Texture-based classification of liver fibrosis using MRI.

PURPOSE: To investigate the ability of texture analysis of MRI images to stage liver fibrosis. Current noninvasive approaches for detecting liver fibrosis have limitations and cannot yet routinely replace biopsy for diagnosing significant fibrosis. MATERIALS AND METHODS: Forty-nine patients with a range of liver diseases and biopsy-confirmed fibrosis were enrolled in the study. For texture analysis all patients were scanned with a T2 -weighted, high-resolution, spin echo sequence and Haralick texture features applied. The area under the receiver operating characteristics curve (AUROC) was used to assess the diagnostic performance of the texture analysis. RESULTS: The best mean AUROC achieved for separating mild from severe fibrosis was 0.81. The inclusion of age, liver fat and liver R2 variables into the generalized linear model improved AUROC values for all comparisons, with the F0 versus F1-4 comparison the highest (0.91). CONCLUSION: Our results suggest that a combination of MRI measures, that include selected texture features from T2 -weighted images, may be a useful tool for excluding fibrosis in patients with liver disease. However, texture analysis of MRI performs only modestly when applied to the classification of patients in the mild and intermediate fibrosis stages.

Analysis of the intrahepatic ductular reaction and progenitor cell responses in hepatitis C virus recurrence after liver transplantation.

Fibrosis in livers with hepatitis C virus (HCV) recurrence after liver transplantation (LT) can be rapidly progressive, and the mechanisms underlying this process are poorly understood. In livers with HCV infections in the non-LT setting, there is a significant relationship between the development of structures known as the ductular reaction (DR), hepatic progenitor cells (HPCs), and fibrosis. This study characterizes the DR, HPCs, and fibrosis associated with HCV recurrence after LT. Immunohistochemistry and confocal microscopy were used to characterize the DR, HPC, and fibrosis in liver biopsy specimens. Key findings were confirmed in a separate, independent cohort. The initial characterization cohort had 194 biopsy samples from 105 individuals with HCV recurrence after LT. The immunophenotype, morphology, and location of the DR were consistent with an HPC origin. The DR correlated with intrahepatic fibrosis (rs = 0.529, P < 0.001) and the number of activated hepatic stellate cells (HSCs; rs = 0.446, P < 0.001). There was an early occurrence of hepatocyte replicative arrest as well as increased hepatocyte proliferation that correlated with the DR (rs = 0.295, P < 0.001). Replicative arrest preceded hepatocyte proliferation in early-stage injury. Hepatocyte proliferation decreased with advanced fibrosis; in contrast, the extent of the DR and the number of activated HSCs continued to increase. In the second cohort of 37 individuals, the DR and the number of HPCs similarly correlated with fibrosis and inflammation after LT. In conclusion, this is the first characterization of the DR in HCV-associated liver injury after LT. There was a significant correlation between the DR and the development of progressive fibrosis in HCV recurrence. These results suggest a pivotal role for both the DR and the HPC responses in the aggressive fibrosis seen with HCV recurrence after LT.

Disruption of hemochromatosis protein and transferrin receptor 2 causes iron-induced liver injury in mice.

UNLABELLED: Mutations in hemochromatosis protein (HFE) or transferrin receptor 2 (TFR2) cause hereditary hemochromatosis (HH) by impeding production of the liver iron-regulatory hormone, hepcidin (HAMP). This study examined the effects of disruption of Hfe or Tfr2, either alone or together, on liver iron loading and injury in mouse models of HH. Iron status was determined in Hfe knockout (Hfe(-/-)), Tfr2 Y245X mutant (Tfr2(mut)), and double-mutant (Hfe(-/-) ×Tfr2(mut) ) mice by measuring plasma and liver iron levels. Plasma alanine transaminase (ALT) activity, liver histology, and collagen deposition were evaluated to assess liver injury. Hepatic oxidative stress was assessed by measuring superoxide dismutase (SOD) activity and F(2)-isoprostane levels. Gene expression was measured by real-time polymerase chain reaction. Hfe(-/-) ×Tfr2(mut) mice had elevated hepatic iron with a periportal distribution and increased plasma iron, transferrin saturation, and non-transferrin-bound iron, compared with Hfe(-/-), Tfr2(mut), and wild-type (WT) mice. Hamp1 expression was reduced to 40% (Hfe(-/-) and Tfr2(mut) ) and 1% (Hfe(-/-) ×Tfr2(mut)) of WT values. Hfe(-/-) ×Tfr2(mut) mice had elevated plasma ALT activity and mild hepatic inflammation with scattered aggregates of infiltrating inflammatory cluster of differentiation 45 (CD45)-positive cells. Increased hepatic hydoxyproline levels as well as Sirius red and Masson's Trichrome staining demonstrated advanced portal collagen deposition. Hfe(-/-) and Tfr2(mut) mice had less hepatic inflammation and collagen deposition. Liver F(2) -isoprostane levels were elevated, and copper/zinc and manganese SOD activities decreased in Hfe(-/-) ×Tfr2(mut), Tfr2(mut), and Hfe(-/-) mice, compared with WT mice. CONCLUSION: Disruption of both Hfe and Tfr2 caused more severe hepatic iron overload with more advanced lipid peroxidation, inflammation, and portal fibrosis than was observed with the disruption of either gene alone. The Hfe(-/-) ×Tfr2(mut) mouse model of iron-induced liver injury reflects the liver injury phenotype observed in human HH.

Natural history and management of HFE-hemochromatosis.

Advances in our knowledge of hereditary hemochromatosis (HH) over the past 150 years have revealed new insights into this common genetic disorder. Meticulous family and HLA association studies followed ultimately by cloning of the HFE gene have dramatically changed our understanding of the natural history and manifestations of HH. Cross-sectional studies demonstrated that HH had a highly variable clinical and biochemical penetrance in susceptible individuals of northern European descent. "State-of-the-art" large longitudinal population studies have accurately defined the natural history. We now recognize that HH is not as discreet an entity as previously thought because genetic and environmental modifiers of disease penetrance are increasingly identified as influencing the clinical course of HH. While phlebotomy remains the cornerstone of therapy, our diagnostic approach has been refined to incorporate new biochemical, genetic, and noninvasive methods that complement more traditional approaches. This review aims to encapsulate this new knowledge in a framework that addresses commonly raised issues relating to the current natural history, diagnosis, and management of HH patients.

Phenotypic expression of hereditary hemochromatosis: what have we learned from the population studies?

Profound advances in our knowledge of hereditary hemochromatosis (HH) during the past 150 years have resulted in two distinct "iron ages": the pre-HFE gene era and the post-HFE gene era. During these periods, family studies, HLA association studies, and ultimately HFE gene studies in various populations informed us of the genotypic prevalence as well as the clinical and biochemical penetrance of HH. We learned that HH has a highly variable clinical penetrance in susceptible individuals of Northern European ancestry. Further, we now recognize that the natural history of HH is not as discrete as previously believed, because genetic and environmental modifiers of disease penetrance are increasingly identified as influencing the clinical expression of HH.

Stereological Analysis of Liver Biopsy Histology Sections as a Reference Standard for Validating Non-Invasive Liver Fat Fraction Measurements by MRI.

BACKGROUND AND AIMS: Validation of non-invasive methods of liver fat quantification requires a reference standard. However, using standard histopathology assessment of liver biopsies is problematical because of poor repeatability. We aimed to assess a stereological method of measuring volumetric liver fat fraction (VLFF) in liver biopsies and to use the method to validate a magnetic resonance imaging method for measurement of VLFF. METHODS: VLFFs were measured in 59 subjects (1) by three independent analysts using a stereological point counting technique combined with the Delesse principle on liver biopsy histological sections and (2) by three independent analysts using the HepaFat-Scan® technique on magnetic resonance images of the liver. Bland Altman statistics and intraclass correlation (IC) were used to assess the repeatability of each method and the bias between the methods of liver fat fraction measurement. RESULTS: Inter-analyst repeatability coefficients for the stereology and HepaFat-Scan® methods were 8.2 (95% CI 7.7-8.8)% and 2.4 (95% CI 2.2-2.5)% VLFF respectively. IC coefficients were 0.86 (95% CI 0.69-0.93) and 0.990 (95% CI 0.985-0.994) respectively. Small biases (≤3.4%) were observable between two pairs of analysts using stereology while no significant biases were observable between any of the three pairs of analysts using HepaFat-Scan®. A bias of 1.4±0.5% VLFF was observed between the HepaFat-Scan® method and the stereological method. CONCLUSIONS: Repeatability of the stereological method is superior to the previously reported performance of assessment of hepatic steatosis by histopathologists and is a suitable reference standard for validating non-invasive methods of measurement of VLFF.

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.

Screening for hereditary haemochromatosis.

Hereditary haemochromatosis (HH) is a common autosomal recessive disorder of iron overload in Caucasian populations. Clinical manifestations usually occur in individuals homozygous for the C282Y mutation in the HFE gene product and who have developed significant iron loading. Current screening methods can detect affected individuals either prior to or early during disease evolution, enabling early introduction of phlebotomy treatment that can normalise life expectancy. Evaluation of possible iron overload, via measurement of serum transferrin saturation and ferritin level, is the most appropriate initial test for those subjects presenting clinically for evaluation. HFE genotyping, when combined with serum biochemical measurements, defines the presence of likely iron overload and the underlying genetic disorder and is the preferred initial screening modality for families of an affected individual. Definitive proof of iron overload requires measurement of hepatic iron concentration or total iron burden via therapeutic phlebotomy; elevated serum ferritin level alone is not adequate. We now recognise that the natural history of HH is not as discrete as previously believed, because genetic and environmental modifiers of disease penetrance are increasingly identified as influencing the clinical expression of HH. In fact, a minority of C282Y homozygotes develop classical 'iron overload disease', although it has recently emerged that the disorder may predispose to breast and colorectal cancer. Uncertainties as to the true clinical impact of the condition at a population level lead to current recommendations of cascade screening of families of affected patients, case-finding in high-risk groups, such as patients with clinical manifestations consistent with the diagnosis, and a high level of clinical awareness in the community to facilitate early diagnosis. Generalised population screening is not presently recommended.

Genetics of hereditary hemochromatosis: a clinical perspective.

Hereditary hemochromatosis due to homozygosity for the C282Y mutation in the HFE gene product is the most common autosomal recessive genetic disorder in populations of northern European descent, where it attains a maximum prevalence of approximately one in 200. Cross-sectional and longitudinal studies have revealed that clinically significant iron-overload disease develops in at least 28% of male and 1% of female HFE C282Y homozygotes. The relatively low clinical penetrance is largely unexplained. Current evidence suggests a limited role for digenic inheritance of mutations in iron homeostasis genes in modifying the penetrance of hemochromatosis. Male gender is a strong genetic factor, promoting expression of clinical disease. Dietary intake of alcohol and noncitrus fruit may also act as important environmental modifiers of penetrance. With genetic analyses becoming simpler to perform, new genetic modifiers of hepatic iron loading and liver fibrogenesis are likely to be forthcoming.