Computer-assisted image analysis of liver collagen: relationship to Ishak scoring and hepatic venous pressure gradient

Liver fibrosis analysis using digital pathology

Digital pathology has enabled the noninvasive quantification of pathological parameters. In addition, the combination of digital pathology and artificial intelligence has enabled the analysis of a vast amount of information, leading to the sharing of much information and the elimination of knowledge gaps. Fibrosis, which reflects chronic inflammation, is the most important pathological parameter in chronic liver diseases, such as viral hepatitis and metabolic dysfunction-associated steatotic liver disease. It has been reported that the quantitative evaluation of various fibrotic parameters by digital pathology can predict the prognosis of liver disease and hepatocarcinogenesis. Liver fibrosis evaluation methods include 1 fiber quantification, 2 elastin and collagen quantification, 3 s harmonic generation/two photon excitation fluorescence (SHG/TPE) microscopy, and 4 Fibronest™..　In this review, we provide an overview of role of digital pathology on the evaluation of fibrosis in liver disease and the characteristics of recent methods to assess liver fibrosis.

Obliteration of portal venules contributes to portal hypertension in biliary cirrhosis

The effects of the obliteration of portal venules (OPV) in cirrhotic portal hypertension are poorly understood. To investigate its contribution to portal hypertension in biliary cirrhosis and its underlying mechanism, we evaluated OPV using two-dimensional (2D) histopathology in liver explants from patients with biliary atresia (BA, n = 63), primary biliary cholangitis (PBC, n = 18), and hepatitis B-related cirrhosis (Hep-B-cirrhosis, n = 35). Then, three-dimensional (3D) OPV was measured by X-ray phase-contrast CT in two parallel models in rats following bile duct ligation (BDL) or carbon tetrachloride (CCl4) administration, representing biliary cirrhosis and post-necrotic cirrhosis, respectively. The portal pressure was also measured in the two models. Finally, the effects of proliferative bile ducts on OPV were investigated. We found that OPV was significantly more frequent in patients with biliary cirrhosis, including BA (78.57 ± 16.45%) and PBC (60.00 ± 17.15%), than that in Hep-B-cirrhotic patients (29.43 ± 14.94%, p < 0.001). OPV occurred earlier, evidenced by the paired liver biopsy at a Kasai procedure (KP), and was irreversible even after a successful KP in the patients with BA. OPV was also significantly more frequent in the BDL models than in the CCl4 models, as shown by 2D and 3D quantitative analysis. Portal pressure was significantly higher in the BDL model than that in the CCl4 model. With the proliferation of bile ducts, portal venules were compressed and irreversibly occluded, contributing to the earlier and higher portal pressure in biliary cirrhosis. OPV, as a pre-sinusoidal component, plays a key role in the pathogenesis of portal hypertension in biliary cirrhosis. The proliferated bile ducts and ductules gradually take up the 'territory' originally attributed to portal venules and compress the portal venules, which may lead to OPV in biliary cirrhosis. © 2024 The Pathological Society of Great Britain and Ireland.

A data-driven approach to decode metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD), defined by the presence of liver steatosis together with at least one out of five cardiometabolic factors, is the most common cause of chronic liver disease worldwide, affecting around one in three people. Yet the clinical presentation of MASLD and the risk of progression to cirrhosis and adverse clinical outcomes is highly variable. It, therefore, represents both a global public health threat and a precision medicine challenge. Artificial intelligence (AI) is being investigated in MASLD to develop reproducible, quantitative, and automated methods to enhance patient stratification and to discover new biomarkers and therapeutic targets in MASLD. This review details the different applications of AI and machine learning algorithms in MASLD, particularly in analyzing electronic health record, digital pathology, and imaging data. Additionally, it also describes how specific MASLD consortia are leveraging multimodal data sources to spark research breakthroughs in the field. Using a new national-level 'data commons' (SteatoSITE) as an exemplar, the opportunities, as well as the technical challenges of large-scale databases in MASLD research, are highlighted.

Liver fibrosis phenotyping and severity scoring by quantitative image analysis of biopsy slides

BACKGROUND & AIMS

Digital pathology image analysis can phenotype liver fibrosis using histological traits that reflect collagen content, morphometry and architecture. Here, we aimed to calculate fibrosis severity scores to quantify these traits.

METHODS

Liver biopsy slides were categorised by Ishak stage and aetiology. We used a digital pathology technique to calculate four fibrosis severity scores: Architecture Composite Score (ACS), Collagen Composite Score (CCS), Morphometric Composite Score (MCS) and Phenotypic Fibrosis Composite Score (PH-FCS). We compared how these scores varied according to disease stage and aetiology.

RESULTS

We included 80 patients (40% female, mean age 59.0 years, mean collagen proportionate area 17.1%) with mild (F0-2, n = 28), moderate (F3-4, n = 17) or severe (F5-6, n = 35) fibrosis. All four aetiology independent scores corelated with collagen proportionate area (ACS: rp  = .512, CCS: rp  = .727, MCS: rp  = .777, PFCS: r = .772, p < .01 for all) with significant differences between moderate and severe fibrosis (p < .05). ACS increased primarily between moderate and severe fibrosis (by 95% to 226% depending on underlying aetiology), whereas MCS and CCS accumulation was more varied. We used 28 qFTs that distinguished between autoimmune- and alcohol-related liver disease to generate an MCS that significantly differed between mild and severe fibrosis for these aetiologies (p < .05).

CONCLUSIONS

We describe four aetiology-dependent and -independent severity scores that quantify fibrosis architecture, collagen content and fibre morphometry. This approach provides additional insight into how progression of architectural changes and accumulation of collagen may differ depending on underlying disease aetiology.

Digital pathology for nonalcoholic steatohepatitis assessment

Histological assessment of nonalcoholic fatty liver disease (NAFLD) has anchored knowledge development about the phenotypes of the condition, their natural history and their clinical course. This fact has led to the use of histological assessment as a reference standard for the evaluation of efficacy of drug interventions for nonalcoholic steatohepatitis (NASH) - the more histologically active form of NAFLD. However, certain limitations of conventional histological assessment systems pose challenges in drug development. These limitations have spurred intense scientific and commercial development of machine learning and digital approaches towards the assessment of liver histology in patients with NAFLD. This research field remains an area in rapid evolution. In this Perspective article, we summarize the current conventional assessment of NASH and its limitations, the use of specific digital approaches for histological assessment, and their application to the study of NASH and its response to therapy. Although this is not a comprehensive review, the leading tools currently used to assess therapeutic efficacy in drug development are specifically discussed. The potential translation of these approaches to support routine clinical assessment of NAFLD and an agenda for future research are also discussed.

Survey of liver pathologists to assess attitudes towards digital pathology and artificial intelligence

AIMS

A survey of members of the UK Liver Pathology Group (UKLPG) was conducted, comprising consultant histopathologists from across the UK who report liver specimens and participate in the UK National Liver Pathology External Quality Assurance scheme. The aim of this study was to understand attitudes and priorities of liver pathologists towards digital pathology and artificial intelligence (AI).

METHODS

The survey was distributed to all full consultant members of the UKLPG via email. This comprised 50 questions, with 48 multiple choice questions and 2 free-text questions at the end, covering a range of topics and concepts pertaining to the use of digital pathology and AI in liver disease.

RESULTS

Forty-two consultant histopathologists completed the survey, representing 36% of fully registered members of the UKLPG (42/116). Questions examining digital pathology showed respondents agreed with the utility of digital pathology for primary diagnosis 83% (34/41), second opinions 90% (37/41), research 85% (35/41) and training and education 95% (39/41). Fatty liver diseases were an area of demand for AI tools with 80% in agreement (33/41), followed by neoplastic liver diseases with 59% in agreement (24/41). Participants were concerned about AI development without pathologist involvement 73% (30/41), however, 63% (26/41) disagreed when asked whether AI would replace pathologists.

CONCLUSIONS

This study outlines current interest, priorities for research and concerns around digital pathology and AI for liver pathologists. The majority of UK liver pathologists are in favour of the application of digital pathology and AI in clinical practice, research and education.

Quantification of collagen fiber properties in alcoholic liver fibrosis using polarization-resolved second harmonic generation microscopy

Liver fibrosis is assessed mainly by conventional staining or second harmonic generation (SHG) microscopy, which can only provide collagen content in fibrotic area. We propose to use polarization-resolved SHG (PR-SHG) microscopy to quantify liver fibrosis in terms of collagen fiber orientation and crystallization. Liver samples obtained from autopsy cases with fibrosis stage of F0-F4 were evaluated with an SHG microscope, and 12 consecutive PR-SHG images were acquired while changing the polarization azimuth angle of the irradiated laser from 0° to 165° in 15° increments using polarizer. The fiber orientation angle (φ) and degree (ρ) of collagen were estimated from the images. The SHG-positive area increased as the fibrosis stage progressed, which was well consistent with Sirius Red staining. The value of φ was random regardless of fibrosis stage. The mean value of ρ (ρ-mean), which represents collagen fiber crystallinity, varied more as fibrosis progressed to stage F3, and converged to a significantly higher value in F4 than in other stages. Spatial dispersion of ρ (ρ-entropy) also showed increased variation in the stage F3 and decreased variation in the stage F4. It was shown that PR-SHG could provide new information on the properties of collagen fibers in human liver fibrosis.

Hyperoside attenuates carbon tetrachloride-induced hepatic fibrosis via the poly(ADP-ribose)polymerase-1-high mobility group protein 1 pathway

Oxidative stress and inflammation have been implicated in hepatic fibrosis. Antioxidant and anti-inflammatory activities are among the pharmacological effects of hyperoside. This study aimed to evaluate the impact of hyperoside on hepatic fibrosis and elucidate the underlying processes that perpetuate this relationship. The findings indicated that hyperoside significantly protects mouse livers against damage, inflammation, and fibrosis. Specifically, attenuation of hepatic fibrosis is associated with lower expression of HMGB1 protein and reduced expression of Toll-like receptor 4, PARP-1, and nuclear factor-kB (NF-κB) p65 mRNA and protein. Furthermore, hyperoside inhibited the cytoplasmic translocation of HMGB1 and nuclear localization of NF-κB p65 in the hepatic tissues of mice. The results of this study indicate that hyperoside may impose a blocking or reversing effect on hepatic fibrosis; additionally, the corresponding hyperoside-dependent mechanism may be linked to PARP-1-HMGB1 pathway regulation.

Magnetic resonance elastography for noninvasive detection of liver fibrosis: is there an added value of 3D acquisition?

PURPOSE

(1) Assess the diagnostic performance of liver 3D magnetic resonance elastography (MRE) parameters (including stiffness, storage/loss modulus and damping ratio) compared to liver stiffness measured with 2D MRE for noninvasive detection of advanced liver fibrosis (F3-F4) and cirrhosis (F4) in patients with chronic liver disease. (2) Assess the value of serum markers (FIB-4) in detecting advanced liver fibrosis and cirrhosis in the same patients.

METHODS

This was a single center, prospective IRB-approved cross-sectional study that included 49 patients (M/F: 23/26, mean age 50.8 y) with chronic liver disease and concomitant liver biopsy. MRE was acquired at 1.5T using a spin echo-EPI sequence. The following parameters were measured: liver stiffness using 2D MRE (LS-2D) and 3D MRE parameters (LS-3D, liver storage, loss modulus and damping ratio). The Mann-Whitney U test, ROC curve analysis, Spearman correlation and logistic regression were performed to evaluate diagnostic performance of MRE parameters and FIB-4.

RESULTS

LS-2D and LS-3D had similar diagnostic performance for diagnosis of F3-F4, with AUCs of 0.87 and 0.88, sensitivity of 0.71 and 0.81, specificity of 0.89 for both. For diagnosis of F4, LS-2D and LS-3D had similar performance with AUCs of 0.81 for both, sensitivity of 0.75 and 0.83, and specificity of 0.84 and 0.73, respectively. Additional 3D parameters (storage modulus, loss modulus, damping ratio) had variable performance, with AUC range of 0.59-0.78 for F3-F4; and 0.52-0.70 for F4. FIB-4 had lower diagnostic performance, with AUCs of 0.66 for F3-F4, and 0.68 for F4.

CONCLUSION

Our study shows no added value of 3D MRE compared to 2D MRE for detection of advanced fibrosis and cirrhosis, while FIB-4 had lower diagnostic performance.

Segmentation algorithm can be used for detecting hepatic fibrosis in SD rat

BACKGROUND

Liver fibrosis is an early stage of liver cirrhosis. As a reversible lesion before cirrhosis, liver failure, and liver cancer, it has been a target for drug discovery. Many antifibrotic candidates have shown promising results in experimental animal models; however, due to adverse clinical reactions, most antifibrotic agents are still preclinical. Therefore, rodent models have been used to examine the histopathological differences between the control and treatment groups to evaluate the efficacy of anti-fibrotic agents in non-clinical research. In addition, with improvements in digital image analysis incorporating artificial intelligence (AI), a few researchers have developed an automated quantification of fibrosis. However, the performance of multiple deep learning algorithms for the optimal quantification of hepatic fibrosis has not been evaluated. Here, we investigated three different localization algorithms, mask R-CNN, DeepLabV3⁺, and SSD, to detect hepatic fibrosis.

RESULTS

5750 images with 7503 annotations were trained using the three algorithms, and the model performance was evaluated in large-scale images and compared to the training images. The results showed that the precision values were comparable among the algorithms. However, there was a gap in the recall, leading to a difference in model accuracy. The mask R-CNN outperformed the recall value (0.93) and showed the closest prediction results to the annotation for detecting hepatic fibrosis among the algorithms. DeepLabV3⁺ also showed good performance; however, it had limitations in the misprediction of hepatic fibrosis as inflammatory cells and connective tissue. The trained SSD showed the lowest performance and was limited in predicting hepatic fibrosis compared to the other algorithms because of its low recall value (0.75).

CONCLUSIONS

We suggest it would be a more useful tool to apply segmentation algorithms in implementing AI algorithms to predict hepatic fibrosis in non-clinical studies.

Computed tomography imaging features to evaluate the severity of portal hypertension and predict the rebleeding risk after endoscopic treatment in cirrhotic patients with variceal hemorrhage

PURPOSE

To investigate the association of computed tomography (CT) imaging features and severity of portal hypertension (PH) and develop a nomogram to predict high-risk PH in cirrhotic patients with gastroesophageal variceal hemorrhage (GVH).

METHODS

The study retrospectively enrolled 158 cirrhotic patients with a history of endoscopic treatment for GVH. Hepatic vein pressure gradient (HVPG) was measured and the patients were classified into high-risk (HVPG > 16 mmHg) or low-risk (HVPG ≤ 16 mmHg) PH group. Pre-treatment CT features, including cavernous transformation of portal vein (CTPV), hilar periportal space (a distance between right portal vein and posterior edge of segment IV of the liver), and depth of right posterior hepatic notch sign (a sharp indentation in the right medial posterior liver surface), were evaluated. Risk factors associated with high-risk PH were analyzed, and a nomogram based on the imaging features was developed.

RESULTS

High-risk PH group showed a higher rebleeding rate after treatment than that of the low-risk (P = 0.029). Multivariate analysis indicated that larger hilar periportal space (P < 0.001), less frequencies of CTPV (P = 0.044) and deeper right posterior hepatic notch (P < 0.001) were independent risk factors associated with high-risk PH. A nomogram based on the three CT imaging features was established to predict high-risk PH with an excellent discrimination (c-statistic 0.854).

CONCLUSION

The nomogram based on CT features of hilar periportal space, depth of right posterior hepatic notch and CTPV can help to distinguish cirrhotic patients with high-risk PH, who are more vulnerable of variceal rebleeding after endoscopic treatment.

Unpaired virtual histological staining using prior-guided generative adversarial networks

Fibrosis is an inevitable stage in the development of chronic liver disease and has an irreplaceable role in characterizing the degree of progression of chronic liver disease. Histopathological diagnosis is the gold standard for the interpretation of fibrosis parameters. Conventional hematoxylin-eosin (H&E) staining can only reflect the gross structure of the tissue and the distribution of hepatocytes, while Masson trichrome can highlight specific types of collagen fiber structure, thus providing the necessary structural information for fibrosis scoring. However, the expensive costs of time, economy, and patient specimens as well as the non-uniform preparation and staining process make the conversion of existing H&E staining into virtual Masson trichrome staining a solution for fibrosis evaluation. Existing translation approaches fail to extract fiber features accurately enough, and the decoder of staining is unable to converge due to the inconsistent color of physical staining. In this work, we propose a prior-guided generative adversarial network, based on unpaired data for effective Masson trichrome stained image generation from the corresponding H&E stained image. Conducted on a small training set, our method takes full advantage of prior knowledge to set up better constraints on both the encoder and the decoder. Experiments indicate the superior performance of our method that surpasses the previous approaches. For various liver diseases, our results demonstrate a high correlation between the staging of real and virtual stains (ρ=0.82; 95% CI: 0.73-0.89). In addition, our finetuning strategy is able to standardize the staining color and release the memory and computational burden, which can be employed in clinical assessment.

Collagen is More Abundant and Structurally Altered in Lichen Sclerosus

OBJECTIVE

To test the hypothesis that genital skin and male urethra affected by lichen sclerosus (LS) has increased collagen content and altered collagen structure.

METHODS

We used picrosirius red to stain and image collagen in human urethral, vulvar, and foreskin specimens with and without LS. Using Image J software, we quantified and compared (1) collagen content (using 2o metrics: collagen proportionate area [CPA] and collagen fiber count), (2) collagen fiber length and width, and (3) collagen structure using the texture analysis technique gray level co-localization matrix (GLCM) with respect to LS status and tissue type.

RESULTS

We analyzed 23 LS specimens (vulva n=9, urethra n=7, foreskin n=7) and 29 non-LS specimens (vulva n=9, urethra n=7, foreskin n=13). Fiber count and CPA were significantly higher in all LS specimens compared to non-LS specimens (CPA: mean±SD 0.971±0.03 vs 0.948±0.02, P < .007; fiber count: mean±SD = 2906±127 vs 2509±78 fibers; P = .003). Collagen fiber width and length were similar with respect to LS status. GLCM analysis showed decreased inverse difference moment and increased entropy in LS tissues indicative of less homogeneous and more disorganized tissue structure (P<.001).

CONCLUSION

LS tissues have greater collagen content compared to non-LS tissues. Quantitative assessment of collagen organization, using GLCM, revealed less homogeneity and more disorganization of collagen in LS compared to non-LS tissues. Taken together, our findings suggest that alterations in physical tissue properties seen in LS may be due to both increased collagen abundance and altered structure.

Artificial intelligence and deep learning: new tools for histopathological diagnosis of nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) is associated with metabolic syndrome and is rapidly increasing globally with the increased prevalence of obesity. Although noninvasive diagnosis of NAFLD/NASH has progressed, pathological evaluation of liver biopsy specimens remains the gold standard for diagnosing NAFLD/NASH. However, the pathological diagnosis of NAFLD/NASH relies on the subjective judgment of the pathologist, resulting in non-negligible interobserver variations. Artificial intelligence (AI) is an emerging tool in pathology to assist diagnoses with high objectivity and accuracy. An increasing number of studies have reported the usefulness of AI in the pathological diagnosis of NAFLD/NASH, and our group has already used it in animal experiments. In this minireview, we first outline the histopathological characteristics of NAFLD/NASH and the basics of AI. Subsequently, we introduce previous research on AI-based pathological diagnosis of NAFLD/NASH.

Non-alcoholic fatty liver disease: the pathologist's perspective

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of diseases characterized by fatty accumulation in hepatocytes, ranging from steatosis, non-alcoholic steatohepatitis, to cirrhosis. While histopathological evaluation of liver biopsies plays a central role in the diagnosis of NAFLD, limitations such as the problem of interobserver variability still exist and active research is underway to improve the diagnostic utility of liver biopsies. In this article, we provide a comprehensive overview of the histopathological features of NAFLD, the current grading and staging systems, and discuss the present and future roles of liver biopsies in the diagnosis and prognostication of NAFLD.

Diagnosis of Clinically Significant Portal Hypertension Using CT- and MRI-based Vascular Model

Background Currently, the hepatic venous pressure gradient (HVPG) remains the reference standard for diagnosis of clinically significant portal hypertension (CSPH) but is limited by its invasiveness and availability. Purpose To investigate a vascular geometric model for noninvasive diagnosis of CSPH (HVPG ≥10 mm Hg) in patients with liver cirrhosis for both contrast-enhanced CT and MRI. Materials and Methods In this retrospective study, consecutive patients with liver cirrhosis who underwent HVPG measurement from August 2016 to April 2019 were included. Patients without hepatic diseases were included and marked as non-CSPH to balance the ratio of CSPH 1:1. A variety of vascular parameters were extracted from the portal vein, hepatic vein, aorta, and inferior vena cava and then entered into a vascular geometric model for identification of CSPH. Diagnostic performance was assessed with the area under the receiver operating characteristic curve (AUC). Results The model was developed and tested with retrospective data from 250 patients with liver cirrhosis and 273 patients without clinical evidence of hepatic disease at contrast-enhanced CT examination, including 213 patients with CSPH (mean age, 49 years ± 12 [SD]; 138 women) and 310 patients without CSPH (mean age, 50 years ± 9; 177 women). For external validation, an MRI data set with 224 patients with cirrhosis (mean age, 49 years ± 10; 158 women) and a CT data set with 106 patients with cirrhosis (mean age, 53 years ± 12; 71 women) were analyzed. Significant reductions in mean whole-vessel volumes were observed in the portal vein (ranging from 36.9 cm³ ± 16.0 to 29.6 cm³ ± 11.1; P < .05) and hepatic vein (ranging from 35.3 cm³ ± 21.5 to 22.4 cm³ ± 15.7; P < .05) when CSPH occurred. Similarly, the mean whole-vessel lengths were shorter in patients with CSPH (portal vein: 1.7 m ± 1.2 vs 3.0 m ± 2.4, P < .05; hepatic vein: 0.9 m ± 1.5 vs 1.8 m ± 1.5, P < .05) than in those without CSPH. The proposed vascular model performed well in the internal test set (mean AUC, 0.90 ± 0.02) and external test sets (mean AUCs, 0.84 ± 0.12 and 0.87 ± 0.11). Conclusion A contrast-enhanced CT- and MRI-based vascular model was proposed with good diagnostic consistency for hepatic venous pressure gradient measurement. ClinicalTrials.gov registration nos. NCT03138915 and NCT03766880 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Roldán-Alzate and Reeder in this issue.

Phosphotungstic Acid-treated Picrosirius Red Staining Improves Whole-slide Quantitative Analysis of Collagen in Histological Specimens

We tried to prevent nonspecific nuclear staining (NS-NS) of picrosirius red (PSR) staining by treating the specimens with one of the heteropoly acids phosphotungstic acid (PTA). We analyzed a total of 35 cases of non-cancerous liver tissue for fibrosis and NS-NS under PSR-alone, phosphomolybdic acid (PMA)-pretreated PSR (PMA + PSR), or PTA-pretreated PSR (PTA + PSR) condition. In addition, we analyzed the photosensitivity of PMA or PTA single stain specimens. PTA + PSR significantly suppressed NS-NS compared with PSR. The color of the specimens did not change into blue by 30 times the exposure to whole slide scanner (WSS) light. The PTA + PSR condition showed the highest correlation with the Ishak score (pathological evaluation of liver fibrosis) compared with other conditions. Furthermore, Sirius Red-positive percentage (SRP%) in PSR was increased in the NS-NS observed cases. SRP% in PMA + PSR was significantly affected by WSS light exposure time. Moreover, the deposition of non-polarized PSR-stained substances (NP-PSR+S) clinging to the collagen fibers potentially explains why SRP% seemed bigger under PSR than PTA + PSR. Our protocol enabled us to analyze the whole slide image of PSR staining by high magnification, which would contribute to the accurate analysis of collagen amount in the tissue sections.

Staging Liver Fibrosis by Fibroblast Activation Protein Inhibitor PET in a Human-Sized Swine Model

Current methods of staging liver fibrosis have notable limitations. We investigated the utility of PET in staging liver fibrosis by correlating liver uptake of ⁶⁸Ga-labeled fibroblast activation protein inhibitor (FAPI) with histology in a human-sized swine model. Methods: Five pigs underwent baseline ⁶⁸Ga-FAPI-46 (⁶⁸Ga-FAPI) PET/MRI and liver biopsy, followed by liver parenchymal embolization, 8 wk of oral alcohol intake, endpoint ⁶⁸Ga-FAPI PET/MRI, and necropsy. Regions of interest were drawn on baseline and endpoint PET images, and SUV_mean was recorded. At the endpoint, liver sections corresponding to regions of interest were identified and cut out. Fibrosis was histologically evaluated using a modified METAVIR score for swine liver and quantitatively using collagen proportionate area (CPA). Box-and-whisker plots and linear regression were used to correlate SUV_mean with METAVIR score and CPA, respectively. Results: Liver ⁶⁸Ga-FAPI uptake strongly correlated with CPA (r = 0.89, P < 0.001). ⁶⁸Ga-FAPI uptake was significantly and progressively higher across F2 and F3/F4 fibrosis stages, with a respective median SUV_mean of 2.9 (interquartile range [IQR], 2.7-3.8) and 7.6 (IQR, 6.7-10.2) (P < 0.001). There was no significant difference between ⁶⁸Ga-FAPI uptake of baseline liver and endpoint liver sections staged as F0/F1, with a respective median SUV_mean of 1.7 (IQR, 1.3-2.0) and 1.7 (IQR, 1.5-1.8) (P = 0.338). Conclusion: The strong correlation between liver ⁶⁸Ga-FAPI uptake and the histologic stage of liver fibrosis suggests that ⁶⁸Ga-FAPI PET can play an impactful role in noninvasive staging of liver fibrosis, pending validation in patients.

Noninvasive Prediction of Advanced Fibrosis in Pediatric Liver Disease-Discriminatory Performance of 2D Shear Wave Elastography, Transient Elastography and Magnetic Resonance Elastography in Comparison to Histopathology

Background: Elastography can be measured with different imaging techniques and is increasingly used for noninvasive assessment of hepatic fibrosis. Little is known about the performance, and interrelation of different elastographic techniques, in prediction of hepatic fibrosis in pediatric liver disease. Objectives: We aimed to determine the discriminatory value for advanced fibrosis (Metavir F3-4) and evaluate the applicability of 2D shear wave ultrasound elastography (USe), Transient Elastography (TE) and Magnetic Resonance elastography (MRe) in pediatric liver disease. Methods: In patients with pediatric liver disease aged 0−19 years, USe, TE and MRe were compared with histopathological fibrosis stage. Multivariate logistic regression models for advanced fibrosis were considered. Discriminative performance was assessed by the area under the receiver operating characteristic curve and the Brier Score. Primary analyses included complete cases. Multiple imputation was used as sensitivity analysis. Results: In 93 histologically evaluated patients USe, TE and MRe were performed 89, 93 and 61 times respectively. With increased liver stiffness values, significantly increased odds for presenting F3-4 were seen in individual models for ALT < 470 U/L, whereas the effect for ALT > 470 U/L was non-significant. Area under the curve and Brier Score for discrimination of advanced fibrosis were 0.798 (0.661−0.935) and 0.115 (0.064−0.166); 0.862 (0.758−0.966) and 0.118 (0.065−0.171); 0.896 (0.798−0.994) and 0.098 (0.049−0.148) for USe, TE and MRe respectively. No significant increase in discriminatory ability was found when combining elastographic modalities. Conclusions: In pediatric liver disease, USe, TE and MRe had a good discriminatory ability for assessment of advanced liver fibrosis, although TE and MRe performed best. In most children with pediatric liver disease, TE is a reliable and easily applicable measure.

Clinical Outcomes in Patients with Advanced Chronic Liver Disease and Hepatic Venous Pressure Gradient ≤ 10 mm Hg

BACKGROUND AND AIMS

Clinically significant portal hypertension (CSPH), defined as hepatic venous pressure gradient (HVPG) ≥ 10 mmHg predicts clinical decompensation (CD) in cirrhosis. A proportion of cirrhosis patients have HVPG 6-10 mmHg. Their natural history is largely unknown.

DESIGN

Consecutive patients with advanced chronic liver disease (aCLD) [histological cirrhosis(n = 196) or liver stiffness measurement (LSM) > 15 kPa(n = 65)] and HVPG 6-10 mmHg were included. Primary objective was to study their natural course and patterns of CD. We also analyzed the predictors of CD at presentation and on follow-up and response to carvedilol.

RESULTS

Of 261 patients with HVPG 6-10 mmHg, 129(49.4%) had CD at first presentation; 78(29.9%) had single and 51(19.5%) had ≥ 2 CD. The most common CDs were ascites(n = 77) and jaundice(n = 65). A baseline HVPG ≥ 8 mmHg was independently associated with greater risk of CD [HR:1.7; p-0.002, AUROC:0.85(95%CI-0.81-0.91)]. New CD developed in 14.4% patients with compensated aCLD (median duration-23.1 months). Despite comparable baseline HVPG, patients developing new CD had higher HVPG on follow-up(15.3 ± 3.7 vs. 8 ± 2.1 mmHg; p < 0.001). Baseline LSM > 26.6 kPa, portosystemic shunt and serum albumin independently predicted new CD. Overall HVPG response to carvedilol(n = 60) was 23.3%, independent of baseline CD and HVPG. Five-year mortality was higher with ≥ 2 CD compared to single or no CD (23.5, 10 and 3%, respectively; p < 0.001).

CONCLUSION

Nearly one-half of aCLD patients with HVPG 6-10 mmHg had CD, justifying the need to redefine CSPH. Interventions to reduce portal pressure in patients with HVPG ≥ 8 mmHg might improve long-term outcomes.

Pathogenic effects of Desulfovibrio in the gut on fatty liver in diet-induced obese mice and children with obesity

BACKGROUND

Although we know the key role of gut dysbiosis in nonalcoholic fatty liver disease (NAFLD), it remains unclear what microbe(s) are responsible. This study aims to identify the microbes that cause NAFLD.

METHODS

C57BL/6JNarl male mice fed a high-fat diet (HFD) were orally administered Lactobacillus reuteri (L. reuteri) or Lactobacillus rhamnosus GG plus Bifidobacterium animalis subsp. lactis BB12 (LGG plus BB12). Their fecal microbiomes identified by 16S rRNA sequencing were correlated with the severity of fatty liver. We then used a human cohort to confirm the role of the microbe(s). The HFD-fed mice were administrated with the identified bacterium, Desulfovibrio. The histopathological changes in the liver and ileum were analyzed.

RESULTS

Lactobacillus and Bifidobacterium improved hepatic steatosis and fibrosis in HFD-fed mice, which was related to the decreased abundance of Desulfovibrio in feces. Further human study confirmed the amount of D. piger in the fecal microbiota of obese children with NAFLD was increased. We then administered D. piger and found aggravated hepatic steatosis and fibrosis in HFD-fed mice. Hepatic expression of CD36 was significantly increased in HFD-fed mice gavaged with D. piger. In HepG2 cells, overexpression of CD36 increased lipid droplets, whereas knockdown of CD36 decreased lipid droplets. HFD-fed mice gavaged with D. piger had a decrease in the villus length, crypt depth, and zonula occludens-1 density in the ileum tissue.

CONCLUSIONS

Our findings provide novel insights into the role of Desulfovibrio dysregulation in NAFLD. Modulation of Desulfovibrio may be a potential target for the treatment of NAFLD.

Liver and spleen volumes are associated with prognosis of compensated and decompensated cirrhosis and parallel its natural history

Objective

Cirrhosis is characterized by the complex interplay among biological, histological and haemodynamic events. Liver and spleen remodelling occur throughout its natural history, but the prognostic role of these volumetric changes is unclear. We evaluated the relationship between volumetric changes assessed by multidetector computerised tomography (MDCT) and landmark features of cirrhosis.

Methods

We included consecutive cirrhotic patients who underwent liver transplantation (LT) or hepatocellular carcinoma (HCC) resection in whom dynamic MDCT was available. Different volumetric indices were calculated. Fibrosis was evaluated by the collagen proportional area and Laennec sub‐stages. Correlation and logistic regression analysis were performed to explore associations of volumetric indexes and fibrosis with key prognostic features across the clinical stages of cirrhosis.

Results

185 patients were included (146 LT; 39 HCC); the predominant aetiology was viral hepatitis (51.35%); 65.9% had decompensated disease and 85.08% clinically significant portal hypertension (CSPH). The standardised liver volume and liver‐spleen volume ratio negatively correlated with Model for End‐stage Liver Disease (MELD), albumin and hepatic venous pressure gradient (HVPG) and were significantly lower in decompensated patients. The liver segmental volume ratio (segments I–III/segments IV–VIII) best captured the characteristic features of the compensated phase, showing a positive correlation with HVPG and a good discrimination between patients with and without CSPH and varices. Volumetric changes and fibrosis severity were independently associated with key prognostic events, with no association between these two parameters.

Conclusions

Liver and spleen volumetric indices evolve differently along the natural history of cirrhosis and are associated with key prognostic factors in each phase, regardless of fibrosis severity and portal hypertension.

MR elastography outperforms shear wave elastography for the diagnosis of clinically significant portal hypertension

OBJECTIVES

Portal hypertension (PH) is associated with complications such as ascites and esophageal varices and is typically diagnosed through invasive hepatic venous pressure gradient (HVPG) measurement, which is not widely available. In this study, we aim to assess the diagnostic performance of 2D/3D MR elastography (MRE) and shear wave elastography (SWE) measures of liver and spleen stiffness (LS and SS) and spleen volume, to noninvasively diagnose clinically significant portal hypertension (CSPH) using HVPG measurement as the reference.

METHODS

In this prospective study, patients with liver disease underwent 2D/3D MRE and SWE of the liver and spleen, as well as HVPG measurement. The correlation between MRE/SWE measures of LS/SS and spleen volume with HVPG was assessed. ROC analysis was used to determine the utility of MRE, SWE, and spleen volume for diagnosing CSPH.

RESULTS

Thirty-six patients (M/F 22/14, mean age 55 ± 14 years) were included. Of the evaluated parameters, 3D MRE SS had the strongest correlation with HVPG (r = 0.686, p < 0.001), followed by 2D MRE SS (r = 0.476, p = 0.004). 3D MRE SS displayed the best performance for diagnosis of CSPH (AUC = 0.911) followed by 2D MRE SS (AUC = 0.845) and 3D MRE LS (AUC = 0.804). SWE SS showed poor performance for diagnosis of CSPH (AUC = 0.583) while spleen volume was a fair predictor (AUC = 0.738). 3D MRE SS was significantly superior to SWE LS/SS (p ≤ 0.021) for the diagnosis of CSPH.

CONCLUSION

SS measured with 3D MRE outperforms SWE for the diagnosis of CSPH. SS appears to be a useful biomarker for assessing PH severity. These results need further validation.

KEY POINTS

• Spleen stiffness measured with 2D and 3D MR elastography correlates significantly with hepatic venous pressure gradient measurement. • Spleen stiffness measured with 3D MR elastography demonstrates excellent performance for the diagnosis of clinically significant portal hypertension (AUC 0.911). • Spleen stiffness measured with 3D MR elastography outperforms liver and spleen stiffness measured with shear wave elastography for diagnosis of clinically significant portal hypertension.

Expression of IL-37 Correlates With Immune Cell Infiltrate and Fibrosis in Pediatric Autoimmune Liver Diseases

OBJECTIVES

The activation of innate immune mechanisms is key for chronic liver injury. Interleukin-37 (IL-37) is a profound inhibitor of innate and adaptive immune responses, and its overexpression protects mice from liver inflammation and fibrosis. Here, we characterize the hepatic inflammatory infiltrate and expression of IL-37 in children with autoimmune liver diseases.

METHODS

We compared the inflammatory microenvironment of the liver in a retrospective cohort of children with primary sclerosing cholangitis (PSC), autoimmune sclerosing cholangitis (ASC) and autoimmune hepatitis (AIH) by immunohistochemistry. The expression of IL-37 was quantified in liver parenchyma and portal tracts. Double immunofluorescence was used for detection of IL-37 in specific cell types and colocalization with Smad3.

RESULTS

AIH is characterized by a dense lymphoplasmacytic infiltrate whereas ASC shows high numbers of granulocytes in portal tracts. IL-37 expression correlates positively with liver inflammation and fibrosis, the number of infiltrating immune cells and serum markers for hepatic inflammation. IL-37 is mainly expressed in hepatocytes, cholangiocytes and infiltrating immune cells. Double staining revealed IL-37 positivity in T helper and regulatory T cells (Treg), Kupffer (KC) and hepatic stellate cells (HSC). IL-37 colocalizes with intranuclear pSmad3L in areas of liver inflammation.

CONCLUSIONS

Pediatric ASC separates from PSC and AIH by a granulocyte-rich portal infiltrate. Upregulation of IL-37 with liver injury, the expression in Treg as well as KC and HSC and the colocalization of IL-37 with pSmad3L in cholangiocytes and hepatocytes suggest a modulating role to limit hepatic inflammation and fibrosis in pediatric autoimmune liver diseases.

Collagen proportionate area predicts long-term mortality in patients with alcoholic hepatitis

BACKGROUND AND AIMS

There are several short-term prognostic scores for alcoholic hepatitis (AH) that combine demographical and biochemical parameters. The extent of liver fibrosis may also be relevant to the prognosis of AH with potential added value. We evaluated collagen proportionate area (CPA) as a predictor of short and long-term mortality in AH.

METHODS

We retrospectively included patients with biopsy-verified AH. Clinical, laboratory and outcome data were collected. CPA and five AH scores were calculated: Maddrey's DF, MELD, GAHS, ABIC, and the Lille Model. Predictors of short and long-term all-cause mortality were assessed using Cox regression analysis.

RESULTS

We included 140 patients with AH. In total, 67 (48%) patients died after a median follow-up of 66 (IQR 102) months, with 17 (12%) dying within the first 90-days. CPA was not a predictor of 90-days mortality and had no additional value to the prognostic AH scores on short-term mortality. However, CPA predicted long-term mortality independently of prognostic AH scores. Importantly, CPA and abstinence from alcohol were independent predictors of long-term mortality in patients alive 90 days after the biopsy.

CONCLUSION

CPA predicts long-term mortality in patients with AH independently of abstinence from alcohol but has no prognostic value on short-term mortality.

Distinct structural and dynamic components of portal hypertension in different animal models and human liver disease etiologies

BACKGROUND AND AIMS

Liver fibrosis is the static and main (70%-80%) component of portal hypertension (PH). We investigated dynamic components of PH by a three-dimensional analysis based on correlation of hepatic collagen proportionate area (CPA) with portal pressure (PP) in animals or HVPG in patients.

APPROACH AND RESULTS

Different animal models (bile duct ligation: n = 31, carbon tetrachloride: n = 12, thioacetamide: n = 12, choline-deficient high-fat diet: n = 12) and patients with a confirmed single etiology of cholestatic (primary biliary cholangitis/primary sclerosing cholangitis: n = 16), alcohol-associated (n = 22), and metabolic (NASH: n = 19) liver disease underwent CPA quantification on liver specimens/biopsies. Based on CPA-to-PP/HVPG correlation, potential dynamic components were identified in subgroups of animals/patients with lower-than-expected and higher-than-expected PP/HVPG. Dynamic PH components were validated in a patient cohort (n = 245) using liver stiffness measurement (LSM) instead of CPA. CPA significantly correlated with PP in animal models (Rho = 0.531; p < 0.001) and HVPG in patients (Rho = 0.439; p < 0.001). Correlation of CPA with PP/HVPG varied across different animal models and etiologies in patients. In models, severity of hyperdynamic circulation and specific fibrosis pattern (portal fibrosis: p = 0.02; septa width: p = 0.03) were associated with PH severity. In patients, hyperdynamic circulation (p = 0.04), vascular dysfunction/angiogenesis (VWF-Ag: p = 0.03; soluble vascular endothelial growth factor receptor 1: p = 0.03), and bile acids (p = 0.04) were dynamic modulators of PH. The LSM-HVPG validation cohort confirmed these and also indicated IL-6 (p = 0.008) and hyaluronic acid (HA: p < 0.001) as dynamic PH components.

CONCLUSIONS

The relative contribution of "static" fibrosis on PH severity varies by type of liver injury. Next to hyperdynamic circulation, increased bile acids, VWF-Ag, IL-6, and HA seem to indicate a pronounced dynamic component of PH in patients.

Use of the volume-averaged Murray's deviation method for the characterization of branching geometry in liver fibrosis: a preliminary study on vascular circulation

Background

Vascular changes in liver fibrosis can result in increased intrahepatic vascular resistance and impaired blood circulation. This can hinder the recovery from fibrosis and may eventually lead to portal hypertension, a major cirrhosis complication. This report proposed a volume-averaged Murray's deviation method to characterize intrahepatic circulation in the liver during fibrosis and its subsequent regression via X-ray phase-contrast computed tomography (PCCT).

Methods

Liver fibrosis was induced in 24 Sprague-Dawley rats by exposure to carbon tetrachloride (CCl₄) for up to 10 weeks, after which, spontaneous regression commenced and continued until week 30. High-resolution three-dimensional (3D) imaging of the livers was performed with PCCT. The values of Murray's deviation based on the volume-averaged and the conventional diameter-based methods were compared. After that, the intrahepatic circulation at different stages of fibrosis was evaluated using the volume-averaged method. The increase in collagen during liver fibrosis was assessed by pathological analyses.

Results

A comparison of the 2 methods showed that with an increase in the number of diameter measurements, the value of Murrary's deviation obtained using the diameter-based method gradually approaches those of the volume-averaged method, with minimal variations. The value of Murray's deviation increased with the development of fibrosis. After reversal, the value rapidly decreased and approached that of the normal state in both the main branches (1.05±0.17, 1.17±0.21, 1.34±0.18, and 1.17±0.19 in the normal, moderate, severe, and regressive groups, respectively; P<0.05 between the severe group and other groups) and the small branches (1.05±0.09, 1.42±0.48, 1.79±0.57, and 1.18±0.28 in the normal, moderate, severe, and regressive group, respectively; P<0.05 between adjacent groups). An analysis of Murray's deviation and the pathological results showed that the vascular circulation in this disease model was consistent with the progression and recovery from fibrosis.

Conclusions

This study showed the validity of the volume-averaged method for calculating Murray's deviation and demonstrated that it could accurately evaluate the blood circulation state of the liver during fibrosis and its subsequent regression. Thus, the volume-averaged method of calculating Murray's deviation may be an objective and valuable staging criterion to evaluate intrahepatic circulation during liver fibrosis.

Comparative diagnostic performance of ultrasound shear wave elastography and magnetic resonance elastography for classifying fibrosis stage in adults with biopsy-proven nonalcoholic fatty liver disease

Objectives

To compare the diagnostic accuracy of US shear wave elastography (SWE) and magnetic resonance elastography (MRE) for classifying fibrosis stage in patients with nonalcoholic fatty liver disease (NAFLD).

Methods

Patients from a prospective single-center cohort with clinical liver biopsy for known or suspected NAFLD underwent contemporaneous SWE and MRE. AUCs for classifying biopsy-determined liver fibrosis stages ≥ 1, ≥ 2, ≥ 3, and = 4, and their respective performance parameters at cutoffs providing ≥ 90% sensitivity or specificity were compared between SWE and MRE.

Results

In total, 100 patients (mean age, 51.8 ± 12.9 years; 46% males; mean BMI 31.6 ± 4.7 kg/m²) with fibrosis stage distribution (stage 0/1/2/3/4) of 43, 36, 5, 10, and 6%, respectively, were included. AUCs (and 95% CIs) for SWE and MRE were 0.65 (0.54–0.76) and 0.81 (0.72–0.89), 0.81 (0.71–0.91) and 0.94 (0.89–1.00), 0.85 (0.74–0.96) and 0.95 (0.89–1.00), and 0.91 (0.79–1.00) and 0.92 (0.83–1.00), for detecting fibrosis stage ≥ 1, ≥ 2, ≥ 3, and = 4, respectively. The differences were significant for detecting fibrosis stage ≥ 1 and ≥ 2 (p < 0.01) but not otherwise. At ≥ 90% sensitivity cutoff, MRE yielded higher specificity than SWE at diagnosing fibrosis stage ≥ 1, ≥ 2, and ≥ 3. At ≥ 90% specificity cutoff, MRE yielded higher sensitivity than SWE at diagnosing fibrosis stage ≥ 1 and ≥ 2.

Conclusions

In adults with NAFLD, MRE was more accurate than SWE in diagnosing stage ≥ 1 and ≥ 2 fibrosis, but not stage ≥ 3 or 4 fibrosis.

Key Points

• For detecting any fibrosis or mild fibrosis, MR elastography was significantly more accurate than shear wave elastography.

• For detecting advanced fibrosis and cirrhosis, MRE and SWE did not differ significantly in accuracy.

• For excluding advanced fibrosis and potentially ruling out the need for biopsy, SWE and MRE did not differ significantly in negative predictive value.

• Neither SWE nor MRE had sufficiently high positive predictive value to rule in advanced fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-021-08369-9.

Digital Pathology Enables Automated and Quantitative Assessment of Inflammatory Activity in Patients with Chronic Liver Disease

Traditional histological evaluation for grading liver disease severity is based on subjective and semi-quantitative scores. We examined the relationship between digital pathology analysis and corresponding scoring systems for the assessment of hepatic necroinflammatory activity. A prospective, multicenter study including 156 patients with chronic liver disease (74% nonalcoholic fatty liver disease-NAFLD, 26% chronic hepatitis-CH etiologies) was performed. Inflammation was graded according to the Nonalcoholic Steatohepatitis (NASH) Clinical Research Network system and METAVIR score. Whole-slide digital image analysis based on quantitative (I-score: inflammation ratio) and morphometric (C-score: proportionate area of staining intensities clusters) measurements were independently performed. Our data show that I-scores and C-scores increase with inflammation grades (p < 0.001). High correlation was seen for CH (ρ = 0.85-0.88), but only moderate for NAFLD (ρ = 0.5-0.53). I-score (p = 0.008) and C-score (p = 0.002) were higher for CH than NAFLD. Our MATLAB algorithm performed better than QuPath software for the diagnosis of low-moderate inflammation (p < 0.05). C-score AUC for classifying NASH was 0.75 (95%CI, 0.65-0.84) and for moderate/severe CH was 0.99 (95%CI, 0.97-1.00). Digital pathology measurements increased with fibrosis stages (p < 0.001). In conclusion, quantitative and morphometric metrics of inflammatory burden obtained by digital pathology correlate well with pathologists' scores, showing a higher accuracy for the evaluation of CH than NAFLD.

A Machine Learning Approach to Liver Histological Evaluation Predicts Clinically Significant Portal Hypertension in NASH Cirrhosis

BACKGROUND AND AIMS

The hepatic venous pressure gradient (HVPG) is the standard for estimating portal pressure but requires expertise for interpretation. We hypothesized that HVPG could be extrapolated from liver histology using a machine learning (ML) algorithm.

APPROACH AND RESULTS

Patients with NASH with compensated cirrhosis from a phase 2b trial were included. HVPG and biopsies from baseline and weeks 48 and 96 were reviewed centrally, and biopsies evaluated with a convolutional neural network (PathAI, Boston, MA). Using trichrome-stained biopsies in the training set (n = 130), an ML model was developed to recognize fibrosis patterns associated with HVPG, and the resultant ML HVPG score was validated in a held-out test set (n = 88). Associations between the ML HVPG score with measured HVPG and liver-related events, and performance of the ML HVPG score for clinically significant portal hypertension (CSPH) (HVPG ≥ 10 mm Hg), were determined. The ML-HVPG score was more strongly correlated with HVPG than hepatic collagen by morphometry (ρ = 0.47 vs. ρ = 0.28; P < 0.001). The ML HVPG score differentiated patients with normal (0-5 mm Hg) and elevated (5.5-9.5 mm Hg) HVPG and CSPH (median: 1.51 vs. 1.93 vs. 2.60; all P < 0.05). The areas under receiver operating characteristic curve (AUROCs) (95% CI) of the ML-HVPG score for CSPH were 0.85 (0.80, 0.90) and 0.76 (0.68, 0.85) in the training and test sets, respectively. Discrimination of the ML-HVPG score for CSPH improved with the addition of a ML parameter for nodularity, Enhanced Liver Fibrosis, platelets, aspartate aminotransferase (AST), and bilirubin (AUROC in test set: 0.85; 95% CI: 0.78, 0.92). Although baseline ML-HVPG score was not prognostic, changes were predictive of clinical events (HR: 2.13; 95% CI: 1.26, 3.59) and associated with hemodynamic response and fibrosis improvement.

CONCLUSIONS

An ML model based on trichrome-stained liver biopsy slides can predict CSPH in patients with NASH with cirrhosis.

Collagen proportionate area correlates with histological stage and predicts clinical events in primary sclerosing cholangitis

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease in need of accurate biomarkers for stratification and as surrogates for clinical endpoints in trials. Quantitative liver fibrosis assessment by collagen proportionate area (CPA) measurement has been demonstrated to correlate with clinical outcomes in chronic hepatitis C, alcohol-related and non-alcoholic fatty liver disease. We aimed to investigate the ability of CPA to quantify liver fibrosis and predict clinical events in PSC.

METHODS

Biopsies from 101 PSC patients from two European centres were retrospectively assessed by two expert pathologists in tandem, using grading (Ishak and Nakanuma) and staging (Ishak, Nakanuma, Ludwig) systems recently validated to predict clinical events in PSC. CPA was determined by image analysis of picro-Sirius red-stained sections following a standard protocol. We assessed the correlations between CPA, staging and grading and their associations with three outcomes: (1) time to PSC-related death, liver transplant or primary liver cancer; (2) liver transplant-free survival; (3) occurrence of cirrhosis-related clinical manifestations.

RESULTS

CPA correlated strongly with histological stage determined by each scoring system (P < .001) and was significantly associated with the three endpoints. Median time to endpoint-1, endpoint-2 and endpoint-3 was shorter in patients with higher CPA, on Kaplan-Meier analyses (P = .011, P = .034 and P = .001, respectively).

CONCLUSION

Quantitative fibrosis assessment by CPA has utility in PSC. It correlates with established histological staging systems and predicts clinical events. CPA may be a useful tool for staging fibrosis and for risk stratification in PSC and should be evaluated further within prospective clinical trials.

Thick Fibrous Septa on Liver Biopsy Specimens Predict the Development of Decompensation in Patients With Compensated Cirrhosis

OBJECTIVES

In compensated cirrhosis, thick fibrous septa and small nodules on liver biopsy specimens correlate with the presence of clinically significant portal hypertension (CSPH). In turn, CSPH is the strongest predictor of cirrhosis decompensation. The aim of the study was to correlate liver biopsy specimen characteristics with the development of decompensation in patients with compensated cirrhosis.

METHODS

Patients with compensated cirrhosis and a concurrent liver biopsy specimen were reviewed. Semiquantitative grading of septal thickness and nodule size was performed. Primary end point was development of clinical decompensation. In total, 168 patients (median age, 49 years; 76% men) were included in the study; the most common etiology was viral.

RESULTS

In a median follow-up of 50 months, 43 (26%) patients developed clinical decompensation (60% ascites, 16% encephalopathy, 12% variceal hemorrhage, 7% jaundice, and 5% mixed). On univariate analysis, septal width was significantly associated with decompensation, but nodule size was not. On multivariate analysis including model for end-stage liver disease score, serum albumin, and septal width, albumin and septal width were independent predictors of decompensation.

CONCLUSIONS

Histologic cirrhosis in compensated patients can be subclassified by severity based on septal thickness, with thick septa denoting worse prognosis.

Portal hypertension is the main driver of liver stiffness in advanced liver cirrhosis

Liver stiffness (LS) is a novel non-invasive parameter widely used in clinical hepatology. LS correlates with liver fibrosis stage in non-cirrhotic patients. In cirrhotic patients it also shows good correlation with Hepatic Venous Pressure Gradient (HVPG). Our aim was to assess the contribution of liver fibrosis and portal hypertension to LS in patients with advanced liver cirrhosis. Eighty-one liver transplant candidates with liver cirrhosis of various aetiologies underwent direct HVPG and LS measurement by 2D shear-wave elastography (Aixplorer Multiwave, Supersonic Imagine, France). Liver collagen content was assessed in the explanted liver as collagen proportionate area (CPA) and hydroxyproline content (HP). The studied cohort included predominantly patients with Child-Pugh class B and C (63/81, 77.8%), minority of patients were Child-Pugh A (18/81, 22.2%). LS showed the best correlation with HVPG (r=0.719, p< 0.001), correlation of LS with CPA (r=0.441, p< 0.001) and HP/Amino Acids (r=0.414, p< 0.001) was weaker. Both variables expressing liver collagen content showed good correlation with each other (r=0.574, p<0.001). Multiple linear regression identified the strongest association between LS and HVPG (p < 0.0001) and weaker association of LS with CPA (p = 0.01883). Stepwise modelling showed minimal increase in r2 after addition of CPA to HVPG (0.5073 vs. 0.5513). The derived formula expressing LS value formation is: LS = 2.48 + (1.29 x HVPG) + (0.26 x CPA). We conclude that LS is determined predominantly by HVPG in patients with advanced liver cirrhosis whereas contribution of liver collagen content is relatively low.

Semiautomated quantification of the fibrous tissue response to complex three-dimensional filamentous scaffolds using digital image analysis

Fibrosis represents a relevant response to the implantation of biomaterials, which occurs not only at the tissue-material interface (fibrotic encapsulation) but also within the void fraction of complex three-dimensional (3D) biomaterial constructions (fibrotic ingrowth). Usual evaluation of the biocompatibility mostly depicts fibrosis at the interface of the biomaterial using semiquantitative scores. Here, the relations between encapsulation and infiltrating fibrotic growth are poorly represented. Virtual pathology and digital image analysis provide new strategies to assess fibrosis in a more differentiated way. In this study, we adopted a method previously used to quantify fibrosis in visceral organs to the quantification of fibrosis to 3D biomaterials. In a proof-of-concept study, we transferred the "Collagen Proportionate Area" (CPA) analysis from hepatology to the field of biomaterials. As one task of an experimental animal study, we used CPA analysis to quantify the fibrotic ingrowth into a filamentous scaffold after subcutaneous implantation. We were able to demonstrate that the application of the CPA analysis is well suited as an additional fibrosis evaluation strategy for new biomaterial constructions. The CPA method can contribute to a better understanding of the fibrotic interactions between 3D scaffolds and the host tissue responses.

Extension of Collagen Deposition in COVID-19 Post Mortem Lung Samples and Computed Tomography Analysis Findings

Lung fibrosis has specific computed tomography (CT) findings and represents a common finding in advanced COVID-19 pneumonia whose reversibility has been poorly investigated. The aim of this study was to quantify the extension of collagen deposition and aeration in postmortem cryobiopsies of critically ill COVID-19 patients and to describe the correlations with qualitative and quantitative analyses of lung CT. Postmortem transbronchial cryobiopsy samples were obtained, formalin fixed, paraffin embedded and stained with Sirius red to quantify collagen deposition, defining fibrotic samples as those with collagen deposition above 10%. Lung CT images were analyzed qualitatively with a radiographic score and quantitatively with computer-based analysis at the lobe level. Thirty samples from 10 patients with COVID-19 pneumonia deceased during invasive mechanical ventilation were included in this study. The median [interquartile range] percent collagen extension was 6.8% (4.6-16.2%). In fibrotic compared to nonfibrotic samples, the qualitative score was higher (260 (250-290) vs. 190 (120-270), p = 0.036) while the gas fraction was lower (0.46 (0.32-0.47) vs. 0.59 (0.37-0.68), p = 0.047). A radiographic score above 230 had 100% sensitivity (95% confidence interval, CI: 66.4% to 100%) and 66.7% specificity (95% CI: 41.0% to 92.3%) to detect fibrotic samples, while a gas fraction below 0.57 had 100% sensitivity (95% CI: 66.4% to 100%) and 57.1% specificity (95% CI: 26.3% to 88.0%). In COVID-19 pneumonia, qualitative and quantitative analyses of lung CT images have high sensitivity but moderate to low specificity to detect histopathological fibrosis. Pseudofibrotic CT findings do not always correspond to increased collagen deposition.

Histological sub-classification of cirrhosis using collagen proportionate area in patients with chronic hepatitis C

Collagen proportionate area (CPA, %) is used to quantify liver fibrosis. Here, we assessed CPA performance to sub-classify cirrhosis. CPA was measured in explanted livers from consecutively transplanted patients for hepatitis C virus-related cirrhosis. Model for end-stage liver disease (MELD), Child-Pugh score and decompensating events (ascites, variceal bleeding, non-obstructive jaundice and encephalopathy) were recorded at the time of liver transplant. Of the 154 patients, 24%, 12%, 35%, 24% and 5% had zero, one, two, three and four previous decompensating events. Patients with decompensation had significantly higher CPA than those without (25.1 ± 8.4 vs 15.8 ± 5.5, P < .001). Decompensation was independently associated with CPA, bilirubin and albumin or with CPA and MELD score. CPA did not differ between patients with one, two, three or four decompensating events (22.2 ± 6.3 vs 26.6 ± 8.9 vs 24.5 ± 7.7 vs 24.4 ± 10.9, P = .242). Overall, CPA correlates with the clinical severity of cirrhosis until the advent of decompensation but not with subsequent decompensating events.

Regression of liver fibrosis: evidence and challenges

It has been reported that liver fibrosis could be reversed after eliminating liver injuries. This article systematically summarizes the evidence of fibrosis regression based on histology, liver stiffness, and serum biomarkers, and discusses several clinically relevant challenges. Evidence from liver biopsy has been regarded as the gold standard in the assessment of fibrosis regression. Semi-quantitative staging and grading systems are traditionally and routinely used to define regression. Recently, the predominantly regressive, indeterminate, and predominantly progressive score was proposed, based on the regressive features from "hepatic repair complex", to provide additional information regarding the quality of fibrosis. For non-invasive assessment, although liver stiffness and serum biomarkers could be applied to reflect the dynamic changes of liver fibrosis, other confounding factors such as liver inflammation have to be considered. In conclusion, both histology and non-invasive methods can provide evidence regarding fibrosis regression. The predictive value of fibrosis regression in long-term prognosis warrants further investigation.

Evolution of the liver biopsy and its future

Liver biopsies are commonly used to evaluate a wide variety of medical disorders, including neoplasms and post-transplant complications. However, its use is being impacted by improved clinical diagnosis of disorders, and non-invasive methods for evaluating liver tissue and as a result the indications of a liver biopsy have undergone major changes in the last decade. The evolution of highly effective treatments for some of the common indications for liver biopsy in the last decade (e.g., viral hepatitis B and C) has led to a decline in the number of liver biopsies in recent years. At the same time, the emergence of better technologies for histologic evaluation, tissue content analysis and genomics are among the many new and exciting developments in the field that hold great promise for the future and are going to shape the indications for a liver biopsy in the future. Recent advances in slide scanners now allow creation of "digital/virtual" slides that have image of the entire tissue section present in a slide [whole slide imaging (WSI)]. WSI can now be done very rapidly and at very high resolution, allowing its use in routine clinical practice. In addition, a variety of technologies have been developed in recent years that use different light sources and/or microscopes allowing visualization of tissues in a completely different way. One such technique that is applicable to liver specimens combines multiphoton microscopy (MPM) with advanced clearing and fluorescent stains known as Clearing Histology with MultiPhoton Microscopy (CHiMP). Although it has not yet been extensively validated, the technique has the potential to decrease inefficiency, reduce artifacts, and increase data while being readily integrable into clinical workflows. Another technology that can provide rapid and in-depth characterization of thousands of molecules in a tissue sample, including liver tissues, is matrix assisted laser desorption/ionization (MALDI) mass spectrometry. MALDI has already been applied in a clinical research setting with promising diagnostic and prognostic capabilities, as well as being able to elucidate mechanisms of liver diseases that may be targeted for the development of new therapies. The logical next step in huge data sets obtained from such advanced analysis of liver tissues is the application of machine learning (ML) algorithms and application of artificial intelligence (AI), for automated generation of diagnoses and prognoses. This review discusses the evolving role of liver biopsies in clinical practice over the decades, and describes newer technologies that are likely to have a significant impact on how they will be used in the future.

Type IV Collagen 7S Is the Most Accurate Test For Identifying Advanced Fibrosis in NAFLD With Type 2 Diabetes

This study aimed to examine whether the diagnostic accuracy of four noninvasive tests (NITs) for detecting advanced fibrosis in nonalcoholic fatty liver disease (NAFLD) is maintained or is inferior to with or without the presence of type 2 diabetes. Overall, 874 patients with biopsy-proven NAFLD were enrolled. After propensity-score matching by age, sex, and the prevalence of dyslipidemia, 311 patients were enrolled in each group of with or without diabetes. To evaluate the effect of diabetes, we compared the diagnostic accuracy of the fibrosis-4 (FIB-4) index, the NAFLD fibrosis score (NFS), the aspartate aminotransferase to platelet ratio index (APRI), and type IV collagen 7S (COL4-7S) in patients with NAFLD with and without diabetes. The areas under the receiver operating characteristic curve (AUROC) for identifying advanced fibrosis in patients without diabetes were 0.879 for the FIB-4 index, 0.851 for the NFS, 0.862 for the APRI, and 0.883 for COL4-7S. The AUROCs in patients with diabetes were 0.790 for the FIB-4 index, 0.784 for the NFS, 0.771 for the APRI, and 0.872 for COL4-7S. The AUROC of COL4-7S was significantly larger than that of the other NITs in patients with NAFLD with diabetes than in those without diabetes. The optimal high and low cutoff points of COL4-7S were 5.9 ng/mL and 4.8 ng/mL, respectively. At the low cutoff point, the accuracy of COL4-7S was better than that of the other NITs, especially in patients with diabetes. Conclusion: COL4-7S measurement might be the best NIT for identifying advanced fibrosis in NAFLD, especially in NAFLD with diabetes.

Evaluation of liver fibrosis in patients with Wilson's disease

OBJECTIVES

Staging of fibrosis in chronic liver disease is important for prognosis and treatment planning. Liver biopsy is the gold standard in fibrosis assessment; however, new methods for fibrosis and stiffness measurement exist which have not been evaluated in patients with Wilson's disease. To evaluate the accuracy of collagen proportionate area (CPA), transient elastography and shear wave elastography (SWE) in the assessment of liver fibrosis in adult patients with Wilson's disease.

METHODS

In this retrospective study of 60 patients with Wilson's disease, results of percutaneous cutting liver biopsy assessed using the Ishak fibrosis score and CPA were compared with liver stiffness measured with transient elastography and SWE.

RESULTS

CPA correlated with the Ishak score (r = 0.45; P = 0.001) and transient elastography results correlated with SWE measurements (r = 0.80; P = 0.0001). In contrast, transient elastography or SWE did not significantly correlate with the Ishak score or CPA.

CONCLUSION

Collagen content assessment may be useful for estimation of liver fibrosis in patients with Wilson's disease. However, single time-point elastographic liver stiffness measurements have a limited diagnostic value in Wilson's disease.

Microscope-Based Automated Quantification of Liver Fibrosis in Mice Using a Deep Learning Algorithm

In preclinical studies that involve animal models for hepatic fibrosis, accurate quantification of the fibrosis is of utmost importance. The use of digital image analysis based on deep learning artificial intelligence (AI) algorithms can facilitate accurate evaluation of liver fibrosis in these models. In the present study, we compared the quantitative evaluation of collagen proportionate area in the carbon tetrachloride model of liver fibrosis in the mouse by a newly developed AI algorithm to the semiquantitative assessment of liver fibrosis performed by a board-certified toxicologic pathologist. We found an excellent correlation between the 2 methods of assessment, most evident in the higher magnification (×40) as compared to the lower magnification (×10). These findings strengthen the confidence of using digital tools in the toxicologic pathology field as an adjunct to an expert toxicologic pathologist.

Dilatation of lymphatic vessels increases liver stiffness on transient elastography irrespective of fibrosis

AIM

Liver stiffness measured using transient elastography (TE) is affected by tissue viscosity. The role of intrahepatic lymphatic fluid in liver stiffness is unclear. The present study aimed to investigate the effects of lymphatic vessel dilatation on liver stiffness.

METHODS

Patients with chronic liver disease (n = 116) were enrolled from June 2018 to March 2020. All specimens were acquired by laparoscopic liver biopsy. Biopsy samples were stained with D2-40 for lymphatic vessel quantification based on a five-point scale for each specimen. Independent associations of liver stiffness measured by TE, strain elasticity (liver fibrosis index), and controlled attenuation parameter with fibrosis, lymphatic vessels, alanine aminotransferase, bilirubin, and steatosis were evaluated.

RESULTS

Fibrosis, splenic stiffness measurement, and splenic volume were significantly correlated with the area of lymphatic vessels. Fibrosis, lymphatic vessels, and alanine aminotransferase were independent factors significantly associated with liver stiffness measurement (LSM; standardized coefficient [β] = 0.375, P < 0.001; β = 0.342, P < 0.001; and β = 0.359, P < 0.001, respectively). Fibrosis was the only independent factor significantly associated with liver fibrosis index (β = 0.360, P < 0.001), whereas the fat deposit area was the only independent factor significantly associated with controlled attenuation parameter (β = 0.455, P < 0.001). The areas under the receiver operating characteristic curves for diagnosing controlled ascites based on LSM, liver fibrosis index, splenic stiffness measurement, collagen proportionate area, and area of lymphatic vessels were 0.94, 0.66, 0.76, 0.64, and 0.79, respectively.

CONCLUSIONS

Lymphatic vessel dilatation can affect liver stiffness measured using TE. Liver stiffness measurement is a predictive factor for ascites.

Liver Collagen Contents Are Closely Associated with the Severity of Cirrhosis and Posthepatectomy Liver Failure in Patients with Hepatocellular Carcinoma and Child-Pugh Grade A Liver Function

BACKGROUND

Hepatocellular carcinoma (HCC) is usually accompanied by different severities of cirrhosis, which is a risk factor for posthepatectomy liver failure (PHLF). Collagen proportional area (CPA) measurements can quantitatively determine the collagen contents of liver tissue. This study explored the impact of CPA on PHLF, and further investigated the correlation between CPA and a non-invasive method, namely cirrhotic severity scoring (CSS), previously proposed by our team.

METHODS

A total of 224 HCC patients with Child-Pugh grade A liver function undergoing hepatectomy between 2017 and 2019 were retrospectively studied. Quantitative digital image analysis of resected liver tissues was used for the CPA measurement. Risk factors for PHLF were subjected to univariate and multivariate analyses, and the correlation between CPA and CSS was analyzed.

RESULTS

Overall, 28 (12.5%) patients experienced PHLF. Patients with PHLF had higher CPA values than those without PHLF (p < 0.001). Multivariate analysis showed CPA and extent of hepatectomy to be independent risk factors for PHLF. CPA values were divided into four stages based on their quartiles (C1: < 6.6%; C2: 6.6-10.7%; C3: 10.7-18.0%; C4: ≥ 18.0%). The incidence of PHLF increased with increasing CPA stages (p < 0.001). Furthermore, CSS was significantly correlated with CPA (r = 0.720; p < 0.001). The incidence of PHLF also increased with increasing severity of cirrhosis evaluated by CSS (p < 0.001).

CONCLUSIONS

In HCC patients with Child-Pugh grade A liver function, cirrhosis could be staged by liver collagen contents, which significantly influenced PHLF. Furthermore, CSS was useful in the preoperative evaluation of cirrhotic severity.

Noninvasive diagnosis of portal hypertension using gadoxetate DCE-MRI of the liver and spleen

OBJECTIVES

To assess the performance of gadoxetate dynamic contrast-enhanced (DCE) MRI of the liver and spleen for noninvasive diagnosis of portal hypertension (PH).

METHODS

Thirty-five patients (M/F 22/13, mean age 55 years) with chronic liver disease who underwent hepatic venous pressure gradient (HVPG) measurements were prospectively enrolled in this IRB-approved study. All patients underwent multiparametric MRI including gadoxetate DCE-MRI acquisition. Model-based and model-free DCE-MRI analyses were performed. The correlation between DCE-MRI parameters and HVPG was assessed. ROC analysis was employed to determine the diagnostic performance of DCE-MRI parameters alone and in combination for prediction of PH and clinically significant (CS)PH (HVPG > 5 and ≥ 10 mmHg, respectively).

RESULTS

Mean HVPG was 7.0 ± 5.0 mmHg (range 0-18 mmHg). Twenty-one (60%) patients had PH, of whom 9 had CSPH. Modeled liver uptake fraction f_i and uptake rate k_i and model-free parameters liver upslope and uptake were all significantly negatively correlated with HVPG (r range - 0.490 to - 0.398, p value range 0.003-0.018), while spleen interstitial fraction v_e was significantly positively correlated with HVPG (r = 0.336, p = 0.048). For PH diagnosis, liver k_i showed the best diagnostic performance with an AUC, sensitivity, and specificity of 0.74 (confidence interval (CI) 0.57-0.91), 71.4%, and 78.6%. The combination of liver k_i and spleen v_e was selected as the best classifier for diagnosis of CSPH with an AUC, sensitivity, and specificity of 0.87 (CI 0.75-0.99), 100%, and 73.1%.

CONCLUSIONS

Our results demonstrate the potential utility of hepatocyte uptake parameters and spleen interstitial fraction obtained with gadoxetate DCE-MRI for the diagnosis of PH and CSPH.

KEY POINTS

• Liver uptake and spleen interstitial fraction estimates from gadoxetate DCE-MRI are significantly correlated with portal pressure measurements. • Liver uptake rate shows good diagnostic performance for the diagnosis of portal hypertension. • The combination of liver uptake rate with spleen interstitial fraction exhibits excellent diagnostic performance for the diagnosis of clinically significant portal hypertension.

Digital pathology: accurate technique for quantitative assessment of histological features in metabolic-associated fatty liver disease

BACKGROUND

Histological evaluation of metabolic-associated fatty liver disease (MAFLD) biopsies is subjective, descriptive and with interobserver variability.

AIMS

To examine the relationship between different histological features (fibrosis, steatosis, inflammation and iron) measured with automated whole-slide quantitative digital pathology and corresponding semiquantitative scoring systems, and the distribution of digital pathology measurements across Fatty Liver Inhibition of Progression (FLIP) algorithm and Steatosis, Activity and Fibrosis (SAF) scoring system METHODS: We prospectively included 136 consecutive patients who underwent liver biopsy for MAFLD at three Spanish centres (January 2017-January 2020). Biopsies were scored by two blinded pathologists according to the Non-alcoholic Steatohepatitis (NASH) Clinical Research Network system for fibrosis staging, the FLIP/SAF classification for steatosis and inflammation grading and Deugnier score for iron grading. Proportionate areas of collagen, fat, inflammatory cells and iron deposits were measured with computer-assisted digital image analysis. A test-retest experiment was performed for precision repeatability evaluation.

RESULTS

Digital pathology showed strong correlation with fibrosis (r = 0.79; P < 0.001), steatosis (r = 0.85; P < 0.001) and iron (r = 0.70; P < 0.001). Performance was lower when assessing the degree of inflammation (r = 0.35; P < 0.001). NASH cases had a higher proportion of collagen and fat compared to non-NASH cases (P < 0.005), whereas inflammation and iron quantification did not show significant differences between categories. Repeatability evaluation showed that all the coefficients of variation were ≤1.1% and all intraclass correlation coefficient values were ≥0.99, except those of collagen.

CONCLUSION

Digital pathology allows an automated, precise, objective and quantitative assessment of MAFLD histological features. Digital analysis measurements show good concordance with pathologists´ scores.

Liver biopsy in the quantitative assessment of liver fibrosis in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) is a major cause of liver fibrosis/cirrhosis and liver-related mortality. Despite emergence of noninvasive tests, liver biopsy remains the mainstay for the diagnosis and assessment of disease severity and chronicity. Accurate detection and quantification of liver fibrosis with architectural localization are essential for assessing the severity of NAFLD and its response to antifibrotic therapy in clinical trials. Conventional histological scoring systems for liver fibrosis are semiquantitative. Collagen proportionate area is morphometric by measuring the percentage of fibrosis on a continuous scale but is limited by the absence of architectural input. Ultra-fast laser microscopy, e.g., second harmonic generation (SHG) imaging, has enabled in-depth analysis of fibrillary collagen based on intrinsic optical signals. Quantification and calculation of different detailed variables of collagen fibers can be used to establish algorithm-based quantitative fibrosis scores (e.g. qFibrosis, q-FPs) in NAFLD. Artificial intelligence is being explored to further develop quantitative fibrosis scoring methods. SHG microscopy should be considered the new gold standard for the quantitative assessment of liver fibrosis, reaffirming the pivotal role of the liver biopsy in NAFLD, at least for the near-future. The ability of SHG-derived algorithms to intuitively detect subtle nuances in liver fibrosis changes over a continuous scale should be employed to redress the efficacy endpoint for fibrosis in NASH clinical trials. The current decrease by 1-point or more in fibrosis stage may not be realistic for the evaluation of therapeutic response to antifibrotic drugs in relatively short-term trials.