The existing systems for scoring fibrosis were not developed to evaluate transplanted livers. Our aim was to design and validate a novel fibrosis scoring system specifically adapted to assess liver allograft fibrosis (LAF). Clinical data, histology, transient elastography (TE) and AST/platelet ratio index (APRI) were reviewed in 38 pediatric liver transplant (LT) recipients. Protocol liver biopsies performed at 6 months and 7 years post-LT were reviewed by three pathologists who assessed LAF using the METAVIR and Ishak systems. LAF was also scored separately in portal (0-3), sinusoidal (0-3) and centrolobular areas (0-3). Scoring evaluations were correlated with fibrosis quantification using morphometry, and also with TE and APRI. Statistical correlations between morphometry and METAVIR were 0.571 (p < 0.000) and 0.566 (p < 0.000) for the Ishak system. The novel score (0-9) for separate assessment of portal, sinusoidal and centrolobular fibrosis showed a better correlation with morphometry (0.731; p < 0.000) and high intra-/interobserver agreement (0.966; p < 0.000 and 0.794; p < 0.000, respectively). No correlation was found between TE or APRI and morphometry or the three histologic scores. In conclusion, this novel semiquantitative fibrosis scoring system seems to more accurately reflect LAF than the existing scoring system and may become a practical tool for staging fibrosis in LT.
Purpose: To assess whether hepatic fibrosis is associated with a restriction in the diffusion of water that can be analyzed with diffusion-weighted MR imaging (DWI) of the liver.
Materials and Methods:DWI was performed in 10 normal rats and 15 rats with liver fibrosis. Echo-planar DWI was performed in the living rats at 1.5 T and repeated immediately after the animals were killed. Afterwards the livers were explanted, fixed in Bouin solution, and imaged with a DW spin-echo sequence at 4.7 T. Fibrosis was quantified by densitometry on Sirius red-stained histological sections.
Results:In living rats the apparent diffusion coefficient (ADC) decreased with the severity of liver fibrosis (controls: 1535 Ϯ 294 mm 2 /second; CCl 4 (5 weeks) 1129 Ϯ 273 mm 2 /second; CCl 4 (9 weeks): 943 Ϯ 132 mm 2 /second; P ϭ 0.002). An inverse correlation between ADC and liver fibrosis volume density was observed (r ϭ -0.712, P Ͻ 0.001). In contrast, these findings were not observed in the rats after they were killed or in the fixated livers.
Conclusion:Decreased ADC correlated with increased liver fibrosis in living rats, but not after death. These results suggest that restricted water diffusion cannot be assessed by DWI in liver fibrosis. Other factors, such as a decrease of perfusion, may explain the decrease of the hepatic ADC measured in vivo in rats with liver fibrosis.
Purpose: To determine the correlations between the viscoelastic parameters of the liver measured with in vivo MR elastography and quantitative analysis of liver fibrosis.
Materials and Methods:MR elastography of the liver was performed in 10 rats with hepatic fibrosis induced by intraperitoneal carbon tetrachloride (CCl 4 ) injections and five normal rats. Longitudinal waves of 200 MHz were transmitted into the liver with a mechanical transducer. Wave propagation into the liver was analyzed with a phase-locked spin-echo sequence at 1.5 T. The viscoelastic parameters, obtained with the Voigt model, were correlated with automatic image analysis of the fibrotic areas and with analysis of the hydroxyproline content of the liver.Results: Substantial correlations were observed between the shear viscoelastic parameters and the percentage of fibrosis at automatic image analysis (r ϭ 0.7, P ϭ 0.005 for the elasticity, and r ϭ 0.8, P ϭ 0.001 for the viscosity) and moderate correlations were seen between the shear viscoelastic parameters and the hydroxyproline content (r ϭ 0.6, P ϭ 0.016 for the elasticity and r ϭ 0.5, P ϭ 0.041 for the viscosity).
Conclusion:The viscoelastic parameters of the liver measured with in vivo MR elastography correlate with quantitative analysis of liver fibrosis. These results suggest that MR elastography is a promising noninvasive method to quantify liver fibrosis.
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