Quantitative magnetic resonance imaging in patients with cirrhosis: a cross-sectional study

Construction of a prediction model for hepatic encephalopathy in acute-on-chronic liver failure patients

OBJECTIVE

Hepatic encephalopathy (HE) is a serious complication of acute-on-chronic liver failure (ACLF) that requires early detection and intervention to positively impact patient prognosis. This study aimed to develop a reliable model to predict HE in ACLF patients during hospitalization.

METHODS

Retrospectively recruiting 255 hepatitis B-related ACLF patients, including 67 who developed HE during hospitalization, the study analysed clinical data and biochemical indices collected during the first week of admission. The least absolute shrinkage and selection operator (LASSO) was used to identify characteristic predictors for hospitalization HE events, and a logistic regression model was subsequently developed. Receiver operating characteristic (ROC) curves, calibration curves, and bootstrap resampling were used to evaluate the model's discrimination, consistency, and accuracy, and a nomogram was created to visualize the model. An external validation cohort of 236 liver failure patients collected from the same medical centre between 2007 and 2010 was used to validate the model.

RESULTS

The study found that blood urea nitrogen (BUN), alpha-fetoprotein (AFP), international normalized ratio (INR), serum ammonia, and infection complications during hospitalization were risk factors for HE in ACLF patients. The new model predicted the development of HE in ACLF patients with an area under the receiver operating characteristic curve (AUROC) of 85.2%, which was superior to other models. The best threshold for the new model was 0.28, resulting in a specificity of 81.4% and a sensitivity of 80.6%. In the validation group, the new model showed similar results, with an AUROC of 79% and a specificity of 83.6% and a sensitivity of 56.6%.

CONCLUSION

This study developed and validated a new prediction model for HE in ACLF patients offering a useful tool for early identification of patients with a high risk of HE in clinical settings. However, to ascertain the model's general effectiveness, future prospective multicentre studies are warranted.

White matter microstructural disruption in minimal hepatic encephalopathy: a neurite orientation dispersion and density imaging (NODDI) study

PURPOSE

To evaluate the ability of neurite orientation dispersion and density imaging (NODDI) for detecting white matter (WM) microstructural abnormalities in minimal hepatic encephalopathy (MHE).

METHODS

Diffusion-weighted images, enabling the estimation of NODDI and diffusion tensor imaging (DTI) parameters, were acquired from 20 healthy controls (HC), 22 cirrhotic patients without MHE (NHE), and 15 cirrhotic patients with MHE. Tract-based spatial statistics were used to determine differences in DTI (including fractional anisotropy [FA] and mean/axial/radial diffusivity [MD/AD/RD]) and NODDI parameters (including neurite density index [NDI], orientation dispersion index [ODI], and isotropic volume fraction [ISO]). Voxel-wise analyses of correlations between diffusion parameters and neurocognitive performance determined by Psychometric Hepatic Encephalopathy Score (PHES) were completed.

RESULTS

MHE patients had extensive NDI reduction and rare ODI reduction, primarily involving the genu and body of corpus callosum and the bilateral frontal lobe, corona radiata, external capsule, anterior limb of internal capsule, temporal lobe, posterior thalamic radiation, and brainstem. The extent of NDI and ODI reduction expanded from NHE to MHE. In both MHE and NHE groups, the extent of NDI change was quite larger than that of FA change. No significant intergroup difference in ISO/MD/AD/RD was observed. Tissue specificity afforded by NODDI revealed the underpinning of FA reduction in MHE. The NDI in left frontal lobe was significantly correlated with PHES.

CONCLUSION

MHE is characterized by diffuse WM microstructural impairment (especially neurite density reduction). NODDI can improve the detection of WM microstructural impairments in MHE and provides more precise information about MHE-related pathology than DTI.

Quantitative chemical exchange saturation transfer imaging of nuclear overhauser effects in acute ischemic stroke

PURPOSE

In chemical exchange saturation transfer imaging, saturation effects between - 2 to - 5 ppm (nuclear Overhauser effects, NOEs) have been shown to exhibit contrast in preclinical stroke models. Our previous work on NOEs in human stroke used an analysis model that combined NOEs and semisolid MT; however their combination might feasibly have reduced sensitivity to changes in NOEs. The aim of this study was to explore the information a 4-pool Bloch-McConnell model provides about the NOE contribution in ischemic stroke, contrasting that with an intentionally approximate 3-pool model.

METHODS

MRI data from 12 patients presenting with ischemic stroke were retrospectively analyzed, as well as from six animals induced with an ischemic lesion. Two Bloch-McConnell models (4 pools, and a 3-pool approximation) were compared for their ability to distinguish pathological tissue in acute stroke. The association of NOEs with pH was also explored, using pH phantoms that mimic the intracellular environment of naïve mouse brain.

RESULTS

The 4-pool measure of NOEs exhibited a different association with tissue outcome compared to 3-pool approximation in the ischemic core and in tissue that underwent delayed infarction. In the ischemic core, the 4-pool measure was elevated in patient white matter ( 1 . 20 ± 0 . 20 ) and in animals ( 1 . 27 ± 0 . 20 ). In the naïve brain pH phantoms, significant positive correlation between the NOE and pH was observed.

CONCLUSION

Associations of NOEs with tissue pathology were found using the 4-pool metric that were not observed using the 3-pool approximation. The 4-pool model more adequately captured in vivo changes in NOEs and revealed trends depending on tissue pathology in stroke.

Hepatic encephalopathy: Novel insights into classification, pathophysiology and therapy

Hepatic encephalopathy (HE) is a frequent and serious complication of both chronic liver disease and acute liver failure. HE manifests as a wide spectrum of neuropsychiatric abnormalities, from subclinical changes (mild cognitive impairment) to marked disorientation, confusion and coma. The clinical and economic burden of HE is considerable, and it contributes greatly to impaired quality of life, morbidity and mortality. This review will critically discuss the latest classification of HE, as well as the pathogenesis and pathophysiological pathways underlying the neurological decline in patients with end-stage liver disease. In addition, management strategies, diagnostic approaches, currently available therapeutic options and novel treatment strategies are discussed.

Analysis of Risk Factors for Postoperative Delirium After Liver Transplantation

PURPOSE

The study aimed to analyze the incidence of postoperative delirium (POD) and associated risk factors after liver transplantation (LT).

PATIENTS AND METHODS

We identified and enrolled patients undergoing LT at the Second Xiangya Hospital, Central South University between August 2018 and May 2019. We abstracted their relevant clinical information and assigned the patients into a POD group and non-POD group to compare differences in clinical information. Risk factors of POD were analyzed using logistic regression.

RESULTS

A total of 159 LT patients were enrolled. Forty-two patients exhibited delirium (26.4%). Of the 42 with delirium, 33 (78.6%) had delirium within 3 days postoperatively and a median duration of 5 days (quartile 3-7 days). The results of binary logistic regression are as follows: preoperative ammonia (≥46 vs <46 μmol/L; OR 3.51, 95% CI [1.31-9.46], P<0.05), Model for End-Stage Liver Disease (MELD) score (≥15 vs.<15; OR 3.33, 95% CI [1.27-8.79], P<0.05), presence of hepatic encephalopathy (OR 3.30, 95% CI [1.20-9.07], P<0.05), aspartate aminotransferase (AST) on day 1 postoperatively (OR 1.33, 95% CI [1.06 -1.68], P<0.05), anhepatic period (OR 1.04, 95% CI [1.02 -1.06], P<0.01). The POD group had a longer intubation time (2925.0 vs 1410.0 min, P<0.01), ICU length of stay (6 vs 4 d, P<0.01) and increased medical costs (43.96 vs 33.74 ten thousand yuan, P<0.01).

CONCLUSION

The incidence of POD in LT patients is a significant clinical feature. Ammonia ≥46 μmol/l, MELD score ≥15, hepatic encephalopathy, anhepatic period, and AST at 1 day postoperatively were independent risk factors for POD.

Brain Edema in Chronic Hepatic Encephalopathy

Brain edema is a common feature associated with hepatic encephalopathy (HE). In patients with acute HE, brain edema has been shown to play a crucial role in the associated neurological deterioration. In chronic HE, advanced magnetic resonance imaging (MRI) techniques have demonstrated that low-grade brain edema appears also to be an important pathological feature. This review explores the different methods used to measure brain edema ex vivo and in vivo in animal models and in humans with chronic HE. In addition, an in-depth description of the main studies performed to date is provided. The role of brain edema in the neurological alterations linked to HE and whether HE and brain edema are the manifestations of the same pathophysiological mechanism or two different cerebral manifestations of brain dysfunction in liver disease are still under debate. In vivo MRI/magnetic resonance spectroscopy studies have allowed insight into the development of brain edema in chronic HE. However, additional in vivo longitudinal and multiparametric/multimodal studies are required (in humans and animal models) to elucidate the relationship between liver function, brain metabolic changes, cellular changes, cell swelling, and neurological manifestations in chronic HE.

Multimodal MR imaging in hepatic encephalopathy: state of the art

Hepatic encephalopathy (HE) is a neurological or neuropsychological complication due to liver failure or portosystemic shunting. The clinical manifestation is highly variable, which can exhibit mild cognitive or motor impairment initially, or gradually progress to a coma, even death, without treatment. Neuroimaging plays a critical role in uncovering the neural mechanism of HE. In particular, multimodality MR imaging is able to assess both structural and functional derangements of the brain with HE in focal or neural network perspectives. In recent years, there has been rapid development in novel MR technologies and applications to investigate the pathophysiological mechanism of HE. Therefore, it is necessary to update the latest MR findings regarding HE by use of multimodality MRI to refine and deepen our understanding of the neural traits in HE. Herein, this review highlights the latest MR imaging findings in HE to refresh our understanding of MRI application in HE.

Hepatic encephalopathy: current challenges and future prospects

Hepatic encephalopathy (HE) is a common complication of liver dysfunction, including acute liver failure and liver cirrhosis. HE presents as a spectrum of neuropsychiatric symptoms ranging from subtle fluctuating cognitive impairment to coma. It is a significant contributor of morbidity in patients with liver disease. HE is observed in acute liver failure, liver bypass procedures, for example, shunt surgry and transjugular intrahepatic portosystemic shunt, and cirrhosis. These are classified as Type A, B and C HE, respectively. HE can also be classified according to whether its presence is overt or covert. The pathogenesis is linked with ammonia and glutamine production, and treatment is based on mechanisms to reduce the formation and/or removal of these compounds. There is no specific diagnostic test for HE, and diagnosis is based on clinical suspicion, excluding other causes and use of clinical tests that may support its diagnosis. Many tests are used in trials and experimentally, but have not yet gained universal acceptance. This review focuses on the definitions, pathogenesis and treatment of HE. Consideration will be given to existing treatment, including avoidance of precipitating factors and novel therapies such as prebiotics, probiotics, antibiotics, laxatives, branched-chain amino acids, shunt embolization and the importance of considering liver transplant in appropriate cases.

Early primary biliary cholangitis is characterised by brain abnormalities on cerebral magnetic resonance imaging

BACKGROUND

Brain change can occur in primary biliary cholangitis (PBC), potentially as a result of cholestatic and/or inflammatory processes. This change is linked to systemic symptoms of fatigue and cognitive impairment.

AIM

To identify whether brain change occurs early in PBC. If the change develops early and is progressive, it may explain the difficulty in treating these symptoms.

METHODS

Early disease brain change was explored in 13 patients with newly diagnosed biopsy-proven precirrhotic PBC using magnetisation transfer, diffusion-weighted imaging and ¹ H magnetic resonance spectroscopy. Results were compared to 17 healthy volunteers.

RESULTS

Cerebral magnetisation transfer ratios were reduced in early PBC, compared to healthy volunteers, in the thalamus, putamen and head of caudate with no greater reduction in patients with greater symptom severity. Mean apparent diffusion coefficients were increased in the thalamus only. No ¹ H magnetic resonance spectroscopy abnormalities were seen. Serum manganese levels were elevated in all PBC patients, but no relationship was seen with imaging or symptom parameters. There were no correlations between neuroimaging data, laboratory data, symptom severity scores or age.

CONCLUSIONS

This is the first study to be performed in this precirrhotic patient population, and we have highlighted that neuroimaging changes are present at a much earlier stage than previously demonstrated. The neuroimaging abnormalities suggest that the brain changes seen in PBC occur early in the pathological process, even before significant liver damage has occurred. If such changes are linked to symptom pathogenesis, this could have important implications for the timing of second-line-therapy use.