Fasting Blood Ammonia Predicts Risk and Frequency of Hepatic Encephalopathy Episodes in Patients With Cirrhosis

Hepatic encephalopathy: risk identification and prophylaxis approaches

Hepatic encephalopathy (HE) is a debilitating neurological condition associated with cirrhosis, characterized by cognitive impairment ranging from minimal to overt symptoms. It significantly impacts patients' quality of life and substantially burdens healthcare systems. This review examines current prophylactic strategies for HE, focusing on established treatments, emerging therapies, and predictive tools to identify high-risk patients. Traditional treatments such as lactulose and rifaximin remain the cornerstone of HE management, effectively reducing ammonia levels and preventing recurrence. However, novel approaches like L-ornithine L-aspartate, albumin infusions, and antioxidants like resveratrol show promise in further improving outcomes by addressing underlying pathophysiological mechanisms, including systemic inflammation and gut dysbiosis. Developing predictive models, such as the AMMON-OHE score and clinical-genetic risk assessments, enhances the ability to tailor preventive interventions to individual patient profiles. These advancements are crucial in mitigating the incidence of overt HE, reducing hospital admissions, and improving patient survival rates. The future of HE management lies in personalized medicine, targeting specific inflammatory and metabolic pathways, with the potential integration of genetic manipulation. Continued research is essential to refine these strategies, ultimately aiming to improve the prognosis and quality of life for cirrhotic patients at risk of HE.

Small Intestinal Bacterial Overgrowth Is a Predictor of Overt Hepatic Encephalopathy in Patients with Liver Cirrhosis

Objective: Liver cirrhosis (LC) progression induces intestinal microbiota abnormalities, such as small intestinal bacterial overgrowth (SIBO), and these changes lead to the inflow of gut pathogens and their degradation products into the vessels, causing cirrhotic complications such as hepatic encephalopathy (HE). Methods: To clarify the relationship between the development of overt HE and SIBO, we conducted a three-year observation after assessment of SIBO in patients with LC. Results: In the analysis of 107 patients, with a mean follow-up duration of 29.4 months, 31 were diagnosed with SIBO and 30 with covert HE. In the Cox multivariate regression analysis for prognosis, the Child-Pugh score, blood urea nitrogen level, and the Union for International Cancer Control (UICC) stage of hepatocellular carcinoma were derived using the following five factors: white blood cell count, blood urea nitrogen level, Child-Pugh score, UICC stage, and serum aspartate aminotransferase and alkaline phosphatase levels (p = 0.002, hazard ratio [HR] 3.733, 95% confidence interval [CI] 1.592-8.754, p = 0.001, HR 1.076, 95% CI 1.030-1.123, and p < 0.001, HR 2.767, 95% CI 1.780-4.302, respectively). Furthermore, in the Cox multivariate regression analysis for overt HE development, covert HE and methane-producing SIBO were derived using the following four factors: methane-producing SIBO, UICC stage, covert HE, and serum ammonia levels (p = 0.038, HR 5.008, 95% CI 1.096-22.892 and p = 0.006, HR 8.597, 95% CI 1.881-39.291, respectively). Conclusions: M-SIBO positivity was a significant predictor of overt HE.

Blood ammonia concentration measurement - effects of sampling site and cirrhosis during induced hyperammonaemia

BACKGROUND

Ammonia is implicated in hepatic encephalopathy (HE) and prognostic in cirrhosis. Venous ammonia concentration, yielding similar correlation with HE grades as arterial, has become the preferred practise but comparative data are limited.

AIM

To quantify effect of sampling site on ammonia concentration in healthy persons and patients with cirrhosis.

METHODS

Ammonia concentrations were measured by arterial and femoral venous blood sampling in ten healthy men and ten male patients with cirrhosis before and during hyperammonaemia induced by ammonia infusion. Cubital vein samples were included during the infusion.

RESULTS

At baseline, arterial-venous concentration gaps were similar (p = 0.15) in healthy persons [14 (10-19) and 8 (4-12) µmol/L] and patients with cirrhosis [53 (32-74) and 40 (23-57) µmol/L]. Ammonia infusion increased arterial-venous concentration gaps in both groups [115 (97-133) and 61 (31-90) vs. 175 (123-227) and 134 (65-203) µmol/L]. Mean ammonia concentration difference between groups during hyperammonaemia was 72 (42-103) µmol/L (p < 0.001) and independent of sampling site. Cubital and femoral vein concentrations were comparable (p = 0.26). In cirrhosis, calculated upper limit normal values (ULN) were comparable for arterial and venous blood at baseline [2.0 (1.2-2.8) and 2.1 (1.2-3.0), p = 0.74] and during hyperammonaemia [6.7 (4.7-8.7) and 6.2 (4.4- 8.1), p = 0.44].

CONCLUSIONS

We found clinically meaningful intra-individual arterial-venous concentration gaps in both healthy persons and patients with cirrhosis at any ammonia concentration. Inter-group concentration differences after induced hyperammonaemia were relatively constant across sampling sites which supports clinical use of venous sampling. ULN-normalised ammonia concentrations were valid for both arterial and venous sampling.

Ammonia-induced stress response in liver disease progression and hepatic encephalopathy

Ammonia levels are orchestrated by a series of complex interrelated pathways in which the urea cycle has a central role. Liver dysfunction leads to an accumulation of ammonia, which is toxic and is strongly associated with disruption of potassium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation, hypoxaemia and dysregulation of neurotransmission. Hyperammonaemia is a hallmark of hepatic encephalopathy and has been strongly associated with liver-related outcomes in patients with cirrhosis and liver failure. In addition to the established role of ammonia as a neurotoxin in the pathogenesis of hepatic encephalopathy, an increasing number of studies suggest that it can lead to hepatic fibrosis progression, sarcopenia, immune dysfunction and cancer. However, elevated systemic ammonia levels are uncommon in patients with metabolic dysfunction-associated steatotic liver disease. A clear causal relationship between ammonia-induced immune dysfunction and risk of infection has not yet been definitively proven. In this Review, we discuss the mechanisms by which ammonia produces its diverse deleterious effects and their clinical relevance in liver diseases, the importance of measuring ammonia levels for the diagnosis of hepatic encephalopathy, the prognosis of patients with cirrhosis and liver failure, and how our knowledge of inter-organ ammonia metabolism is leading to the development of novel therapeutic approaches.

Other causes of neurocognitive impairment than covert hepatic encephalopathy (CHE) are very frequent, either alone or associated with CHE, in cirrhotic patients with cognitive complaints

BACKGROUND/AIMS

Although it is well admitted that cirrhotic patients display various causes of neurocognitive impairment (NI) hampering the diagnosis of covert hepatic encephalopathy (CHE), those are almost never investigated per se. The aims of this study were, in cirrhotic patients displaying cognitive complaints explored by a complete multimodal work-up, to assess: (1) the prevalence of CHE and/or that of other causes of NI and (2) their outcomes, according to the cause of NI.

METHODS

Prospective cohort of cirrhotic patients referred in a dedicated clinic because of cognitive complaints. Work-up included a complete neuropsychological assessment, electroencephalogram (EEG) and brain magnetic resonance imaging with spectroscopy. The diagnosis of CHE was made by an adjudication committee involving the physicians/neuropsychologist.

RESULTS

One hundred and twenty-three patients were included (alcohol/MASLD/virus in 63/53/14%, MELD = 11). Sixty-six per cent of them were diagnosed with CHE; among them, 73% exhibited also other causes of NI, mainly cerebrovascular diseases/psychiatric. Among patients without CHE, 48% and 59% displayed pathological Psychometric Hepatic Encephalopathy Score and animal naming test, respectively. Clinical improvement was observed in 77% of the patients re-evaluated after specific management. CHE, but not the other causes of NI, was independently associated with OHE occurrence.

CONCLUSION

Other causes of NI than CHE are frequent in patients with cirrhosis, and not ruled-out by the classical tests dedicated to CHE. Prognosis was influenced by the cause of NI. The management of patients even without CHE led to clinical improvement, underlining the need for a multifaceted approach of cirrhotic patients with cognitive complaints.

Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

Investigation of Post-Transplant Mental Well-Being in Liver Transplant Recipients with Hepatic Encephalopathy

Objective: In this study, we aimed to examine the healing trend of hepatic encephalopathy after transplantation surgery in patients with liver failure. Method: We conducted this descriptive and cross-sectional study with the participation of liver transplant recipients. A personal information form, the West Haven Criteria (WHC), the Warwick-Edinburgh Mental Well-Being Scale (WEMWBS), and the Richmond Agitation Sedation Scale (RASS) were used for data collection. The data were analyzed using Chi-squared tests, ANOVA, and paired-samples t-tests. Results: As time progressed after liver transplantation, hepatic encephalopathy stages regressed (p < 0.01). We found that liver transplant recipients with end-stage hepatic encephalopathy were mostly within the first 6 months after transplantation, while patients with first-stage hepatic encephalopathy had received liver transplants more than 2 years ago (p < 0.01). Conclusions: The results of our study revealed that hepatic encephalopathy stages regressed after transplantation, but there was no complete recovery. This highlights the need to develop new treatment strategies other than liver transplantation for the treatment of hepatic encephalopathy.

Hepatic Encephalopathy-A Guide to Laboratory Testing

Hepatic encephalopathy (HE) remains both a clinical diagnosis and one of exclusion. Laboratory testing is largely focused on identifying precipitating factors. Ammonia levels in the blood can be helpful for the diagnosis of HE but are not required for confirmation. More recent literature is lending support to the prognostic capabilities of ammonia in cirrhosis, both in predicting future HE events and in determining outcomes in hospitalized patients. Accurate ammonia testing requires strict protocols to avoid common pitfalls in the measurement of this labile analyte. Future studies investigating the utility of other laboratory testing to diagnose, stage, or predict HE are encouraged.

Ammonia is associated with liver-related complications and predicts mortality in acute-on-chronic liver failure patients

The relationship between ammonia and liver-related complications (LRCs) in acute-on-chronic liver failure (ACLF) patients is not clearly established. This study aimed to evaluate the association between ammonia levels and LRCs in patients with ACLF. The study also evaluated the ability of ammonia in predicting mortality and progression of LRCs. The study prospectively recruited ACLF patients based on the APASL definition from the ACLF Research Consortium (AARC) from 2009 to 2019. LRCs were a composite endpoint of bacterial infection, overt hepatic encephalopathy (HE), and ascites. A total of 3871 cases were screened. Of these, 701 ACLF patients were enrolled. Patients with LRCs had significantly higher ammonia levels than those without. Ammonia was significantly higher in patients with overt HE and ascites, but not in those with bacterial infection. Multivariate analysis found that ammonia was associated with LRCs. Additionally, baseline arterial ammonia was an independent predictor of 30-day mortality, but it was not associated with the development of new LRCs within 30 days. In summary, baseline arterial ammonia levels are associated with 30-day mortality and LRCs, mainly overt HE and ascites in ACLF patients.

Hepatic encephalopathy: From novel pathogenesis mechanism to emerging treatments

Hepatic encephalopathy (HE) is one of the major complications of liver disease and significantly affects the quality of life (QOL) of patients. HE is common and frequently relapses in cirrhotic patients. The management of HE is supportive, and precipitating conditions should be eliminated. Most drugs used to treat HE are conventional and include nonabsorbable disaccharides such as lactulose, and antibiotics such as rifaximin. However, their therapeutic efficacy is still suboptimal, and novel therapeutic agents are urgently needed. In addition, the optimal management and diagnosis of minimal HE/covert HE are under debate. In this review, we focus on novel pathogenetic mechanisms such as central nervous system clearance, and emerging therapeutic targets of HE, such as fecal material transplantation. We also discuss different classifications and etiologies of HE.

Update in the Treatment of the Complications of Cirrhosis

Cirrhosis consists of 2 main stages: compensated and decompensated, the latter defined by the development/presence of ascites, variceal hemorrhage, and hepatic encephalopathy. The survival rate is entirely different, depending on the stage. Treatment with nonselective β-blockers prevents decompensation in patients with clinically significant portal hypertension, changing the previous paradigm based on the presence of varices. In patients with acute variceal hemorrhage at high risk of failure with standard treatment (defined as those with a Child-Pugh score of 10-13 or those with a Child-Pugh score of 8-9 with active bleeding at endoscopy), a pre-emptive transjugular intrahepatic portosystemic shunt (TIPS) improves the mortality rate and has become the standard of care in many centers. In patients with bleeding from gastrofundal varices, retrograde transvenous obliteration (in those with a gastrorenal shunt) and/or variceal cyanoacrylate injection have emerged as alternatives to TIPS. In patients with ascites, emerging evidence suggests that TIPS might be used earlier, before strict criteria for refractory ascites are met. Long-term albumin use is under assessment for improving the prognosis of patients with uncomplicated ascites and confirmatory studies are ongoing. Hepatorenal syndrome is the least common cause of acute kidney injury in cirrhosis, and first-line treatment is the combination of terlipressin and albumin. Hepatic encephalopathy has a profound impact on the quality of life of patients with cirrhosis. Lactulose and rifaximin are first- and second-line treatments for hepatic encephalopathy, respectively. Newer therapies such as L-ornithine L-aspartate and albumin require further assessment.

Clearance and production of ammonia quantified in humans by constant ammonia infusion - the effects of cirrhosis and ammonia targeting treatments

BACKGROUND & AIMS

Hyperammonaemia is a key pathological feature of liver disease and the primary driver of hepatic encephalopathy (HE). However, the relative roles of increased ammonia production and reduced clearance are poorly understood as is the action of ammonia-targeting HE drugs. We aimed to quantify whole-body ammonia metabolism in healthy persons and patients with cirrhosis and to validate our method by examining the effects of glycerol phenylbutyrate and lactulose + rifaximin treatment.

METHODS

Ten healthy men and ten male patients with cirrhosis were investigated by 90-minute constant ammonia infusion to achieve steady-state plasma ammonia. Whole-body ammonia clearance was calculated as infusion rate divided by steady-state concentration increase and ammonia production as clearance times baseline ammonia concentration. Participants were re-investigated after the ammonia targeting interventions.

RESULTS

In healthy persons, ammonia clearance was 3.5 (3.1-3.9) L/min and production 49 (35-63) μmol/min. Phenylbutyrate increased clearance by 11% (4-19%, p=0.009). Patients with cirrhosis had a 20% decreased ammonia clearance of 2.7 (2.1-3.3) L/min (p = 0.02) and a nearly tripled production to 131 (102-159) μmol/min (p<0.0001). Lactulose + rifaximin reduced production by 20% (2-37%, p=0.03). The infusion was generally well-tolerated save one hyperammonaemic patient with cirrhosis with possible bleeding unrelated to the infusion who developed clinical HE that reverted when infusion was discontinued.

CONCLUSIONS

Whole-body ammonia clearance and production may be measured separately by the technique used. The method identified a lower clearance and a higher production in patients with cirrhosis, and showed that phenylbutyrate increases clearance, whereas lactulose + rifaximin reduces production. The method may be used to examine a range of questions related to normo-/pathophysiology and ammonia-targeting treatment mechanisms.

IMPACT AND IMPLICATIONS

High blood ammonia plays a key role in liver cirrhosis related brain dysfunction. However, the relative roles of increased ammonia production and reduced ammonia clearance are poorly understood as is the action of ammonia-targeting treatments. This study presents a relatively simple test to measure ammonia metabolism. By use of this test, it was possible to show that patients with liver cirrhosis have decreased ammonia clearance and increased ammonia production compared with healthy persons and to quantify distinctively different ammonia-targeting treatment effects. The test presented holds several perspectives for future studies of normal physiology and pathophysiology, not least in regard to elucidating effects of ammonia-targeting therapies.

CLINICAL TRIAL NUMBER

ClinicalTrials.gov (1-16-02-297-20).

Prediction and prevention of the first episode of overt hepatic encephalopathy in patients with cirrhosis

Hepatic encephalopathy (HE) is one of the most important complications of patients with liver cirrhosis. In addition, HE is associated with a dismal prognosis and has detrimental effects on patients' quality of life. Thus, it is of pivotal importance to identify patients at high risk for overt HE (OHE) in whom primary prophylaxis may be justified. In this narrative review, we aim to provide insight into predictors and prediction tools for a first-time episode of OHE and to scrutinize the current level of evidence of primary prophylaxis. In recent decades, several cognitive tests, composite scores, and blood-based biomarkers have been demonstrated to be predictive of a first-time episode of OHE. Among the best validated are the established tests for minimal HE, such as the Psychometric Hepatic Encephalopathy Score, determination of the critical flicker frequency, Stroop EncephalApp, or the Animal Naming Test. Individualized risk stratification using blood-based biomarkers and cross-sectional imaging (sarcopenia and spontaneous portosystemic shunts) is coming to the fore, but validation in larger multicenter cohorts is often lacking. On the basis of current evidence, a recommendation for primary prophylaxis of a first episode of OHE cannot be made in general. Only 2 studies have investigated the prevention of a first-time OHE episode as the primary endpoint. In this narrative review, we provide a concise overview of the current evidence levels on prediction tools and pharmacological prevention of a first episode of OHE. In addition, we give an outlook on future research targets to improve knowledge on this important topic.

Impact of ammonia levels on outcome in clinically stable outpatients with advanced chronic liver disease

Background & Aims

Ammonia levels predicted hospitalisation in a recent landmark study not accounting for portal hypertension and systemic inflammation severity. We investigated (i) the prognostic value of venous ammonia levels (outcome cohort) for liver-related outcomes while accounting for these factors and (ii) its correlation with key disease-driving mechanisms (biomarker cohort).

Methods

(i) The outcome cohort included 549 clinically stable outpatients with evidence of advanced chronic liver disease. (ii) The partly overlapping biomarker cohort comprised 193 individuals, recruited from the prospective Vienna Cirrhosis Study (VICIS: NCT03267615).

Results

(i) In the outcome cohort, ammonia increased across clinical stages as well as hepatic venous pressure gradient and United Network for Organ Sharing model for end-stage liver disease (2016) strata and were independently linked with diabetes. Ammonia was associated with liver-related death, even after multivariable adjustment (adjusted hazard ratio [aHR]: 1.05 [95% CI: 1.00-1.10]; p = 0.044). The recently proposed cut-off (≥1.4 × upper limit of normal) was independently predictive of hepatic decompensation (aHR: 2.08 [95% CI: 1.35-3.22]; p <0.001), non-elective liver-related hospitalisation (aHR: 1.86 [95% CI: 1.17-2.95]; p = 0.008), and - in those with decompensated advanced chronic liver disease - acute-on-chronic liver failure (aHR: 1.71 [95% CI: 1.05-2.80]; p = 0.031). (ii) Besides hepatic venous pressure gradient, venous ammonia was correlated with markers of endothelial dysfunction and liver fibrogenesis/matrix remodelling in the biomarker cohort.

Conclusions

Venous ammonia predicts hepatic decompensation, non-elective liver-related hospitalisation, acute-on-chronic liver failure, and liver-related death, independently of established prognostic indicators including C-reactive protein and hepatic venous pressure gradient. Although venous ammonia is linked with several key disease-driving mechanisms, its prognostic value is not explained by associated hepatic dysfunction, systemic inflammation, or portal hypertension severity, suggesting direct toxicity.

Impact and implications

A recent landmark study linked ammonia levels (a simple blood test) with hospitalisation/death in individuals with clinically stable cirrhosis. Our study extends the prognostic value of venous ammonia to other important liver-related complications. Although venous ammonia is linked with several key disease-driving mechanisms, they do not fully explain its prognostic value. This supports the concept of direct ammonia toxicity and ammonia-lowering drugs as disease-modifying treatment.

Blood ammonia in patients with chronic liver diseases: A better defined role in clinical practice

Ammonia is one of the main players in the pathogenesis of hepatic encephalopathy (HE) in patients with chronic liver diseases. The usefulness of measuring ammonemia has been debated since many years. New data reveal that besides helping in the differential diagnosis of HE, ammonemia could be a prognostic marker not only in patients with HE, but also in patients without any neurological symptoms, suggesting a potential toxic role of ammonia beyond the brain. Finally, targeting ammonemia while monitoring therapeutic response could be a way to improve outcomes in patients with HE.

EASL Clinical Practice Guidelines on the management of hepatic encephalopathy

The EASL Clinical Practice Guidelines (CPGs) on the management of hepatic encephalopathy (HE) present evidence-based answers to a set of relevant questions (where possible, formulated in PICO [patient/population, intervention, comparison and outcomes] format) on the definition, diagnosis, differential diagnosis and treatment of HE. The document does not cover the pathophysiology of HE and does not cover all available treatment options. The methods through which it was developed and any information relevant to its interpretation are also provided.

Heretical thoughts into hepatic encephalopathy

Clinical progress in the development of new diagnostic modalities and therapeutic strategies for the management of patients with hepatic encephalopathy has lagged behind the vast knowledge that has been generated from basic studies. In this article, we critically assess matters that should be revisited, such as definition, classification, diagnosis and grading of hepatic encephalopathy, which are difficult to apply reproducibly using the current criteria. Many lines of investigation have confirmed that hepatic encephalopathy is irreversible in many patients and suggest the need for further studies focussing on mechanisms of neuronal injury and death, to guide future drug development for these patients. The clinical evidence behind using lactulose for all severities of hepatic encephalopathy, which is currently considered the standard of care, is poor and placebo-controlled trials for hepatic encephalopathy should be considered ethically sound. This expert opinion identifies current challenges in hepatic encephalopathy and highlights areas which require further debate and investigation in order to help advance the field both scientifically and clinically.

Sex is associated with differences in oxidative stress and susceptibility to severe hepatic encephalopathy in bile-duct ligated rats

Hepatic encephalopathy (HE) is a debilitating neurological complication of chronic liver disease (CLD). Hyperammonemia plays an important role in HE's pathogenesis, acting synergistically with systemic oxidative stress. During CLD, muscle plays a compensatory role in detoxifying ammonia, and therefore muscle loss leads to an increase in the risk of developing HE. With most animal studies involving males, sex's impact on the development of CLD and associated complications such as HE and muscle loss remains unknown. Therefore, we aimed to identify the impact of sex on CLD, HE, and muscle mass loss in a rodent model of CLD. Liver injury markers, hyperammonemia, oxidative stress, muscle mass and ammonia clearance were measured in female and male bile-duct ligated (BDL) rats. In addition, covert HE was assessed in females while ammonia-precipitated severe HE was assessed in female and male BDL rats, and male BDL rats treated with allopurinol (100mg/kg), an antioxidant (xanthine oxidase inhibitor). Female BDL developed CLD and HE (impaired motor-coordination and night activity) compared to respective SHAM. Hyperammonemia and muscle ammonia clearance were similar between female and male BDL. However, only female BDL rats did not develop muscle loss, brain edema, and short-term memory impairment (vs. female SHAM) and systemic oxidative stress and decreased albumin levels (vs. male BDL). Furthermore, both female BDL and allopurinol-treated male BDL rats were protected against ammonia-induced overt HE. In conclusion, female and male BDL rats develop distinct features of CLD and HE, with systemic oxidative stress playing a pivotal role in the susceptibility to ammonia precipitated overt HE.

Hepatic encephalopathy

Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.

Hepatic Encephalopathy: From Metabolic to Neurodegenerative

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome of both acute and chronic liver disease. As a metabolic disorder, HE is considered to be reversible and therefore is expected to resolve following the replacement of the diseased liver with a healthy liver. However, persisting neurological complications are observed in up to 47% of transplanted patients. Several retrospective studies have shown that patients with a history of HE, particularly overt-HE, had persistent neurological complications even after liver transplantation (LT). These enduring neurological conditions significantly affect patient's quality of life and continue to add to the economic burden of chronic liver disease on health care systems. This review discusses the journey of the brain through the progression of liver disease, entering the invasive surgical procedure of LT and the conditions associated with the post-transplant period. In particular, it will discuss the vulnerability of the HE brain to peri-operative factors and post-LT conditions which may explain non-resolved neurological impairment following LT. In addition, the review will provide evidence; (i) supporting overt-HE impacts on neurological complications post-LT; (ii) that overt-HE leads to permanent neuronal injury and (iii) the pathophysiological role of ammonia toxicity on astrocyte and neuronal injury/damage. Together, these findings will provide new insights on the underlying mechanisms leading to neurological complications post-LT.

A pilot study of golexanolone, a new GABA-A receptor-modulating steroid antagonist, in patients with covert hepatic encephalopathy

BACKGROUND & AIMS

Golexanolone is a novel small molecule GABA-A receptor-modulating steroid antagonist under development for the treatment of cognitive and vigilance disorders caused by allosteric over-activation of GABA-A receptors by neurosteroids. It restored spatial learning and motor coordination in animal models of hepatic encephalopathy (HE) and mitigated the effects of intravenous allopregnanolone in healthy adults in a dose-dependent fashion. Herein, we report data on the safety, pharmacokinetics (PK) and efficacy of golexanolone in adult patients with cirrhosis.

METHODS

Following single/multiple ascending dose studies, adults with Child-Pugh A/B cirrhosis and abnormal continuous reaction time (CRT) on screening were randomized to 3 weeks' dosing with golexanolone (10, 40 or 80 mg BID) or placebo. CRT, psychometric hepatic encephalopathy score (PHES), animal naming test (ANT), Epworth sleepiness scale (ESS) and electroencephalogram (mean dominant frequency [MDF]; delta+theta/alpha+beta ratio [DT/AB]) were obtained at baseline, 10, and 21 days.

RESULTS

Golexanolone exhibited satisfactory safety and PK. Baseline characteristics were similar between the 12 and 33 patients randomized to placebo or golexanolone, respectively. By prespecified analyses, golexanolone was associated with directionally favourable changes vs. placebo in ESS (p = 0.047), MDF (p = 0.142) and DT/AB (p = 0.021). All patients also showed directionally favourable changes in CRT, PHES and ANT, but with no statistical difference between golexanolone and placebo. Post hoc analyses taking into account the variability and improvement in CRT, PHES and ANT observed between screening and baseline suggested an efficacy signal by cognitive measures as well.

CONCLUSION

Golexanolone was well tolerated and associated with improvement in cognitive performance. These results implicate GABA-A receptor-modulating neurosteroids in the pathogenesis of HE and support the therapeutic potential of golexanolone.

LAY SUMMARY

Many patients with cirrhosis experience subtle but disabling cognitive problems, including sleepiness and poor attention span, that impair their ability to be gainfully employed or carry out activities of daily living. This pilot study tested the hypothesis that these problems with cognition, for which there is no approved treatment, might be improved by an experimental drug, golexanolone, designed to normalize the function of receptors which inhibit brain function. The results of this study suggest that golexanolone is well tolerated and may improve cognition, as reflected by measures of sleepiness, attention span and brain wave activity, paving the way for future larger studies of this promising experimental drug.

CLINICAL TRIAL REGISTRATION NUMBER

EudraCT 2016-003651-30.

Diagnosis and Management of Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a severe complication of cirrhosis. The prevalence of overt HE (OHE) ranges from 30% to 45%, whereas the prevalence of minimal HE (MHE) is as high as 85% in some case series. Widespread use of transjugular intrahepatic portosystemic shunt to control complications related to portal hypertension is associated with an increase in HE incidence. If the diagnosis of OHE remains simple in most cases, then the diagnosis of MHE is less codified because of many differential diagnoses with different therapeutic implications. This review analyzes current knowledge about the pathophysiology, diagnosis, and different therapeutic options of HE.

Lights and Shadows in Hepatic Encephalopathy Diagnosis

Hepatic encephalopathy (HE) is a form of brain dysfunction that is caused by liver insufficiency and/or portal-systemic shunting. The exact nature of HE is debated; as such, conflicting uses of the term "HE" may cause inconsistencies in its detection and management. This review highlights the meaning of the term "HE" on the basis of its historical origins and current consensus. It also provides criteria for the diagnosis of the condition based on its phenotypes and risk factors for its occurrence. The procedure for differential diagnosis from other conditions which result in similar phenotypes is considered, together with precipitants and confounders. Finally, the current multidimensional approach for the correct clinical reporting of HE episodes is discussed.

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.

Serum ammonia is a strong prognostic factor for patients with acute-on-chronic liver failure

Ammonia is thought to be central to the pathogenesis of hepatic encephalopathy (HE), but its prognostic role in acute-on-chronic liver failure (ACLF) is still unknown. We aimed to determine the association between serum ammonia level and short-term prognosis in ACLF. Furthermore, we performed an in-depth evaluation of the independent effect of serum ammonia level on the short-term prognosis of hepatitis B virus (HBV) reactivation-induced ACLF patients. We identified 174 patients as part of prospective observational studies in patients with ACLF. Plasma ammonia levels were measured on admission, and several prognostic scores were used to determine the prognostic effect of ammonia. The 28-day patient survival was determined. Receiver operating characteristic analysis was used to identify the cut-off points for ammonia values, and multivariable analysis was performed using the Cox proportional hazard regression model. Plasma ammonia was significantly higher in nonsurvivors (83.53 ± 43.78 versus 67.13 ± 41.77 µmol/L, P = 0.013), and ACLF patients with hyperammonemia had significantly higher 28-day mortality than those without hyperammonemia. Ammonia was also closely related to ACLF grade (P < 0.001) and organ failure, including liver (P = 0.048), coagulation (P < 0.001) and brain (P < 0.001). HBV reactivation serves as the main precipitating factor in the ACLF population. Subgroup analysis showed that ammonia is also a strong prognostic factor in the HBV reactivation-induced ACLF population. Ammonia level is closely correlated with failure of other organs and is an independent risk factor for mortality in ACLF and the special population defined as HBV reactivation-related ACLF. Based on the results from our study, we measured serum ammonia in the population with ACLF, which strongly indicates their prognosis. It serves as an important biomarker and a therapeutic target.

Preclinical evaluation of liposome-supported peritoneal dialysis for the treatment of hyperammonemic crises

Liposome-supported peritoneal dialysis (LSPD) with transmembrane pH-gradient liposomes was previously shown to enhance ammonia removal in cirrhotic rats and holds promise for the treatment of hyperammonemic crises-associated disorders. The main objective of this work was to conduct the preclinical evaluation of LSPD in terms of pharmacokinetics, ammonia uptake, and toxicology to seek regulatory approval for a first-in-human study. The formulation containing citric acid-loaded liposomes was administered intraperitoneally at two different doses once daily for ten days to healthy minipigs. It was also tested in a domestic pig model of hyperammonemia. The pharmacokinetics of citric acid and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was linear following intraperitoneal administration of medium and high dose. There was no systemic accumulation following daily doses over ten days. The systemic exposure to phospholipids remained low. Furthermore, the liposome-containing peritoneal fluid contained significantly higher ammonia levels than the liposome-free control, demonstrating efficient ammonia sequestration in the peritoneal space. This was indeed confirmed by the ability of LSPD to decrease plasmatic ammonia levels in artificially induced hyperammonemic pigs. LSPD was well tolerated, and no complement activation-related pseudoallergy reactions were observed. The safety profile, the linear pharmacokinetics of citric acid following repeated administrations of LSPD as well as the linear dose-dependent ammonia sequestration in the peritoneal space provide a strong basis for the clinical investigation of LSPD.

An Oral Formulation of the Probiotic, Bacillus subtilis HU58, Was Safe and Well Tolerated in a Pilot Study of Patients with Hepatic Encephalopathy

Background

Hepatic encephalopathy often results in high blood ammonia levels because of inefficient ammonia processing by the liver. Lactulose treatment promotes the growth of urease-producing gut bacteria and a reduced colon pH, thus reducing blood ammonia absorption. It is thought that probiotics as an add-on therapy may be beneficial. Patients and Methods. Bacillus subtilis HU58 was tested for safety and tolerability in patients with hepatic encephalopathy taking lactulose in this double-bind, placebo-controlled, 4-week pilot study. Study participants received one dose of B. subtilis HU58 or placebo (orally) for the first five days and two daily doses thereafter. Participants were monitored for safety and blood ammonia levels.

Results

Forty patients participated (placebo, 11; probiotic, 29). Baseline characteristics were generally comparable; the mean baseline blood ammonia level was somewhat higher in the probiotic group. Mild or moderate treatment-emergent adverse events (TEAEs) were reported in 27.3% and 17.2% of patients in the placebo and probiotic groups, respectively; no severe TEAEs were reported. One patient (9.1%) taking placebo and two (6.9%) taking the probiotic experienced serious TEAEs (SAEs); none resulted in study discontinuation and all were considered to have no/unlikely relationship to the study product. There were no significant differences in the mean percent change (MPC) of blood ammonia levels between groups, though the probiotic group exhibited a trend toward a milder increase. Stratification of the probiotic group by baseline blood ammonia level (>60 μg/dL and ≤60 μg/dL) resulted in a significantly reduced MPC in the >60 μg/dL subgroup (MPC (SD); ≤60 μg/dL (n = 14), 35.3% (73.3); >60 μg/dL (n = 14), −26.5% (24.4); p = 0.0087).

Conclusions

Daily treatment with oral B. subtilis HU58 was safe and well tolerated over a 4-week period in patients with hepatic encephalopathy, and a significantly reduced MPC of blood ammonia level was observed in patients with a baseline level >60 µg/dL.

Important Unresolved Questions in the Management of Hepatic Encephalopathy: An ISHEN Consensus

Management of hepatic encephalopathy (HE) remains challenging from a medical and psychosocial perspective. Members of the International Society for Hepatic Encephalopathy and Nitrogen Metabolism recognized 5 key unresolved questions in HE management focused on (i) driving, (ii) ammonia levels in clinical practice, (iii) testing strategies for covert or minimal HE, (iv) therapeutic options, and (v) nutrition and patient-reported outcomes. The consensus document addresses these topical issues with a succinct review of the literature and statements that critically evaluate the current science and practice, laying the groundwork for future investigations.

Ammonia Levels Do Not Guide Clinical Management of Patients With Hepatic Encephalopathy Caused by Cirrhosis

INTRODUCTION

Ammonia appears to play a major role in the pathophysiology of hepatic encephalopathy (HE), but its role in guiding management is unclear. We aimed to understand the impact of ammonia levels on inpatient HE management, hypothesizing that patients with elevated ammonia levels would receive more aggressive lactulose therapy than patients with normal ammonia or no ammonia level drawn.

METHODS

We examined patients with cirrhosis older than 18 years admitted for management of HE from 2005 to 2015. We additionally used propensity matching to control for confounding by the severity of underlying disease. Patients with an ammonia level taken at time of HE diagnosis were further separated into those with normal or elevated ammonia levels. The primary endpoint was the total lactulose (mL) amount (or dose) given in the first 48 hours of HE management.

RESULTS

One thousand two hundred two admissions with HE were identified. Ammonia levels were drawn in 551 (46%) patients; 328 patients (60%) had an abnormal ammonia level (>72 μmol/L). There were no significant differences in the Child-Pugh score, MELD, or Charlson Comorbidity Index in those with and without ammonia levels drawn. The average total lactulose dose over 48 hours was 167 and 171 mL in the no ammonia vs ammonia groups, respectively (P = 0.42). The average lactulose dose in patients with an elevated ammonia level was 161 mL, identical to the lactulose dose in patients with a normal ammonia level. There was no correlation between lactulose dose and ammonia level (R = 0.0026).

DISCUSSION

Inpatient management of HE with lactulose was not influenced by either the presence or level of ammonia level, suggesting that ammonia levels do not guide therapy in clinical practice.

An Investigation of PS-b-PEO Polymersomes for the Oral Treatment and Diagnosis of Hyperammonemia

Ammonia-scavenging transmembrane pH-gradient poly(styrene)-b-poly(ethylene oxide) polymersomes are investigated for the oral treatment and diagnosis of hyperammonemia, a condition associated with serious neurologic complications in patients with liver disease as well as in infants with urea cycle disorders. While these polymersomes are highly stable in simulated intestinal fluids at extreme bile salt and osmolality conditions, they unexpectedly do not reduce plasmatic ammonia levels in cirrhotic rats after oral dosing. Incubation in dietary fiber hydrogels mimicking the colonic environment suggests that the vesicles are probably destabilized during the dehydration of the intestinal chyme. The findings question the relevance of commonly used simulated intestinal fluids for studying vesicular stability. With the encapsulation of a pH-sensitive dye in the polymersome core, the local pH increase upon ammonia influx could be exploited to assess the ammonia concentration in the plasma of healthy and cirrhotic rats as well as in other fluids. Due to its high sensitivity and selectivity, this polymersome-based assay could prove useful in the monitoring of hyperammonemic patients and in other applications such as drug screening tests.

Prognostic Role of Ammonia in Patients With Cirrhosis

Ammonia is thought to be central to the pathogenesis of hepatic encephalopathy (HE), but its prognostic role in patients with cirrhosis and acute decompensation is unknown. The aims of this study were to determine the relationship between ammonia levels and severity of HE and its association with organ dysfunction and short-term mortality. We identified 498 patients from two institutions as part of prospective observational studies in patients with cirrhosis. Plasma ammonia levels were measured on admission and Chronic Liver Failure-Sequential Organ Failure Assessment criteria were used to determine the presence of organ failures. The 28-day patient survival was determined. Receiver operating characteristic analysis was used to identify the cutoff points for ammonia values, and multivariable analysis was performed using the Cox proportional hazard regression model. The 28-day mortality was 43.4%. Plasma ammonia correlated with severity of HE (P < 0.001), was significantly higher in nonsurvivors (93 [73-121] versus 67 [55-89] µmol/L, P < 0.001), and was an independent predictor of 28-day mortality (hazard ratio, 1.009, P < 0.001). An ammonia level of 79.5 µmol/L had sensitivity of 68.1% and specificity of 67.4% for predicting 28-day mortality. An ammonia level of ≥79.5 µmol/L was associated with a higher frequency of organ failures (liver [P = 0.004], coagulation [P < 0.001], kidney [P = 0.004], and respiratory [P < 0.001]). Lack of improvement in baseline ammonia at day 5 was associated with high mortality (70.6%). Conclusion: Ammonia level correlates with not only the severity of HE but also the failure of other organs and is an independent risk factor for mortality; lack of improvement in ammonia level is associated with high risk of death, making it an important biomarker and a therapeutic target.

Why and when to measure ammonemia in cirrhosis?

Hyperammonemia plays a key role in the pathophysiology of hepatic encephalopathy (HE) and most HE treatments are ammonia-lowering drugs. However, the usefulness of measuring ammonemia in routine practice remains controversial and not recommended systematically even when neurological symptoms are present. First, ammonemia measurement should be carefully performed in order to avoid a falsely elevated result. When performed, a normal ammonemia in a cirrhotic patient with neurological symptoms should lead to reconsider the diagnosis of HE. Indeed, literature data show that most cirrhotic patients with HE have an elevated ammonemia, which is however individually poorly correlated with the severity of symptoms. Nevertheless, elevated ammonemia seems to be a factor of bad prognosis in cirrhosis. A decrease in ammonemia after treatments is well proven but it is not determined whether it is associated with clinical efficacy. Repeated measurements could be useful in this context, especially in non-responders, to help differentiating other causes of encephalopathy, such as drug induced. In acute liver failure, the prognostic value of hyperammonemia is well described and could help an early recognition the most severe forms of this disease. We will also discuss how integrating ammonemia into the diagnostic work-up of liver failure and/or encephalopathy. Ammonemia is also essential to diagnose urea cycle disorders or drug toxicity that both need specific interventions.

Current Diagnosis and Classification of Hepatic Encephalopathy

Hepatic encephalopathy is a brain dysfunction caused by liver insufficiency and/or portal-systemic shunt; it manifests as a wide spectrum of neurological or psychiatric abnormalities ranging from subclinical alterations to coma. It should be differentiated from other neurological/psychiatric disorders that can occur in patients with liver disease. Its classification needs to take into account the underlying condition, severity, course, precipitating factors, and-possibly-sensitivity to ammonia-lowering agents.

Gene Therapy for Treatment of Chronic Hyperammonemia in a Rat Model of Hepatic Encephalopathy

INTRODUCTION AND AIM

Hepatic encephalopathy (HE), caused by hyperammonemia resulting from liver disease, is a spectrum of neuropsychiatric and motor disorders that can lead to death. Existing therapies are deficient and alternative treatments are needed. We have shown that gene therapy with a baculovirus vector containing the glutamine synthetase (Bac-GS) gene is efficient for reducing ammonia levels in an acute hyperammonemia rat model. However, the most common condition resulting from liver disease is chronic hyperammonemia. In this work, Bac-GS was evaluated in bile-duct ligated rats, a chronic liver disease model with hyperammonemia and some characteristics of Type C HE.

MATERIAL AND METHODS

Bac-GS was tested for mediating GS overexpression in HeLa cells and H9C2 myotubes. For determining the utility of Bac-GS for the reduction of ammonia levels in a chronic hyperammonemia animal model, four groups of rats were treated: control, sham, ligated with Bac-GS and ligated with Bac-GFP. Baculoviruses were injected i.m. 18 days post-surgery. Blood was drawn 2, 3 and 4 weeks post-surgery and plasma ammonia concentrations were quantified.

RESULTS

In protein lysates of cells and myotubes transduced with Bac-GS, a 44 kDa band corresponding to GS was detected. Significant results were obtained in the hyperammonemic bile-duct ligated rat model, as plasma ammonia was reduced to normal levels 3 days after treatment with Bac-GS. Furthermore, a transitory effect of Bac-GS was observed.

CONCLUSION

Our results show that gene therapy by delivering GS is a promising alternative for treatment of hyperammonemia in acute-on-chronic liver failure patients with HE.

Ammonia modifies enteric neuromuscular transmission through glial γ-aminobutyric acid signaling

Impaired gut motility may contribute, at least in part, to the development of systemic hyperammonemia and systemic neurological disorders in inherited metabolic disorders, or in severe liver and renal disease. It is not known whether enteric neurotransmission regulates intestinal luminal and hence systemic ammonia levels by induced changes in motility. Here, we propose and test the hypothesis that ammonia acts through specific enteric circuits to influence gut motility. We tested our hypothesis by recording the effects of ammonia on neuromuscular transmission in tissue samples from mice, pigs, and humans and investigated specific mechanisms using novel mutant mice, selective drugs, cellular imaging, and enzyme-linked immunosorbent assays. Exogenous ammonia increased neurogenic contractions and decreased neurogenic relaxations in segments of mouse, pig, and human intestine. Enteric glial cells responded to ammonia with intracellular Ca²⁺ responses. Inhibition of glutamine synthetase and the deletion of glial connexin-43 channels in hGFAP::CreER^T2+/-/connexin43^f/f mice potentiated the effects of ammonia on neuromuscular transmission. The effects of ammonia on neuromuscular transmission were blocked by GABA_A receptor antagonists, and ammonia drove substantive GABA release as did the selective pharmacological activation of enteric glia in GFAP::hM3Dq transgenic mice. We propose a novel mechanism whereby local ammonia is operational through GABAergic glial signaling to influence enteric neuromuscular circuits that regulate intestinal motility. Therapeutic manipulation of these mechanisms may benefit a number of neurological, hepatic, and renal disorders manifesting hyperammonemia.NEW & NOTEWORTHY We propose that local circuits in the enteric nervous system sense and regulate intestinal ammonia. We show that ammonia modifies enteric neuromuscular transmission to increase motility in human, pig, and mouse intestine model systems. The mechanisms underlying the effects of ammonia on enteric neurotransmission include GABAergic pathways that are regulated by enteric glial cells. Our new data suggest that myenteric glial cells sense local ammonia and directly modify neurotransmission by releasing GABA.

Hepatic Encephalopathy: An Update on the Pathophysiology and Therapeutic Options

Hepatic encephalopathy is a spectrum of reversible neuropsychiatric abnormalities, seen in patients with liver dysfunction and/or portosystemic shunting. One of the most debilitating complications of cirrhosis, encephalopathy affects 30-45% of cirrhotics. In addition to significantly affecting the lives of patients and their caregivers, it is also associated with increased morbidity and mortality as well as significant utilization of health care resources. In this paper, we provide an overview on the pathophysiology, diagnosis, management and newer therapies of hepatic encephalopathy.

Serum 25-hydroxyvitamin D deficiency and hepatic encephalopathy in chronic liver disease

AIM

To investigate the relationship between 25-hydroxyvitamin D (25-OHD) deficiency and hepatic encephalopathy (HE) in patients with chronic liver disease (CLD).

METHODS

A retrospective analysis of the results of 392 adult patients with chronic liver disease who were assessed for liver transplantation between 2006 and 2010 was undertaken. HE, severity of CLD, nutritional status and 25-OHD were analysed in patients assessed for liver transplantation between 2006 and 2010. Patients who presented with acute, fulminant or subacute disease, with a primary diagnosis of liver cancer, were assessed for re-transplantation or who did not have a 25-OHD measurement were excluded from the analysis.

RESULTS

One hundred and sixty-five patients were included in this analysis. The mean age of all patients was 53 ± 8 years. Moderate to severe 25-OHD deficiency was identified in 49 patients of whom 36 had grade 2-3 HE compared with 13 patients who were not encephalopathic (P ≤ 0.0001). Mild 25-OHD deficiency was not associated with HE. There was a significant correlation between the severity of 25-OHD deficiency and the severity of liver disease (r = 0.39, P ≤ 0.0001) and disease severity and the presence of HE (P ≤ 0.0001). Importantly, individuals with 25-OHD deficiency were more likely to have a diagnosis of overt HE (OHE) at a significantly lower model for end stage liver disease (MELD) score than individuals without OHE (P ≤ 0.0001). This significant difference was observed with MELD scores from 10 to 38.

CONCLUSION

25-OHD deficiency was observed in the majority of patients with CLD and for the first time was found to be significantly worse in patients with OHE.

An update on the use of benzoate, phenylacetate and phenylbutyrate ammonia scavengers for interrogating and modifying liver nitrogen metabolism and its implications in urea cycle disorders and liver disease

INTRODUCTION

Ammonia-scavenging drugs, benzoate and phenylacetate (PA)/phenylbutyrate (PB), modulate hepatic nitrogen metabolism mainly by providing alternative pathways for nitrogen disposal. Areas covered: We review the major findings and potential novel applications of ammonia-scavenging drugs, focusing on urea cycle disorders and liver disease. Expert opinion: For over 40 years, ammonia-scavenging drugs have been used in the treatment of urea cycle disorders. Recently, the use of these compounds has been advocated in acute liver failure and cirrhosis for reducing hyperammonemic-induced hepatic encephalopathy. The efficacy and mechanisms underlying the antitumor effects of these ammonia-scavenging drugs in liver cancer are more controversial and are discussed in the review. Overall, as ammonia-scavenging drugs are usually safe and well tolerated among cancer patients, further studies should be instigated to explore the role of these drugs in liver cancer. Considering the relevance of glutamine metabolism to the progression and resolution of liver disease, we propose that ammonia-scavenging drugs might also be used to non-invasively probe liver glutamine metabolism in vivo. Finally, novel derivatives of classical ammonia-scavenging drugs with fewer and less severe adverse effects are currently being developed and used in clinical trials for the treatment of acute liver failure and cirrhosis.

A morphological method for ammonia detection in liver

Hyperammonemia is a metabolic condition characterized by elevated levels of ammonia and a common event in acute liver injury/failure and chronic liver disease. Even though hepatic ammonia levels are potential predictive factors of patient outcome, easy and inexpensive methods aiming at the detection of liver ammonia accumulation in the clinical setting remain unavailable. Thus, herein we have developed a morphological method, based on the utilization of Nessler´s reagent, to accurately and precisely detect the accumulation of ammonia in biological tissue. We have validated our method against a commercially available kit in mouse tissue samples and, by using this modified method, we have confirmed the hepatic accumulation of ammonia in clinical and animal models of acute and chronic advanced liver injury as well as in the progression of fatty liver disease. Overall, we propose a morphological method for ammonia detection in liver that correlates well with the degree of liver disease severity and therefore can be potentially used to predict patient outcome.