease (NAFLD) ranges from simple steatosis to nonalcoholic steatohepatitis (NASH). Simple steatosis has a relatively benign clinical course, but NASH can progress to cirrhosis and hepatocellular carcinoma. NAFLD occurs in the absence of significant alcohol use and is considered to be the hepatic manifestation of metabolic syndrome. NAFLD affects approximately 30% of the US population and the incidence seems to be rising as the obesity epidemic continues. At present, the most accurate modality for the diagnosis of NASH is liver biopsy; however, many patients do not have a liver biopsy, and in the absence of more-accurate imaging technologies and serum markers, the diagnosis is frequently one of exclusion. As yet there is no convincingly effective treatment for NAFLD--a multimodal treatment plan that targets obesity, insulin resistance, hyperlipidemia and hypertension might be the best option for these patients.

Nonalcoholic fatty liver disease: from pathogenesis to patient care

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in Western countries. It encompasses a wide spectrum of liver lesions, from pure steatosis to end-stage liver disease with cirrhosis and hepatocellular carcinoma. Nonalcoholic steatohepatitis corresponds only to one stage of NAFLD. As NAFLD can be considered a liver manifestation of the metabolic syndrome, its prevalence is high in obese people and in patients who have type 2 diabetes-insulin resistance is one of the key elements of the pathogenesis of NAFLD. This disease is often asymptomatic in the absence of decompensated cirrhosis, but should be suspected in patients with elevated aminotransferase levels or radiological evidence of a fatty liver or hepatomegaly. Liver fibrosis is associated with age over 50 years, obesity, diabetes and high triglyceride levels. Liver biopsy is the only way to assess the histologic features of necrotic inflammation and fibrosis that define nonalcoholic steatohepatitis and to determine its probable prognosis. The prognosis is good for pure steatosis, whereas the presence of necrotic inflammation is associated with a significant risk of progression to cirrhosis and, possibly, hepatocellular carcinoma. Lifestyle changes, such as dietary modifications and exercise, are recommended. To date, there have been very few randomized, placebo-controlled trials of drug treatments for NAFLD.

MRI and ultrasound for hepatic fat quantification:relationships to clinical and metabolic characteristics of pediatric nonalcoholic fatty liver disease

OBJECTIVE

The aims of this study were to evaluate hepatic steatosis severity in a series of obese children through both magnetic resonance imaging (MRI) and ultrasound, and to correlate imaging findings to clinical and metabolic characteristics of the study population.

METHODS

Fifty obese children presenting hepatomegaly and/or elevated aminotransferases were candidates for assessment of hepatic fat fraction (HFF) by MRI. All subjects underwent dual energy X-ray absorptiometry scan measurement, and liver ultrasound scanning. Fasting blood samples were taken for the estimation of serum concentrations of glucose, insulin, leptin, aminotransferases and serum lipid profile.

RESULTS

A diagnosis of fatty liver was established by MRI in 20 (40%) children; of these, 12 had HFF of 9-18%, while the remaining ones had HFF of 19% or higher. HFF was not correlated to age, SDS-BMI, pubertal status and fat mass. HFF was positively associated with serum concentrations of alanine aminotransferase (ALT; r=0.62; p<0.0001) and AST (r=0.39; p=0.006), as well as with insulin (r=0.44; p=0.001) and insulin resistance (r=0.49; p<0.0001). Overall, ultrasound correlated well with MRI (p<0.0001). However, HFF ranged greatly in subjects with moderate (2-37%) as well as with severe (11-25%) degree of ultrasound hepatic steatosis. In fact, the mean hepatic fat fraction in children with severe steatosis was not statistically different from that found in patients with moderate steatosis (p=0.98). In multiple regression analysis, the most powerful predictors of elevated ALT, after correction for age, gender, BMI and pubertal status, were insulin resistance (p<0.01) and MRI HFF (p<0.0001).

CONCLUSIONS

Unlike sonography, an operator-dependent procedure, MRI is not subject to interpretation or inter-observer variation, and may be more useful than ultrasound for the monitoring of young patients with hepatic steatosis.

Noninvasive assessment of fibrosis in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH)

The term "non-alcoholic fatty liver disease" (NAFLD) encompasses a wide range of pathological conditions ranging from accumulation of fat (fatty liver) to various degrees of inflammation and fibrosis (NASH), and finally to cryptogenic cirrhosis and its clinical sequelae (HCC, liver decompensation). The progression from one stage to the next can be triggered by genetic and environmental factors alone and also through their interaction. Fatty liver is known to follow a benign course, whereas the presence of inflammation, ballooning degeneration, and fibrosis, which are typical features of NASH, can lead to cirrhosis. Despite the serious risks associated with NASH, there are few tools for monitoring the progression of the disease and identification of high-risk patients. The aim of this article is to review the pros and cons of some noninvasive methods for assessing liver fibrosis in NASH.

Relationship among histologic, radiologic, and biochemical assessments of hepatic steatosis: a study of human liver samples

BACKGROUND AND AIMS

In patients with nonalcoholic fatty liver disease, there is not a consistent relationship between severity of steatosis and the presence of steatohepatitis. This leads to the possibility that severity of steatosis is not an important factor in the pathogenesis of nonalcoholic steatohepatitis. Alternatively, it is possible that currently used method to quantify hepatic steatosis (histologic grading) may not accurately reflect hepatic lipid content. Therefore, we examined the relationship between hepatic triglyceride (TG) content and nonbiochemical assessment of steatosis in 38 human liver samples.

METHODS

Hepatic steatosis was histologically graded by the 3 hepatopathologists and hepatic TG levels were determined from liver homogenate. Additionally, we characterized the relationship between (a) hepatic steatosis quantified by magnetic resonance spectroscopy (MRS) and histologic grading and hepatic TG content and (b) hepatic long-chain polyunsaturated fatty acid n-6/n-3 ratio and the severity of steatosis.

RESULTS

Twenty-two samples had <5% steatosis, 9 had 5% to 33% steatosis and 7 had >33% steatosis. The mean (+/-SD) hepatic TG was 1.8+/-1.3 mg/mg of protein and MRS fat score was 6.4+/-6.0. There was a significant correlation between histologic grading and hepatic TG content (r=0.64, P<0.001). A significant correlation existed between MRS fat score and histologic grading (r=0.61, P=0.006), and hepatic TG (r=0.63, P=0.004). Severity of steatosis as graded histologically had significant correlation with n-6/n-3 ratio (r=0.61, P<0.001).

CONCLUSIONS

Hepatic steatosis quantified by histologic grading or by MRS is significantly reflective of hepatic TG content. Further research is needed to investigate the relationship we observed between n-6/n-3 ratio and the severity of steatosis.

Ultrasonographic evaluation of liver volume and the metabolic syndrome in obese women

Non-alcoholic fatty liver disease is a common finding in obese subjects, and increasing evidence has been provided suggesting that it represents the hepatic component of the metabolic syndrome. The aim of this study was to evaluate whether the extent of liver enlargement is related to the severity of the metabolic syndrome in obese women. The relationship between ultrasound- measured hepatic left lobe volume (HLLV) and various features of the metabolic syndrome was evaluated in 85 obese women. The mean+/-SD value of HLLV in obese women was 431+/-214 ml (range 46-1019 ml) while it was 187+/-31 ml (range 143-258 ml) in lean subjects. In a multiple logistic regression analysis, ultrasound-measured intra-abdominal fat was the only anthropometric measure independently associated with HLLV. A strong positive association was found between HLLV and serum liver enzymes, triglycerides, glucose, insulin, uric acid, C reactive protein, systolic and diastolic blood pressure, while a negative correlation was observed between HLLV and HDL cholesterol. The values of HLLV corresponding to the cut-off values of various risk factors for the diagnosis of the metabolic syndrome were calculated, yielding a mean value of 465 ml. In conclusion, ultrasound measurement of HLLV represents a simple, reliable and low-cost tool for the evaluation of liver involvement in the metabolic syndrome. The strong association between liver enlargement and various cardiovascular risk factors associated with insulin resistance supports the role of liver steatosis as an important link among the many facets of the metabolic syndrome in human obesity.

Role of radiologic modalities in the management of non-alcoholic steatohepatitis

During the last decade, the role of radiologic modalities in management of patients who have fatty liver disease has expanded. Ultrasonography has been used as a noninvasive alternative to biopsy for monitoring patients who have hepatic steatosis, but MRI is more appealing than ultrasonography to denote minor changes in hepatic fat content. Distinguishing patients who have non-alcoholic steatohepatitis from steatosis alone has become of clinical importance; however, the differences are not apparent with any radiologic modalities. Several modalities have been developed to noninvasively and accurately quantify hepatic fat content and diagnose steatohepatitis. In the future, radiologic modalities might be used to monitor the natural history of the disease or evaluate therapeutic interventions in patients who have non-alcoholic fatty liver disease.

Inhibition of microsomal triglyceride transfer protein in familial hypercholesterolemia

BACKGROUND

Patients with homozygous familial hypercholesterolemia have markedly elevated cholesterol levels, which respond poorly to drug therapy, and a very high risk of premature cardiovascular disease. Inhibition of the microsomal triglyceride transfer protein may be effective in reducing cholesterol levels in these patients.

METHODS

We conducted a dose-escalation study to examine the safety, tolerability, and effects on lipid levels of BMS-201038, an inhibitor of the microsomal triglyceride transfer protein, in six patients with homozygous familial hypercholesterolemia. All lipid-lowering therapies were suspended 4 weeks before treatment. The patients received BMS-201038 at four different doses (0.03, 0.1, 0.3, and 1.0 mg per kilogram of body weight per day), each for 4 weeks, and returned for a final visit after a 4-week drug washout period. Analysis of lipid levels, safety laboratory analyses, and magnetic resonance imaging of the liver for fat content were performed throughout the study.

RESULTS

All patients tolerated titration to the highest dose, 1.0 mg per kilogram per day. Treatment at this dose decreased low-density lipoprotein (LDL) cholesterol levels by 50.9% and apolipoprotein B levels by 55.6% from baseline (P<0.001 for both comparisons). Kinetic studies showed a marked reduction in the production of apolipoprotein B. The most serious adverse events were elevation of liver aminotransferase levels and accumulation of hepatic fat, which at the highest dose ranged from less than 10% to more than 40%.

CONCLUSIONS

Inhibition of the microsomal triglyceride transfer protein by BMS-201038 resulted in the reduction of LDL cholesterol levels in patients with homozygous familial hypercholesterolemia, owing to reduced production of apolipoprotein B. However, the therapy was associated with elevated liver aminotransferase levels and hepatic fat accumulation.

Fatty liver is an integral feature of familial combined hyperlipidaemia: relationship with fat distribution and plasma lipids

Overproduction of VLDL (very-low-density lipoprotein) particles is an important cause of FCHL (familial combined hyperlipidaemia). It has been shown recently that VLDL production is driven by the amount of hepatic fat. The present study was conducted to determine the prevalence of fatty liver in relation to the different fat compartments and lipid parameters in FCHL. A total of 68 FCHL patients, 110 normolipidaemic relatives and 66 spouses underwent ultrasound of the abdominal region to estimate the amount of subcutaneous, visceral and hepatic fat. Skinfold callipers were used to measure subcutaneous fat of the biceps, triceps, subscapular and supra-iliacal regions. Fatty liver was observed in 18% of the spouses, 25% of the normolipidaemic relatives and 49% of the FCHL patients. After adjustment for age, gender and body mass index, the prevalence of fatty liver was significantly higher in FCHL patients compared with spouses [OR (odds ratio), 3.1; P=0.03], and also in the normolipidaemic relatives compared with spouses (OR, 4.0; P=0.02), whereas no differences were observed between FCHL patients and normolipidaemic relatives (OR, 0.8; P=0.58). In the normolipidaemic relatives and FCHL patients combined, both visceral fat mass and subcutaneous abdominal fat were independent predictors of fatty liver (P<0.001 for both fat compartments; FCHL status corrected). Of interest, fatty liver stages were correlated with both VLDL-apoB (apolipoprotein B) and VLDL-triacylglycerols (triglycerides) in a representative subset (n=69) of patients and relatives (r2=0.12, P=0.006; and r2=0.18, P=0.001 respectively). These results show that fatty liver is a central aspect of FCHL, i.e. patients and normolipidaemic relatives. Both visceral and subcutaneous adiposity contribute to its 3–4-fold higher risk in FCHL.

Imaging of hepatic steatosis and fatty sparing

Radiology has gained importance in the non-invasive diagnosis of hepatic steatosis. Ultrasonography is usually the first imaging modality for the evaluation of hepatic steatosis. Unenhanced CT with or without dual kVp measurement and MRI with in and out of phase sequence can allow objective evaluation of hepatic steatosis. However, none of the imaging modalities can differentiate non-alcoholic steatohepatitis/fatty liver disease from simple steatosis. Evaluation of hepatic steatosis is important in donor evaluation before orthotopic liver transplantation and hepatic surgery. Recently, one-stop shop evaluation of potential liver donors has become possible by CT and MRI integrating vascular, parenchymal, volume and steatosis evaluation. Moreover hepatic steatosis (diffuse, multinodular, focal, subcortical, perilesional, intralesional, periportal and perivenular), hypersteatosis and sparing (geographic, nodular and perilesional or peritumoral) can cause diagnostic problems as a pseudotumor particularly in the evaluation of oncology patients. Liver MRI is used as a problem-solving tool in these patients. In this review, we discuss the current role of radiology in diagnosing, quantifying hepatic steatosis and solutions for diagnostic problems associated with fatty infiltration and sparing.

Pediatric nonalcoholic fatty liver disease: a critical appraisal of current data and implications for future research

Although population prevalence is very difficult to establish, nonalcoholic fatty liver disease (NAFLD) is probably the most common cause of liver disease in the preadolescent and adolescent age groups. There seems to be an increase in the prevalence of NAFLD, likely related to the dramatic rise in the incidence of obesity during the past 3 decades. Despite an increase in public awareness, overweight/obesity and related conditions, such as NAFLD, remain underdiagnosed by health care providers. Accurate diagnosis and staging of nonalcoholic steatohepatitis (NASH) requires liver biopsy. The development of noninvasive surrogate markers and the advancements in imaging technology will aid in the screening of large populations at risk for NAFLD. Two distinct histological patterns of NASH have been identified in the pediatric population, and discrete clinical and demographic features are observed in children with these 2 patterns. The propensity for NASH to develop in obese, insulin-resistant pubertal boys of Hispanic ethnicity or a non-Hispanic white race may provide clues to the pathogenesis of NAFLD in children. The natural history of pediatric NASH has yet to be defined, but most biopsies in this age group demonstrate some degree of fibrosis. In addition, cirrhosis can be observed in children as young as 10 years. While the optimal treatment of pediatric NAFLD has yet to be determined, lifestyle modification through diet and exercise should be attempted in children diagnosed with NAFLD. A large, multicenter trial of vitamin E and metformin is underway as part of the NASH clinical research network.

Heritability and genetic loci of fatty liver in familial combined hyperlipidemia

VLDL overproduction, a process that is driven by an excess amount of hepatic fat, is a well-documented feature of familial combined hyperlipidemia (FCHL). The aims of this study were to investigate whether fatty liver, measured with ultrasound and as plasma alanine aminotransferase (ALT) levels, develops against a genetic background in FCHL and to identify chromosomal loci that are linked to these traits. In total, 157 FCHL family members and 20 spouses participated in this study. Radiological evidence of fatty liver was more prevalent not only in FCHL probands (40%) but also in their relatives (35%) compared with spouses (15%) (P < 0.05). Heritability calculations revealed that 20-36% of the variability in ALT levels could be attributed to genetic factors. Nonparametric quantitative trait locus (QTL) analysis revealed three significant (P < 0.001) loci with either the ultrasound or the ALT trait in the male sample: 1q42.3, 7p12-21, and 22p13-q11; none was found in the female sample or the entire group. Of these QTLs, the 7p region was consistent over time, because reanalysis with ALT levels that were determined during a visit 5 years earlier yielded similar results. This study shows that fatty liver is a heritable aspect of FCHL. Replication of particularly the 7p region is awaited.

Drug-induced liver injury: summary of a single topic clinical research conference

Idiosyncratic drug induced liver injury (DILI) remains poorly understood. It is assumed that the affected individuals possess a rare combination of genetic and non genetic factors that, if identified, would greatly improve understanding of the underlying mechanisms. This single topic conference brought together basic scientists, translational investigators, and clinicians with an interest in DILI. The goal was to define high priority areas of investigation that will soon be made possible by The Drug-Induced Liver Injury Network (DILIN). Since 2004 DILIN has been collecting clinical data, genomic DNA and some tissues from patients who have experienced bone fide DILI. The presentations spanned many different areas of DILI, and included novel data concerning mechanisms of hepatotoxicity, new "omics" approaches, and the challenges of improving causation assessment.

Nonalcoholic fatty liver disease: from steatosis to cirrhosis

Nonalcoholic steatohepatitis (NASH), the lynchpin between steatosis and cirrhosis in the spectrum of nonalcoholic fatty liver disorders (NAFLD), was barely recognized in 1981. NAFLD is now present in 17% to 33% of Americans, has a worldwide distribution, and parallels the frequency of central adiposity, obesity, insulin resistance, metabolic syndrome and type 2 diabetes. NASH could be present in one third of NAFLD cases. Age, activity of steatohepatitis, and established fibrosis predispose to cirrhosis, which has a 7- to 10-year liver-related mortality of 12% to 25%. Many cases of cryptogenic cirrhosis are likely endstage NASH. While endstage NAFLD currently accounts for 4% to 10% of liver transplants, this may soon rise. Pathogenic concepts for NAFLD/NASH must account for the strong links with overnutrition and underactivity, insulin resistance, and genetic factors. Lipotoxicity, oxidative stress, cytokines, and other proinflammatory mediators may each play a role in transition of steatosis to NASH. The present "gold standard" management of NASH is modest weight reduction, particularly correction of central obesity achieved by combining dietary measures with increased physical activity. Whether achieved by "lifestyle adjustment" or anti-obesity surgery, this improves insulin resistance and reverses steatosis, hepatocellular injury, inflammation, and fibrosis. The same potential for "unwinding" fibrotic NASH is indicated by studies of the peroxisome proliferation activator receptor (PPAR)-gamma agonist "glitazones," but these agents may improve liver disease at the expense of worsening obesity. Future challenges are to approach NAFLD as a preventive public health initiative and to motivate affected persons to adopt a healthier lifestyle.