A change in biophysical properties accompanies heterochromatin formation in mouse embryos.

The majority of our genome is composed of repeated DNA sequences that assemble into heterochromatin, a highly compacted structure that constrains their mutational potential. How heterochromatin forms during development and how its structure is maintained are not fully understood. Here, we show that mouse heterochromatin phase-separates after fertilization, during the earliest stages of mammalian embryogenesis. Using high-resolution quantitative imaging and molecular biology approaches, we show that pericentromeric heterochromatin displays properties consistent with a liquid-like state at the two-cell stage, which change at the four-cell stage, when chromocenters mature and heterochromatin becomes silent. Disrupting the condensates results in altered transcript levels of pericentromeric heterochromatin, suggesting a functional role for phase separation in heterochromatin function. Thus, our work shows that mouse heterochromatin forms membrane-less compartments with biophysical properties that change during development and provides new insights into the self-organization of chromatin domains during mammalian embryogenesis.

NudC guides client transfer between the Hsp40/70 and Hsp90 chaperone systems.

In the eukaryotic cytosol, the Hsp70 and the Hsp90 chaperone machines work in tandem with the maturation of a diverse array of client proteins. The transfer of nonnative clients between these systems is essential to the chaperoning process, but how it is regulated is still not clear. We discovered that NudC is an essential transfer factor with an unprecedented mode of action: NudC interacts with Hsp40 in Hsp40-Hsp70-client complexes and displaces Hsp70. Then, the interaction of NudC with Hsp90 allows the direct transfer of Hsp40-bound clients to Hsp90 for further processing. Consistent with this mechanism, NudC increases client activation in vitro as well as in cells and is essential for cellular viability. Together, our results show the complexity of the cooperation between the major chaperone machineries in the eukaryotic cytosol.

Lake heatwaves under climate change.

Lake ecosystems, and the organisms that live within them, are vulnerable to temperature change1-5, including the increased occurrence of thermal extremes6. However, very little is known about lake heatwaves-periods of extreme warm lake surface water temperature-and how they may change under global warming. Here we use satellite observations and a numerical model to investigate changes in lake heatwaves for hundreds of lakes worldwide from 1901 to 2099. We show that lake heatwaves will become hotter and longer by the end of the twenty-first century. For the high-greenhouse-gas-emission scenario (Representative Concentration Pathway (RCP) 8.5), the average intensity of lake heatwaves, defined relative to the historical period (1970 to 1999), will increase from 3.7 ± 0.1 to 5.4 ± 0.8 degrees Celsius and their average duration will increase dramatically from 7.7 ± 0.4 to 95.5 ± 35.3 days. In the low-greenhouse-gas-emission RCP 2.6 scenario, heatwave intensity and duration will increase to 4.0 ± 0.2 degrees Celsius and 27.0 ± 7.6 days, respectively. Surface heatwaves are longer-lasting but less intense in deeper lakes (up to 60 metres deep) than in shallower lakes during both historic and future periods. As lakes warm during the twenty-first century7,8, their heatwaves will begin to extend across multiple seasons, with some lakes reaching a permanent heatwave state. Lake heatwaves are likely to exacerbate the adverse effects of long-term warming in lakes and exert widespread influence on their physical structure and chemical properties. Lake heatwaves could alter species composition by pushing aquatic species and ecosystems to the limits of their resilience. This in turn could threaten lake biodiversity9 and the key ecological and economic benefits that lakes provide to society.

Coordinated Conformational Processing of the Tumor Suppressor Protein p53 by the Hsp70 and Hsp90 Chaperone Machineries.

p53, the guardian of the genome, requires chaperoning by Hsp70 and Hsp90. However, how the two chaperone machineries affect p53 conformation and regulate its function remains elusive. We found that Hsp70, together with Hsp40, unfolds p53 in an ATP-dependent reaction. This unfolded state of p53 is susceptible to aggregation after release induced by the nucleotide exchange factor Bag-1. However, when Hsp90 and the adaptor protein Hop are present, p53 is transferred from Hsp70 to Hsp90, allowing restoration of the native state upon ATP hydrolysis. Our results suggest that the p53 conformation is constantly remodeled by the two major chaperone machineries. This connects p53 activity to stress, and the levels of free molecular chaperones are important factors regulating p53 activity. Together, our findings reveal an intricate interplay and cooperation of Hsp70 and Hsp90 in regulating the conformation of a client.

Reliability and accuracy of single-molecule FRET studies for characterization of structural dynamics and distances in proteins.

Single-molecule Förster-resonance energy transfer (smFRET) experiments allow the study of biomolecular structure and dynamics in vitro and in vivo. We performed an international blind study involving 19 laboratories to assess the uncertainty of FRET experiments for proteins with respect to the measured FRET efficiency histograms, determination of distances, and the detection and quantification of structural dynamics. Using two protein systems with distinct conformational changes and dynamics, we obtained an uncertainty of the FRET efficiency ≤0.06, corresponding to an interdye distance precision of ≤2 Å and accuracy of ≤5 Å. We further discuss the limits for detecting fluctuations in this distance range and how to identify dye perturbations. Our work demonstrates the ability of smFRET experiments to simultaneously measure distances and avoid the averaging of conformational dynamics for realistic protein systems, highlighting its importance in the expanding toolbox of integrative structural biology.

Shrinking gate fluorescence correlation spectroscopy yields equilibrium constants and separates photophysics from structural dynamics.

Fluorescence correlation spectroscopy is a versatile tool for studying fast conformational changes of biomolecules especially when combined with Förster resonance energy transfer (FRET). Despite the many methods available for identifying structural dynamics in FRET experiments, the determination of the forward and backward transition rate constants and thereby also the equilibrium constant is difficult when two intensity levels are involved. Here, we combine intensity correlation analysis with fluorescence lifetime information by including only a subset of photons in the autocorrelation analysis based on their arrival time with respect to the excitation pulse (microtime). By fitting the correlation amplitude as a function of microtime gate, the transition rate constants from two fluorescence-intensity level systems and the corresponding equilibrium constants are obtained. This shrinking-gate fluorescence correlation spectroscopy (sg-FCS) approach is demonstrated using simulations and with a DNA origami-based model system in experiments on immobilized and freely diffusing molecules. We further show that sg-FCS can distinguish photophysics from dynamic intensity changes even if a dark quencher, in this case graphene, is involved. Finally, we unravel the mechanism of a FRET-based membrane charge sensor indicating the broad potential of the method. With sg-FCS, we present an algorithm that does not require prior knowledge and is therefore easily implemented when an autocorrelation analysis is carried out on time-correlated single-photon data.

Paxillin regulates liver fibrosis via actin polymerization and ERK activation in hepatic stellate cells.

Liver injury leads to fibrosis and cirrhosis. The primary mechanism underlying the fibrogenic response is the activation of hepatic stellate cells (HSCs), which are 'quiescent' in normal liver but become 'activated' after injury by transdifferentiating into extracellular matrix (ECM)-secreting myofibroblasts. Given that integrins are important in HSC activation and fibrogenesis, we hypothesized that paxillin, a key downstream effector in integrin signaling, might be critical in the fibrosis pathway. Using a cell-culture-based model of HSC activation and in vivo models of liver injury, we found that paxillin is upregulated in activated HSCs and fibrotic livers. Overexpression of paxillin (both in vitro and in vivo) led to increased ECM protein expression, and depletion of paxillin in a novel conditional mouse injury model reduced fibrosis. The mechanism by which paxillin mediated this effect appeared to be through the actin cytoskeleton, which signals to the ERK pathway and induces ECM protein production. These data highlight a novel role for paxillin in HSC biology and fibrosis.

Non-invasive liver disease assessment to identify portal hypertension: A systematic review supporting the AASLD Practice Guideline.

INTRODUCTION: Portal hypertension is a serious complication of cirrhosis, which leads to life-threatening complications. Hepatic venous pressure gradient (HVPG), a surrogate of portal pressure, is the reference standard test to assess the severity of portal hypertension. However, since HVPG is limited by its invasiveness and by its availability, non-invasive liver disease assessments (NILDAs) to assess portal pressure, especially clinically significant portal hypertension (CSPH), are needed. METHODS: We conducted a systematic review of Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations, and Daily, Ovid EMBASE, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus from each database's inception to April 22 nd , 2022. We included only studies in English that examined ≥50 patients in single liver disease etiologies which compared non-invasive tests (blood, and/or imaging) to HVPG for predicting clinically significant portal hypertension (CSPH; defined as HVPG ≥10 mm Hg) in patients with chronic liver disease (this therefore limited the number of studies that could be included). Outcomes reported included measures of diagnostic test accuracy. Additionally, a narrative review of studies not eligible for the systematic review is also provided. RESULTS: Nine studies with 2,492 patients met the inclusion criteria. There was substantial heterogeneity with regard to liver disease studied and cutoff values used to detect CSPH. Blood based tests, including aspartate to platelet ratio index (APRI) (56% sensitivity and 68% specificity) and fibrosis-4 (FIB-4) (54% sensitivity and 73% specificity) had low accuracy measures. Imaging based tests (transient elastography (TE) and shear wave elastography detection of liver stiffness (LSM)) had better accuracy, but also had substantial variation; at 15 kPa, TE sensitivity was 90%-96% and specificity was 48%-50% while at 25 kPa, its sensitivity and specificity were 57%-85% and 82%-93%, respectively. The narrative review suggested that imaging based tests are the best available NILDA to detect CSPH, CSPH is highly unlikely to be present at an LSM ≤15 kPa and likely to be present at an LSM ≥25 kPa. CONCLUSION: While imaging-based NILDA appeared to have higher accuracy than blood-based tests to detect CSPH, only 9 studies fit the a priori established inclusion criteria for the SR. In addition, there was substantial study heterogeneity and variation in cutoffs for LSM to detect CSPH, limiting the ability to establish definitive cutoffs to detect CSPH.

Imaging-based non-invasive liver disease assessment for staging liver fibrosis in chronic liver disease: A systematic review supporting the AASLD Practice Guideline.

BACKGROUND AND AIMS: Transient elastography (TE), shear-wave elastography (SWE), and/or magnetic resonance elastography (MRE), each providing liver stiffness measurement (LSM), are the most studied imaging-based noninvasive liver disease assessment (NILDA) techniques. To support the American Association for the Study of Liver Diseases guidelines on NILDA, we summarized the evidence on the accuracy of these LSM methods to stage liver fibrosis (F). APPROACH AND RESULTS: A comprehensive search for studies assessing LSM by TE, SWE, or MRE for the identification of significant fibrosis (F2-4), advanced fibrosis (F3-4), or cirrhosis (F4), utilizing histopathology as standard of reference by liver disease etiology in adults or children from inception to April 2022 was performed. We excluded studies with <50 patients with a single disease entity and mixed liver disease etiologies (with the exception of HCV/HIV co-infection). Out of 9447 studies, 240 with 61,193 patients were included in this systematic review. In adults, sensitivities for the identification of F2-4 ranged from 51% to 95%, for F3-4 from 70% to 100%, and for F4 from 60% to 100% across all techniques/diseases, whereas specificities ranged from 36% to 100%, 74% to 100%, and 67% to 99%, respectively. The largest body of evidence available was for TE; MRE appeared to be the most accurate method. Imaging-based NILDA outperformed blood-based NILDA in most comparisons, particularly for the identification of F3-4/F4. In the pediatric population, imaging-based NILDA is likely as accurate as in adults. CONCLUSION: LSM from TE, SWE, and MRE show acceptable to outstanding accuracy for the detection of liver fibrosis across various liver disease etiologies. Accuracy increased from F2-4 to F3-4 and was the highest for F4. Further research is needed to better standardize the use of imaging-based NILDA, particularly in pediatric liver diseases.

Accuracy of blood-based biomarkers for staging liver fibrosis in chronic liver disease: A systematic review supporting the AASLD Practice Guideline.

BACKGROUND AND AIMS: Blood-based biomarkers have been proposed as an alternative to liver biopsy for non-invasive liver disease assessment (NILDA) in chronic liver disease (CLD). Our aims for this systematic review were to evaluate the diagnostic utility of selected blood-based tests either alone, or in combination, for identifying significant fibrosis (F2-4), advanced fibrosis (F3-4) and cirrhosis (F4), as compared to biopsy in CLD. APPROACH AND RESULTS: We included a comprehensive search of databases including Ovid MEDLINE(R), EMBASE, Cochrane Database, and Scopus through to April 2022. Two independent reviewers selected 286 studies with 103,162 patients. The most frequently identified studies included the simple aminotransferase-to-platelet ratio index (APRI) and fibrosis (FIB)-4 markers (with low-to-moderate risk of bias) in hepatitis B virus (HBV) and C virus (HCV), HIV-HCV/HBV co-infection, and nonalcoholic fatty liver disease (NAFLD). Positive (LR+) and negative (LR) likelihood ratios across direct and indirect biomarker tests for HCV and HBV for F2-4, F3-4, or F4 were 1.66-6.25 and 0.23-0.80, 1.89-5.24 and 0.12-0.64, and 1.32-7.15 and 0.15-0.86 respectively; LR+ and LR for NAFLD F2-4, F3-4 and F4 were 2-65-3.37 and 0.37-0.39, 2.25-6.76 and 0.07-0.87, and 3.90 and 0.15 respectively. Overall, proportional odds ratio indicated FIB-4 <1.45 was better than APRI <0.5 for F2-4. FIB-4 >3.25 was also better than APRI >1.5 for F3-4 and F4. There was limited data for combined tests. CONCLUSIONS: Blood-based biomarkers are associated with small-to-moderate change in pre-test probability for diagnosing F2-4, F3-4, and F4 in viral hepatitis, HIV-HCV co-infection, and NAFLD, with limited comparative or combination studies for other CLD.

Chaperonin-catalyzed rescue of kinetically trapped states in protein folding.

GroEL and GroES form a chaperonin nano-cage for single protein molecules to fold in isolation. The folding properties that render a protein chaperonin dependent are not yet understood. Here, we address this question using a double mutant of the maltose-binding protein DM-MBP as a substrate. Upon spontaneous refolding, DM-MBP populates a kinetically trapped intermediate that is collapsed but structurally disordered. Introducing two long-range disulfide bonds into DM-MBP reduces the entropic folding barrier of this intermediate and strongly accelerates native state formation. Strikingly, steric confinement of the protein in the chaperonin cage mimics the kinetic effect of constraining disulfides on folding, in a manner mediated by negative charge clusters in the cage wall. These findings suggest that chaperonin dependence correlates with the tendency of proteins to populate entropically stabilized folding intermediates. The capacity to rescue proteins from such folding traps may explain the uniquely essential role of chaperonin cages within the cellular chaperone network.

North American tree migration paced by climate in the West, lagging in the East.

Tree fecundity and recruitment have not yet been quantified at scales needed to anticipate biogeographic shifts in response to climate change. By separating their responses, this study shows coherence across species and communities, offering the strongest support to date that migration is in progress with regional limitations on rates. The southeastern continent emerges as a fecundity hotspot, but it is situated south of population centers where high seed production could contribute to poleward population spread. By contrast, seedling success is highest in the West and North, serving to partially offset limited seed production near poleward frontiers. The evidence of fecundity and recruitment control on tree migration can inform conservation planning for the expected long-term disequilibrium between climate and forest distribution.

Deep-LASI, single-molecule data analysis software.

By avoiding ensemble averaging, single-molecule methods provide novel means of extracting mechanistic insights into function of material and molecules at the nanoscale. However, one of the big limitations is the vast amount of data required for analyzing and extracting the desired information, which is time-consuming and user dependent. Here, we introduce Deep-LASI, a software suite for the manual and automatic analysis of single-molecule traces, interactions, and the underlying kinetics. The software can handle data from one-, two- and three-color fluorescence data, and was particularly designed for the analysis of two- and three-color single-molecule fluorescence resonance energy transfer experiments. The functionalities of the software include: the registration of multiple-channels, trace sorting and categorization, determination of the photobleaching steps, calculation of fluorescence resonance energy transfer correction factors, and kinetic analyses based on hidden Markov modeling or deep neural networks. After a kinetic analysis, the ensuing transition density plots are generated, which can be used for further quantification of the kinetic parameters of the system. Each step in the workflow can be performed manually or with the support of machine learning algorithms. Upon reading in the initial data set, it is also possible to perform the remaining analysis steps automatically without additional supervision. Hence, the time dedicated to the analysis of single-molecule experiments can be reduced from days/weeks to minutes. After a thorough description of the functionalities of the software, we also demonstrate the capabilities of the software via the analysis of a previously published dynamic three-color DNA origami structure fluctuating between three states. With the drastic time reduction in data analysis, new types of experiments become realistically possible that complement our currently available palette of methodologies for investigating the nanoworld.

AGA Clinical Practice Update on Management of Iron Deficiency Anemia: Expert Review.

DESCRIPTION: In this Clinical Practice Update (CPU), we will Best Practice Advice (BPA) guidance on the appropriate management of iron deficiency anemia. METHODS: This expert review was commissioned and approved by the AGA Institute Clinical Practice Updates Committee (CPUC) and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership, and underwent internal peer review by the CPUC and external peer review through standard procedures of Clinical Gastroenterology and Hepatology. These Best Practice Advice (BPA) statements were drawn from a review of the published literature and from expert opinion. Since systematic reviews were not performed, these BPA statements do not carry formal ratings regarding the quality of evidence or strength of the presented considerations. BEST PRACTICE ADVICE 1: No single formulation of oral iron has any advantages over any other. Ferrous sulfate is preferred as the least expensive iron formulation. BEST PRACTICE ADVICE 2: Give oral iron once a day at most. Every-other-day iron dosing may be better tolerated for some patients with similar or equal rates of iron absorption as daily dosing. BEST PRACTICE ADVICE 3: Add vitamin C to oral iron supplementation to improve absorption. BEST PRACTICE ADVICE 4: Intravenous iron should be used if the patient does not tolerate oral iron, ferritin levels do not improve with a trial of oral iron, or the patient has a condition in which oral iron is not likely to be absorbed. BEST PRACTICE ADVICE 5: Intravenous iron formulations that can replace iron deficits with 1 or 2 infusions are preferred over those that require more than 2 infusions. BEST PRACTICE ADVICE 6: All intravenous iron formulations have similar risks; true anaphylaxis is very rare. The vast majority of reactions to intravenous iron are complement activation-related pseudo-allergy (infusion reactions) and should be treated as such. BEST PRACTICE ADVICE 7: Intravenous iron therapy should be used in individuals who have undergone bariatric procedures, particularly those that are likely to disrupt normal duodenal iron absorption, and have iron-deficiency anemia with no identifiable source of chronic gastrointestinal blood loss. BEST PRACTICE ADVICE 8: In individuals with inflammatory bowel disease and iron-deficiency anemia, clinicians first should determine whether iron-deficiency anemia is owing to inadequate intake or absorption, or loss of iron, typically from gastrointestinal bleeding. Active inflammation should be treated effectively to enhance iron absorption or reduce iron depletion. BEST PRACTICE ADVICE 9: Intravenous iron therapy should be given in individuals with inflammatory bowel disease, iron-deficiency anemia, and active inflammation with compromised absorption. BEST PRACTICE ADVICE 10: In individuals with portal hypertensive gastropathy and iron-deficiency anemia, oral iron supplements initially should be used to replenish iron stores. Intravenous iron therapy should be used in patients with ongoing bleeding who do not respond to oral iron therapy. BEST PRACTICE ADVICE 11: In individuals with portal hypertensive gastropathy and iron-deficiency anemia without another identified source of chronic blood loss, treatment of portal hypertension with nonselective ß-blockers can be considered. BEST PRACTICE ADVICE 12: In individuals with iron-deficiency anemia secondary to gastric antral vascular ectasia who have an inadequate response to iron replacement, consider endoscopic therapy with endoscopic band ligation or thermal methods such as argon plasma coagulation. BEST PRACTICE ADVICE 13: In patients with iron-deficiency anemia and celiac disease, ensure adherence to a gluten-free diet to improve iron absorption. Consider oral iron supplementation based on the severity of iron deficiency and patient tolerance, followed by intravenous iron therapy if iron stores do not improve. BEST PRACTICE ADVICE 14: Deep enteroscopy performed in patients with iron-deficiency anemia suspected to have small-bowel bleeding angioectasias should be performed with a distal attachment to improve detection and facilitate treatment. Small-bowel angioectasias may be treated with ablative thermal therapies such as argon plasma coagulation or with mechanical methods such as hemostatic clips. BEST PRACTICE ADVICE 15: Endoscopic treatment of angioectasias should be accompanied with iron replacement. Medical therapy for small-bowel angioectasias should be reserved for compassionate treatment in refractory cases when iron replacement and endoscopic therapy are ineffective.

Serum Ammonia Levels Do Not Correlate With Overt Hepatic Encephalopathy Severity in Hospitalized Patients With Cirrhosis.

Although ammonia is involved in the pathophysiology of hepatic encephalopathy (HE), the use of ammonia levels in clinical practice is problematic.1-3 For example, in a study of 551 patients with overt HE (OHE) receiving lactulose who had ammonia levels tested, only 60% had an increased ammonia level (defined as >72 µmol/L).2 Overall, there was no correlation observed between lactulose dose and whether ammonia levels were obtained (ie, presence/absence of increased ammonia level did not guide therapy), or between time to OHE resolution and ammonia levels.2 Additionally, there is substantial interlaboratory variability in sample handling and processing, which may affect ammonia measurements.4.

The Role of Imaging for Gastrointestinal Bleeding: Consensus Recommendations From the American College of Gastroenterology and Society of Abdominal Radiology.

Gastrointestinal (GI) bleeding is the most common GI diagnosis leading to hospitalization within the United States. Prompt diagnosis and treatment of GI bleeding is critical to improving patient outcomes and reducing high healthcare utilization and costs. Radiologic techniques including computed tomography angiography, catheter angiography, computed tomography enterography, magnetic resonance enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan) are frequently used to evaluate patients with GI bleeding and are complementary to GI endoscopy. However, multiple management guidelines exist which differ in the recommended utilization of these radiologic examinations. This variability can lead to confusion as to how these tests should be used in the evaluation of GI bleeding. In this document, a panel of experts from the American College of Gastroenterology and Society of Abdominal Radiology provide a review of the radiologic examinations used to evaluate for GI bleeding including nomenclature, technique, performance, advantages, and limitations. A comparison of advantages and limitations relative to endoscopic examinations is also included. Finally, consensus statements and recommendations on technical parameters and utilization of radiologic techniques for GI bleeding are provided.

The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations.

Gastrointestinal (GI) bleeding is the most common GI diagnosis leading to hospitalization within the United States. Prompt diagnosis and treatment of GI bleeding is critical to improving patient outcomes and reducing high health care utilization and costs. Radiologic techniques including CT angiography, catheter angiography, CT enterography, MR enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan) are frequently used to evaluate patients with GI bleeding and are complementary to GI endoscopy. However, multiple management guidelines exist, which differ in the recommended utilization of these radiologic examinations. This variability can lead to confusion as to how these tests should be used in the evaluation of GI bleeding. In this document, a panel of experts from the American College of Gastroenterology and Society of Abdominal Radiology provide a review of the radiologic examinations used to evaluate for GI bleeding including nomenclature, technique, performance, advantages, and limitations. A comparison of advantages and limitations relative to endoscopic examinations is also included. Finally, consensus statements and recommendations on technical parameters and utilization of radiologic techniques for GI bleeding are provided. © Radiological Society of North America and the American College of Gastroenterology, 2024. Supplemental material is available for this article. This article is being published concurrently in American Journal of Gastroenterology and Radiology. The articles are identical except for minor stylistic and spelling differences in keeping with each journal's style. Citations from either journal can be used when citing this article. See also the editorial by Lockhart in this issue.

Update on ischemic hepatitis.

PURPOSE OF REVIEW: Ischemic hepatitis (IH) refers to diffuse liver injury secondary to hypoperfusion. The condition is usually seen in the critical care setting and is associated with significant mortality. IH typically occurs in the setting of systemic hypotension superimposed on some form of underlying cardiac dysfunction. This review aims to report what is known and what is new about the etiology, pathophysiology, and clinical features associated with IH. RECENT FINDINGS: In recent years, studies on IH have largely confirmed earlier reports regarding etiologies, comorbid conditions, and associated mortality. Recent study has also shed light on the potential treatment of IH with N -acetyl-cysteine (NAC). SUMMARY: IH is typically associated with underlying cardiac disease, and patients with IH have a very high mortality rate. Treatment remains largely supportive, although the utility of agents such as NAC are being explored.

Noninvasive assessment of liver fibrosis and portal hypertension.

PURPOSE OF REVIEW: The result of ongoing liver injury - and disease, regardless of cause - is fibrosis, and fibrosis appears to be a critically important result of ongoing injury. Further, in a number of different liver diseases, the presence of fibrosis has prognostic value. Therefore, the assessment of fibrosis is of critical clinical importance. Given the importance of fibrosis, there has been a rapid evolution in the use of noninvasive liver tests. This review highlights a number of the core principles surrounding. RECENT FINDINGS: The use of noninvasive test has progressed rapidly over the last decade and data are rapidly accumulating. New terminology has been adapted by the American Association for the Study of Liver Disease (AASLD) for noninvasive assessment of liver disease and termed 'NILDA' (Non-Invasive Liver Disease Assessment). Blood based such as APRI and or FIB-4 and imaging tests such as liver stiffness measurement (LSM) have moderate to high degrees of accuracy for detection of advanced liver fibrosis (≥ F2) and even higher accuracy for detection of severe fibrosis (F4 or cirrhosis). NILDA are particularly effective at the ends of the liver disease spectrum. For example, a very low LSM (less than 7 kPa) essentially excludes significant fibrosis or portal hypertension, and a very high LSM (> 25 kPa) makes significant fibrosis with portal hypertension (cirrhosis) highly likely. SUMMARY: NILDA are currently front and center in terms of assessment of the severity of liver disease. In all patients with known or suspected liver disease, noninvasive blood tests, including APRI and or FIB-4, should be the initial choice to assess the severity of liver fibrosis and/or portal hypertension. In most patients, these tests should be followed with imaging evaluation. The most commonly available imaging is LSM, which appears to be more accurate in predicting fibrosis severity, and is superior to blood tests in the assessment of portal hypertension. In situations in which there is diagnostic uncertainly, liver biopsy with or without HVPG remains an important consideration.

Diagnostic utility of CT angiography compared with endoscopy in patients with acute GI hemorrhage.

BACKGROUND AND AIMS: Because it is minimally invasive, CT angiography (CTA) has emerged as an attractive diagnostic tool for investigation of acute GI hemorrhage. METHODS: This study examined patients with acute GI bleeding who underwent CTA. RESULTS: CTA was the initial diagnostic examination in 177 patients, identifying upper and lower GI bleeding lesions in 16 and 27 patients, respectively. In 103 patients with an initial negative CTA, 78 had endoscopy (32 EGD and 46 colonoscopy/flexible sigmoidoscopy), of whom 52 (67%) had a bleeding lesion identified, including 23 with a high-risk bleeding lesion requiring therapy. Peptic ulcer disease and diverticular bleeding were the most commonly identified bleeding lesions. With endoscopy as a criterion standard, the sensitivity of CTA for the detection of a source of GI bleeding was 20%. CONCLUSIONS: CTA has very poor sensitivity for identification of a GI bleeding source or lesion, suggesting that CTA should not be used as an initial diagnostic test.