Neutrophil Gelatinase-Associated Lipocalin for Assessment of Acute Kidney Injury in Cirrhosis: A Prospective Study

The Liver Intensive Care Unit

Major advances in managing critically ill patients with liver disease have improved their prognosis and access to intensive care facilities. Acute-on-chronic liver failure (ACLF) is now a well-defined disease and these patients can be fast-tracked for liver transplantation (LT) with good outcomes if there are no contraindications. In acute liver failure, plasma exchange has improved prognosis for patients not eligible for immediate transplant. Further advances in novel therapies and refinement of the criteria for early LT in ACLF and also clinical implementation of artificial intelligence tools will probably constitute the next major breakthroughs in critically ill patients with liver disease.

The role of urinary biomarkers in the diagnosis of acute kidney injury in patients with liver cirrhosis

AKI is common in patients with liver cirrhosis (LC) affecting (30 to 50%). Our study aimed to evaluate the role of urinary biomarkers as predictors of AKI, its etiology and mortality. We performed a prospective cohort study of patients with LC during 1 year. Urine samples for biomarkers dosage were collected within 48 h of hospital admission. Diagnosis of AKI was performed according to KDIGO 2012 criteria. The results were presented using Chi-square, T test, AUC-ROC and logistic regression (p < 0.05). We included 100 patients, 58.5 ± 16.1 years, main etiologies of LC were alcohol and and metabolic disfunction associated with steatohepatitis. Infection was the main cause of LC decompensation. AKI occurred in 53% of patients and mortality was 20%. CHILD C, infectious as cause of decompensation, baseline creatinine, need for mechanical ventilation and noradrenaline use and urinary were associated with AKI. We found no association between AKI and KIM-1 and IL-18. The main etiologies of AKI were transient ischeamia (49%), renal (43.4%), and hepatorenal syndrome (HRS) (7.5%). There was difference between the groups in hematuria, proteinuria, FENa, FEUr and uNGAL which were higher in renal AKI when compared to transient ischaemia and HSR. FENa and FEUr were excellent predictors of AKI etiology (AUC-ROC > 0.80, sensitivity and specificity > 0.80), while only uNGAL was good predictor of AKI etiology (AUC-ROC, sensitivity and specificity > 0.70). Regarding death, CHILD C, baseline creatinine, KDIGO 3, septic AKI, need for mechanical ventilation and IL-18 were identified as associated variables. Only NGAL was predictor of AKI and its etiology, anticipating AKI diagnosis in 2.5 ± 1.1 days, while IL-18 was predictor of death. We highlight the importance of lower-cost biochemical tests as FENa and FEUr and clinical information as CHILD and cause of LC descompensation which were relevant in predicting AKI, its etiology and death.

Biliary Metaplasia and Macrophage Activation Define the Cellular Landscape of Cardiogenic Liver Disease

Right heart failure significantly impacts liver remodeling and function, a process referred to as cardiogenic liver disease. Although recognized as a risk factor for adverse outcomes, little is understood about the cellular and molecular players that contribute to liver disease in heart failure. Using human liver biopsy samples from patients with heart failure and a mouse model of liver congestion, we unraveled a nexus of macrophages, hepatic stellate cells, and biliary metaplastic cells that shape the pathologic environment of cardiogenic liver disease.

Acute kidney injury in severe alcohol-associated hepatitis treated with anakinra plus zinc or prednisone

BACKGROUND AND AIMS

In a recent trial, patients with severe alcohol-associated hepatitis treated with anakinra plus zinc (A+Z) had lower survival and higher acute kidney injury (AKI) rates versus prednisone (PRED). We characterize the clinical factors and potential mechanisms associated with AKI development in that trial.

APPROACH AND RESULTS

Data from 147 participants in a multicenter randomized clinical trial (74 A+Z, 73 PRED) were analyzed. AKI, AKI phenotypes, and kidney injury biomarkers were compared between participants who did/did not develop AKI in the 2 treatment arms. Multivariable competing risk analyses were performed to identify baseline risk factors for incident AKI, with death treated as a competing event. Risk factors considered were age, sex, mean arterial pressure, white blood cell count, albumin, MELD, ascites, HE, and treatment arm. At baseline, no participants had AKI; 33% (n=49) developed AKI during follow-up. AKI incidence was higher in A+Z than in PRED (45% [n=33] versus 22% [n=16], p =0.001). AKI phenotypes were similar between the 2 treatment arms ( p =0.361), but peak AKI severity was greater in A+Z than PRED (stage 3 n=21 [63.6%] vs. n=8 [50.0%], p =0.035). At baseline, urine-neutrophil-gelatinase-associated lipocalin levels were similar between participants who developed AKI in both treatment arms ( p =0.319). However, day 7 and 14 urine-neutrophil-gelatinase-associated lipocalin levels were significantly elevated in participants treated with A+Z who developed AKI versus participants treated with PRED who developed AKI ( p =0.002 and 0.032, respectively). On multivariable competing risk analysis, only A+Z was independently associated with incident AKI (subdistribution hazard ratio 2.35, p =0.005).

CONCLUSIONS

AKI occurred more frequently and was more severe in participants treated with A+Z. A+Z-treated participants with AKI had higher urine-neutrophil-gelatinase-associated lipocalin, suggesting that A+Z maybe nephrotoxic in patients with severe alcohol-associated hepatitis.

Noninvasive assessment of hepatic decompensation

Noninvasive tests (NITs) are used in all aspects of liver disease management. Their most prominent break-through since the millennium has been in advancing early detection of liver fibrosis, but their use is not limited to this. In contrast to the symptom-driven assessment of decompensation in patients with cirrhosis, NITs provide not only opportunities for earlier diagnoses but also accurate prognostication, targeted treatment decisions, and a means of monitoring disease. NITs can inform disease management and decision-making based on validated cutoffs and standardized interpretations as a valuable supplement to clinical acumen. The Baveno VI and VII consensus meetings resulted in tangible improvements to pathways of care for patients with compensated and decompensated advanced chronic liver disease, including the combination of platelet count and transient elastography to diagnose clinically significant portal hypertension. Furthermore, circulating NITs will play increasingly important roles in assessing the response to interventions against ascites, variceal bleeding, HE, acute kidney injury, and infections. However, due to NITs' wide availability, there is a risk of inaccurate use, leading to a waste of resources and flawed decisions. In this review, we describe the uses and pitfalls of NITs for hepatic decompensation, from risk stratification in primary care to treatment decisions in outpatient clinics, as well as for the in-hospital management of patients with acute-on-chronic liver failure. We summarize which NITs to use when, for what indications, and how to maximize the potential of NITs for improved patient management.

Management of the acute on chronic liver failure in the intensive care unit

Acute on chronic liver failure (ACLF) reflects the development of organ failure(s) in a patient with cirrhosis and is associated with high short-term mortality. Given that ACLF has many different 'phenotypes', medical management needs to take into account the relationship between precipitating insult, organ systems involved and underlying physiology of chronic liver disease/cirrhosis. The goals of intensive care management of patients suffering ACLF are to rapidly recognize and treat inciting events (e.g. infection, severe alcoholic hepatitis and bleeding) and to aggressively support failing organ systems to ensure that patients may successfully undergo liver transplantation or recovery. Management of these patients is complex since they are prone to develop new organ failures and infectious or bleeding complications. ICU therapy parallels that applied in the general ICU population in some complications but differs in others. Given that liver transplantation in ACLF is an emerging and evolving field, multidisciplinary teams with expertise in critical care and transplant medicine best accomplish management of the critically ill ACLF patient. The focus of this review is to identify the common complications of ACLF and to describe the proper management in critically ill patients awaiting liver transplantation in our centres, including organ support, prognostic assessment and how to assess when recovery is unlikely.

Acute kidney injury stage 1a increases mortality of patients with cirrhosis: a prospective multicenter cohort study

BACKGROUND AND AIMS

Acute kidney injury is a severe complication of cirrhosis. However, the impact of mild decreases in renal function is controversial. This study aims to evaluate the prognosis of the different stages of acute kidney injury in cirrhosis.

METHODS

This is a multicenter prospective cohort study of patients hospitalized for acute decompensation of cirrhosis, with serum creatinine values measured at least twice. Primary outcome was mortality (in-hospital, 30 days, 90 days and 12 months).

RESULTS

Nine hundred twenty-eight patients were included in the study. Acute kidney injury was diagnosed in 505 patients (stages 1a-21.6%, 1b-27.5%, 2-28.1%, 3-22.8%). Mortality rates of patients with acute kidney injury stage 1a were significantly higher than those of individuals without acute kidney injury (in-hospital-19.3% vs 4.7%; 30-day-21.8% vs 6.7%; 90-day-35.2% vs 17.5%; 12-month-54.1% vs 37.1%; p < 0.05 for all comparisons). Mortality rates were even higher for acute kidney injury stages 1b, 2 and 3. Survival analysis demonstrated that patients without acute kidney injury performed significantly better than those with any stage of acute kidney injury (p < 0.01). Acute kidney injury stages 1a, 1b, 2 and 3 were independently associated with survival in the multivariate analysis (p < 0.01).

CONCLUSIONS

Patients hospitalized for acute decompensation of cirrhosis who develop acute kidney injury have significantly higher mortality rates than those who do not develop this complication. This is true even for the mildest stages of acute kidney injury (stage 1a) and remains so at different time-points, supporting recommendations for earlier treatments.

Mortality of Acute Kidney Injury in Cirrhosis: A Systematic Review and Meta-Analysis of Over 5 Million Patients Across Different Clinical Settings

BACKGROUND

Acute kidney injury (AKI) represents a commonly seen condition in the natural course of cirrhosis associated with unfavourable outcomes.

AIMS

To evaluate and compare the pooled mortality rates of patients with cirrhosis, with versus without AKI, across different clinical settings and diagnostic criteria.

METHODS

A systematic search of several databases was performed up to Oct 2023. Meta-analysis was performed using a generalised linear mixed model with a random effects model for all calculations.

RESULTS

A total of 59 studies comparing patients with cirrhosis, with and without AKI, were included in the meta-analysis, encompassing 1,153,193 individuals with AKI and 4,630,814 without AKI. AKI development predisposed to significantly higher short (in-hospital and 30-days)-, intermediate (90-days)- and long (1-year)-term mortality rates in both inpatients and outpatients. Remarkably, patients with AKI admitted to intensive care unit (ICU) or diagnosed with acute-on-chronic liver failure (ACLF) experienced the higher short-term mortality rates, reaching 76% [95% confidence interval (CI): 73%-79%] and 54% (95%CI: 33%-73%), respectively. AKI staging correlated with mortality risk, with higher stages indicating higher mortality rates, while the timing of AKI development, whether community-acquired or hospital-acquired, plays a crucial role in patient prognosis, with distinct mortality patterns observed in each group. The selection of diagnostic criteria for AKI may also impact its association with the short-term mortality risk.

CONCLUSIONS

AKI substantially affects the prognosis of patients with cirrhosis, especially those in ICU and/or with ACLF. Prognosis is also greatly influenced by the AKI stage, timing of onset and diagnostic criteria.

AARC score and urine NGAL predict terlipressin non-response and mortality in patients with acute-on-chronic liver failure

BACKGROUND AND AIM

Acute-on-chronic liver failure (ACLF) patients with hepatorenal syndrome (HRS-AKI) have limited response to vasoconstrictors and worse outcomes, requiring biomarkers for early detection.

METHODS

In a prospective cohort of ACLF patients (n = 240), urine NGAL was performed in patients with the clinical diagnosis of HRS-AKI, while in a subset of patients (n = 30), a complete panel of 17 urinary biomarkers was assessed for identifying terlipressin non-response (T-NR).

RESULTS

ACLF patients with HRS-AKI, aged 45.84 ± 10.6 years, 91.2% males, 74.2% with alcohol etiology, mean urine NGAL of 1541.66 ± 1684.69 ng/ml, AARC score 10.19 ± 1.86, 155 (64.5%) had T-NR at day 4. T-NR was maximal for AARC grade 3 and was associated with a higher need of dialysis (50.3% vs 5.9%; OR 16.21, 6.23-42.19) and 28-day mortality (49.0% vs. 17.9%; HR 3.42, 1.96-5.95). AARC grade 3 (OR 38.21, 2.93-497.74), (HR 5.10, 1.19-21.84) and urine NGAL (OR 11.53, 5.66-23.49; AUROC 0.97, NGAL > 900 ng/ml) (HR 1.23, 1.02-1.49) were independent predictors of T-NR and 28-day mortality, respectively. It was interesting to observe a significant elevation in renal injury and a decrease in the repair markers in T-NR (p < 0.05).

CONCLUSION

Almost 60% of patients with ACLF and HRS-AKI experience non-response to terlipressin which predicts higher mortality and need for dialysis. High NGAL above 900 ng/ml predicts T-NR with 100% specificity for T-NR. ACLF patients with HRS, with AARC grade 3 and high NGAL have a high likelihood of T-NR and should be considered for alternative therapeutic modalities.

Update on Hepatorenal Syndrome: From Pathophysiology to Treatment

Hepatorenal syndrome-acute kidney injury (HRS-AKI) occurs in the setting of advanced chronic liver disease, portal hypertension, and ascites. HRS-AKI is found in ∼20% of patients presenting to the hospital with AKI, but it may coexist with other causes of AKI and/or with preexisting chronic kidney disease, thereby making the diagnosis challenging. Novel biomarkers such as urinary neutrophil gelatinase-associated lipocalin may be useful. While HRS-AKI is a functional form of AKI related to circulatory and neurohormonal dysfunction, there is increasing recognition of the importance of systemic inflammation and the renal microenvironment. Early diagnosis and initiation of HRS-AKI-specific treatment can improve outcomes. The mainstay of therapy is a vasoconstrictor (terlipressin or norepinephrine) combined with albumin, which achieves resolution of HRS in 40-50% of cases. Liver transplantation is the only option for patients failing to respond to medical therapies.

AKI in ACLF: navigating the complex therapeutic puzzle

INTRODUCTION

Acute kidney injury (AKI) in patients with acute-on-chronic liver failure (ACLF) is driven by the severity of systemic inflammation, acute portal hypertension driving circulatory dysfunction, hyperbilirubinemia, and toxicity of bile acids. The spectrum is mostly structural, associated with reduced response to vasoconstrictors. The progression is rapid, and need of renal replacement therapy and extracorporeal therapies may be required for the management. The development of renal failure is usually considered when defining the syndrome of ACLF.

AREAS COVERED

In the current review we discuss the pathophysiological basis, natural course, and response to the current therapeutic modalities and challenges in assessing and managing AKI in patients with ACLF. We conducted a comprehensive search of electronic databases such as PubMed, Web of Science, and Scopus using keywords like lactate, NGAL, and PHTN, as well as CRRT, PLEX, ACLF, and AKI phases for our review. Peer-reviewed English papers that addressed our issue were considered.

EXPERT OPINION

The difficulties and specific management strategies for AKI in ACLF patients are discussed emphasizing the importance of customized protocols, risk assessment guided by biomarkers, and investigation of extracorporeal therapies that target bile acids.

Reliability of neutrophil gelatinase-associated lipocalin in detecting acute tubular necrosis in decompensated cirrhosis: Systematic review and meta-analysis

BACKGROUND

Acute kidney injury (AKI) in cirrhosis is common. The diagnosis of AKI in cirrhosis patients depends on clinical presentation and laboratory tests like serum creatinine. However, urine biomarkers could also be used to assess the type of AKI and the severity of the disease. We performed a systematic review with meta-analysis to evaluate the association with urine neutrophil gelatinase-associated lipocalin (NGAL) marker in identifying acute tubular necrosis (ATN) in patients with cirrhosis.

AIM

To assess the reliability of urine NGAL in the detection of ATN in patients with cirrhosis.

METHODS

We systematically searched MEDLINE and PubMed using keywords including "urine biomarkers", "NGAL", "kidney dysfunction", and "cirrhosis" to identify relevant studies. Data was screened and extracted. Included studies assessed hospitalized cirrhosis patients with AKI using the urine NGAL biomarker. We synthesized the data using diagnostic odds ratio (DOR), comparative and descriptive analyses, and Cochran Mantel-Haenszel (CMH) statistics to evaluate heterogeneity.

RESULTS

Three thousand seven hundred and one patients with cirrhosis were analyzed from a total of 21 cohort studies. The DOR of 14 of those studies [pooled DOR: 22.150, (95%CI: 17.58-27.89), P < 0.0001] demonstrated a significant association between urine NGAL levels and its identification of ATN. Following stratification by cirrhosis status, heterogeneity was analyzed and showed a significant non-zero correlation between NGAL and AKI (CMH statistic = 702.19, P < 0.0001).

CONCLUSION

In patients with cirrhosis, the use of urine NGAL is a reliable biomarker for detecting ATN and identifying the etiology of AKI.

Managing Multiorgan Failure in Acute on Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is defined as a clinical syndrome that develops in patients with chronic liver disease characterized by the presence of organ failure and high short-term mortality, although there is still no worldwide consensus on diagnostic criteria. Management of ACLF is mainly based on treatment of "precipitating factors" (the most common are infections, alcohol-associated hepatitis, hepatitis B flare, and bleeding) and support of organ failure, which often requires admission to the intensive care unit. Liver transplantation should be considered in patients with ACLF grades 2 to 3 as a potentially life-saving treatment. When a transplant is not indicated, palliative care should be considered after 3 to 7 days of full organ support in patients with at least four organ failures or a CLIF-C ACLF score of >70. This review summarizes the current knowledge on the management of organ failure in patients with ACLF, focusing on recent advances.

Prospective validation of the EASL management algorithm for acute kidney injury in cirrhosis

BACKGROUND & AIMS

The management of acute kidney injury (AKI) in cirrhosis is challenging. The EASL guidelines proposed an algorithm for the management of AKI, but this has never been validated. We aimed to prospectively evaluate this algorithm in clinical practice.

METHODS

We performed a prospective cohort study in consecutive hospitalized patients with cirrhosis and AKI. The EASL management algorithm includes identification/treatment of precipitating factors, 2-day albumin infusion in patients with AKI ≥stage 1B, and treatment with terlipressin in patients with hepatorenal syndrome (HRS-AKI). The primary outcome was treatment response, which included both full and partial response. Secondary outcomes were survival and adverse events associated with terlipressin therapy.

RESULTS

A total of 202 AKI episodes in 139 patients were included. Overall treatment response was 80%, while renal replacement therapy was required in only 8%. Response to albumin infusion was achieved in one-third of episodes. Of patients not responding to albumin, most (74%) did not meet the diagnostic criteria of HRS-AKI, with acute tubular necrosis (ATN) being the most common phenotype. The response rate in patients not meeting the criteria for HRS-AKI was 70%. Only 30 patients met the diagnostic criteria for HRS-AKI, and their response rate to terlipressin was 61%. Median time from AKI diagnosis to terlipressin initiation was only 2.5 days. While uNGAL (urinary neutrophil gelatinase-associated lipocalin) could differentiate ATN from other phenotypes (AUROC 0.78), it did not predict response to therapy in HRS-AKI. Ninety-day transplant-free survival was negatively associated with MELD-Na, ATN and HRS-AKI as well as uNGAL. Three patients treated with terlipressin developed pulmonary edema.

CONCLUSIONS

The application of the EASL AKI algorithm is associated with very good response rates and does not significantly delay initiation of terlipressin therapy.

IMPACT AND IMPLICATIONS

The occurrence of acute kidney injury (AKI) in patients with cirrhosis is associated with poor short-term mortality. Improving its rapid identification and prompt management was the focus of the recently proposed EASL AKI algorithm. This is the first prospective study demonstrating that high AKI response rates are achieved with the use of this algorithm, which includes identification of AKI, treatment of precipitating factors, a 2-day albumin challenge in patients with AKI ≥1B, and supportive therapy in patients with persistent AKI not meeting HRS-AKI criteria or terlipressin with albumin in those with HRS-AKI. These findings support the use of this algorithm in clinical practice.

Renal Complications in Portal Hypertension

Acute kidney injury (AKI) is a common complication among patients with decompensated cirrhosis and its development is associated with worse prognosis in terms of survival. Patients with decompensated cirrhosis may develop a unique type of AKI, known as hepatorenal syndrome (HRS-AKI), characterized by marked impairment of kidney function due to haemodynamic changes that occur in late stages of liver cirrhosis. Besides, patients with cirrhosis also may develop chronic alterations of kidney function (chronic kidney disease, CKD), the incidence of which is increasing markedly and may be associated with clinical complications. The aim of this review is to provide the reader with an update of the most relevant aspects of alterations of kidney function in patients with cirrhossi that may be useful for theri clinical practice.

Acute kidney injury in patients with cirrhosis: Acute Disease Quality Initiative (ADQI) and International Club of Ascites (ICA) joint multidisciplinary consensus meeting

Patients with cirrhosis are prone to developing acute kidney injury (AKI), a complication associated with a markedly increased in-hospital morbidity and mortality, along with a risk of progression to chronic kidney disease. Whereas patients with cirrhosis are at increased risk of developing any phenotype of AKI, hepatorenal syndrome (HRS), a specific form of AKI (HRS-AKI) in patients with advanced cirrhosis and ascites, carries an especially high mortality risk. Early recognition of HRS-AKI is crucial since administration of splanchnic vasoconstrictors may reverse the AKI and serve as a bridge to liver transplantation, the only curative option. In 2023, a joint meeting of the International Club of Ascites (ICA) and the Acute Disease Quality Initiative (ADQI) was convened to develop new diagnostic criteria for HRS-AKI, to provide graded recommendations for the work-up, management and post-discharge follow-up of patients with cirrhosis and AKI, and to highlight priorities for further research.

APASL clinical practice guidelines on the management of acute kidney injury in acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) is a syndrome that is characterized by the rapid development of organ failures predisposing these patients to a high risk of short-term early death. The main causes of organ failure in these patients are bacterial infections and systemic inflammation, both of which can be severe. For the majority of these patients, a prompt liver transplant is still the only effective course of treatment. Kidneys are one of the most frequent extrahepatic organs that are affected in patients with ACLF, since acute kidney injury (AKI) is reported in 22.8-34% of patients with ACLF. Approach and management of kidney injury could improve overall outcomes in these patients. Importantly, patients with ACLF more frequently have stage 3 AKI with a low rate of response to the current treatment modalities. The objective of the present position paper is to critically review and analyze the published data on AKI in ACLF, evolve a consensus, and provide recommendations for early diagnosis, pathophysiology, prevention, and management of AKI in patients with ACLF. In the absence of direct evidence, we propose expert opinions for guidance in managing AKI in this very challenging group of patients and focus on areas of future research. This consensus will be of major importance to all hepatologists, liver transplant surgeons, and intensivists across the globe.

Acute kidney injury and point-of-care ultrasound in liver cirrhosis: redefining hepatorenal syndrome

Acute kidney injury (AKI) in patients with cirrhosis is a diagnostic challenge due to multiple and sometimes overlapping possible etiologies. Many times, diagnosis cannot be made based on case history, physical examination or laboratory data, especially when the nephrologist is faced with AKI with a hemodynamic basis, such as hepatorenal syndrome. In addition, the guidelines still include generalized recommendations regarding withdrawal of diuretics and plasma volume expansion with albumin for 48 h, which may be ineffective and counterproductive and may have iatrogenic effects, such as fluid overload and acute cardiogenic pulmonary edema. For this reason, the use of new tools, such as hemodynamic point-of-care ultrasound (PoCUS), allows us to phenotype volume status more accurately and ultimately guide medical treatment in a noninvasive, rapid and individualized manner.

Hepatorenal Syndrome in Cirrhosis

Hepatorenal syndrome (HRS) is a form of kidney dysfunction that characteristically occurs in liver cirrhosis. It is characterized by a marked impairment of kidney function in response to circulatory and hemodynamic alterations that occur in advanced stages of liver cirrhosis, aggravated by systemic inflammation and bacterial translocation. The classical definitions of the types of HRS have been recently revisited and 2 forms of HRS have been redefined: the acute form, referred to as acute kidney injury (HRS-AKI), and the chronic form, referred to as chronic kidney disease. HRS-AKI is one of the most severe forms of AKI in patients with cirrhosis and it consists of an abrupt impairment of kidney function, frequently triggered by an infection, appearing in the setting of advanced decompensated cirrhosis. Differential diagnosis with other causes of AKI is crucial because HRS-AKI requires a specific treatment. Differential diagnosis with AKI-acute tubular necrosis may be challenging and kidney biomarkers may be useful in this setting. Treatment of HRS-AKI is based on the administration of vasoconstrictor drugs in combination with volume expansion with albumin. Prognosis of HRS-AKI is poor, and the ideal definitive treatment consists of liver transplantation or simultaneous liver-kidney transplantation. HRS-AKI has a big impact on patients' quality of life. Management of HRS-AKI remains challenging in specific situations such as alcohol-associated hepatitis or metabolic-associated steatotic liver disease cirrhosis. Developing preventive measures for HRS-AKI, improving its early identification, discovering new biomarkers for differential diagnosis, and improving the response to therapy are some of the unmet needs in the field of HRS-AKI.

Hepatorenal Syndrome Type 1: Diagnosis and Treatment

Hepatorenal syndrome (HRS) is a feared complication in patients with advanced cirrhosis and is associated with significant morbidity and mortality. While recognized as a distinct physiologic condition for well over one hundred years, a lack of objective diagnostic tests has made the diagnosis one of exclusion. Since 1979, multiple sets of diagnostic criteria have been proposed. Though varying in detail, the principal intent of these criteria is to identify patients with severe, functional acute kidney injury that is unresponsive to volume resuscitation and exclude those with structural injury. However, accurate differential diagnosis remains challenging. Recently, multiple urinary biomarkers of kidney injury, including neutrophil gelatinase-associated lipocalin, have been studied as a means of objectively phenotyping etiologies of acute kidney injury in patients with cirrhosis. Along with markers reflecting tubular functional integrity, including the fractional excretion of sodium, injury markers will likely be incorporated into future diagnostic criteria. Making an accurate diagnosis is critical, as therapeutic options exist for HRS but must be given in a timely manner and only to those patients likely to benefit. Terlipressin, an analog of vasopressin, is the first line of therapy for HRS in much of the world and has recently been approved for use in the United States. Significant questions remain regarding the optimal dosing strategy, metrics for titration, and the potential role of point-of-care ultrasound to help guide concurrent albumin administration.

From past to present to future: Terlipressin and hepatorenal syndrome-acute kidney injury

Hepatorenal syndrome (HRS) is a rare and highly morbid form of kidney injury unique to patients with decompensated cirrhosis. HRS is a physiologic consequence of portal hypertension, leading to a functional kidney injury that can be reversed by restoring effective circulating volume and renal perfusion. While liver transplantation is the only definitive "cure" for HRS, medical management with vasoconstrictors and i.v. albumin is a cornerstone of supportive care. Terlipressin, a V1a receptor agonist that acts on the splanchnic circulation, has been used for many years outside the United States for the treatment of HRS. However, its recent Food and Drug Administration approval has generated new interest in this population, as a new base of prescribers now work to incorporate the drug into clinical practice. In this article, we review HRS pathophysiology and diagnostic criteria, the clinical use of terlipressin and alternative therapies, and identify areas of future research in the space of HRS and kidney injury in cirrhosis.

Toward Precision Medicine: Exploring the Landscape of Biomarkers in Acute Kidney Injury

Acute kidney injury (AKI) remains a complex challenge with diverse underlying pathological mechanisms and etiologies. Current detection methods predominantly rely on serum creatinine, which exhibits substantial limitations in specificity and poses the issue of late-stage detection of kidney injury. In this review, we propose an up-to-date and comprehensive summary of advancements that identified novel biomarker candidates in blood and urine and ideal criteria for AKI biomarkers such as renal injury specificity, mechanistic insight, prognostic capacity, and affordability. Recently identified biomarkers not only indicate injury location but also offer valuable insights into a range of pathological processes, encompassing reduced glomerular filtration rate, tubular function, inflammation, and adaptive response to injury. The clinical applications of AKI biomarkers are becoming extensive and serving as relevant tools in distinguishing acute tubular necrosis from other acute renal conditions. Also, these biomarkers can offer significant insights into the risk of progression to chronic kidney disease CKD and in the context of kidney transplantation. Integration of these biomarkers into clinical practice has the potential to improve early diagnosis of AKI and revolutionize the design of clinical trials, offering valuable endpoints for therapeutic interventions and enhancing patient care and outcomes.

AGA Clinical Practice Update on the Use of Vasoactive Drugs and Intravenous Albumin in Cirrhosis: Expert Review

DESCRIPTION

Cirrhosis is a major cause of morbidity and mortality in the United States and worldwide. It consists of compensated, decompensated, and further decompensated stages; median survival is more than 15 years, 2 years, and 9 months for each stage, respectively. With each stage, there is progressive worsening of portal hypertension and the vasodilatory-hyperdynamic circulatory state, resulting in a progressive decrease in effective arterial blood volume and renal perfusion. Vasoconstrictors reduce portal pressure via splanchnic vasoconstriction and are used in the management of variceal hemorrhage. Intravenous (IV) albumin increases effective arterial blood volume and is used in the prevention of acute kidney injury (AKI) and death after large-volume paracentesis and in patients with spontaneous bacterial peritonitis (SBP). The combination of vasoconstrictors and albumin is used in the reversal of hepatorenal syndrome (HRS-AKI), the most lethal complication of cirrhosis. Because a potent vasoconstrictor, terlipressin, was recently approved by the US Food and Drug Administration, and because recent trials have explored use of IV albumin in other settings, it was considered that a best practice update would be relevant regarding the use of vasoactive drugs and IV albumin in the following 3 specific scenarios: variceal hemorrhage, ascites and SBP, and HRS.

METHODS

This expert review was commissioned and approved by the American Gastroenterological Association (AGA) Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership. It underwent internal peer review through standard procedures of Gastroenterology. These Best Practice Advice statements were drawn from a review of the published literature and from expert opinion. Some of the statements are unchanged from published guidelines because of lack of new evidence in the literature. Because systematic reviews were not performed, these Best Practice Advice statements do not carry formal ratings regarding the quality and evidence or strength of the presented considerations. Best Practice Advice Statements BEST PRACTICE ADVICE 1: Vasoactive drugs should be initiated as soon as the diagnosis of variceal hemorrhage is suspected or confirmed, preferably before diagnostic and/or therapeutic endoscopy. BEST PRACTICE ADVICE 2: After initial endoscopic hemostasis, vasoactive drugs should be continued for 2-5 days to prevent early rebleeding. BEST PRACTICE ADVICE 3: Octreotide is the vasoactive drug of choice in the management of variceal hemorrhage based on its safety profile. BEST PRACTICE ADVICE 4: IV albumin should be administered at the time of large-volume (>5 L) paracentesis. BEST PRACTICE ADVICE 5: IV albumin may be considered in patients with SBP. BEST PRACTICE ADVICE 6: Albumin should not be used in patients (hospitalized or not) with cirrhosis and uncomplicated ascites. BEST PRACTICE ADVICE 7: Vasoconstrictors should not be used in the management of uncomplicated ascites, after large-volume paracentesis or in patients with SBP. BEST PRACTICE ADVICE 8: IV albumin is the volume expander of choice in hospitalized patients with cirrhosis and ascites presenting with AKI. BEST PRACTICE ADVICE 9: Vasoactive drugs (eg, terlipressin, norepinephrine, and combination of octreotide and midodrine) should be used in the treatment of HRS-AKI, but not in other forms of AKI in cirrhosis. BEST PRACTICE ADVICE 10: Terlipressin is the vasoactive drug of choice in the treatment of HRS-AKI and use of concurrent albumin can be considered when accounting for patient's volume status. BEST PRACTICE ADVICE 11: Terlipressin treatment does not require intensive care unit monitoring and can be administered intravenously through a peripheral line. BEST PRACTICE ADVICE 12: Terlipressin use is contraindicated in patients with hypoxemia and in patients with ongoing coronary, peripheral, or mesenteric ischemia, and should be used with caution in patients with acute-on-chronic liver failure grade 3. The benefits may not outweigh the risks in patients with serum creatinine >5 mg/dL and in patients listed for transplantation with a Model for End-stage Liver Disease ≥35.

Novel prognostic biomarkers in decompensated cirrhosis: a systematic review and meta-analysis

BACKGROUND

Patients with decompensated cirrhosis experience high mortality rates. Current prognostic scores, including the model for end-stage liver disease (MELD), may underperform in settings other than in those they were initially developed. Novel biomarkers have been proposed to improve prognostication accuracy and even to predict development of complications.

METHODS

We performed a systematic review and meta-analysis on novel urine and blood biomarkers and their ability to predict 90-day mortality in patients with decompensated cirrhosis. Secondary outcomes included 28-day and 1-year mortality, and development of acute-on-chronic liver failure, acute kidney injury and other complications. To overcome differences in units, temporal changes in assays and reporting heterogeneity, we used the ratio of means (RoM) as measure of association for assessing strength in predicting outcomes. An RoM>1 implies that the mean biomarker level is higher in those that develop the outcome than in those that do not.

RESULTS

Of 6629 unique references, 103 were included, reporting on 29 different biomarkers, with a total of 31 362 biomarker patients. Most studies were prospective cohorts of hospitalised patients (median Child-Pugh-Turcotte score of 9 and MELD score of 18). The pooled 90-day mortality rate was 0.27 (95% CI 0.24 to 0.29). The RoM for predicting 90-day mortality was highest for interleukin 6 (IL-6) (2.56, 95% CI 2.39 to 2.74), followed by urinary neutrophil gelatinase-associated lipocalin (uNGAL) (2.42, 95% CI 2.20 to 2.66) and copeptin (2.33, 95% CI 2.17 to 2.50). These RoMs were all higher than for MELD (1.44, 95% CI 1.42 to 1.46).

CONCLUSION

Novel biomarkers, including IL-6, uNGAL and copeptin, can probably improve prognostication of patients with decompensated cirrhosis compared with MELD alone.

Securing the diagnosis of HRS-AKI: implications for current therapies

INTRODUCTION

Hepatorenal syndrome (HRS)-acute kidney injury (HRS-AKI) is a specific type of kidney injury seen in patients with cirrhosis and ascites and is associated with high mortality and morbidity. It is characterized by rapid deterioration of renal function due to reduced renal blood flow secondary to portal hypertensive splanchnic and systemic vasodilation. Early diagnosis and treatment of HRS-AKI are associated with greater likelihood of improvement in renal function, lower need for dialysis, and better post-transplant outcomes.

AREAS COVERED

This review discusses the diagnostic criteria for HRS-AKI, which has undergone several key changes over the last decade, with an aim to secure an early diagnosis and aid swift treatment initiation. Additionally, this review outlines the current treatment paradigms for HRS-AKI.

EXPERT OPINION

In the last 20 years, there have been several advances in understanding the pathophysiology and natural course of HRS-AKI. These have led to critical changes in its definition and diagnostic algorithm. However, prognosis of HRS-AKI remains dismal with no significant improvement in HRS-AKI reversal or HRS-related mortality over this time. We discuss several gaps in the current understanding and management of HRS-AKI that will benefit from further research.

Incidence and outcomes of acute kidney injury including hepatorenal syndrome in hospitalized patients with cirrhosis in the US

BACKGROUND & AIMS

Acute kidney injury (AKI) in cirrhosis is common and associated with high morbidity, but the incidence rates of different etiologies of AKI are not well described in the US. We compared incidence rates, practice patterns, and outcomes across etiologies of AKI in cirrhosis.

METHODS

We performed a retrospective cohort study of 11 hospital networks, including consecutive adult patients admitted with AKI and cirrhosis in 2019. The etiology of AKI was adjudicated based on pre-specified clinical definitions (prerenal/hypovolemic AKI, hepatorenal syndrome [HRS-AKI], acute tubular necrosis [ATN], other).

RESULTS

A total of 2,063 patients were included (median age 62 [IQR 54-69] years, 38.3% female, median MELD-Na score 26 [19-31]). The most common etiology was prerenal AKI (44.3%), followed by ATN (30.4%) and HRS-AKI (12.1%); 6.0% had other AKI, and 7.2% could not be classified. In our cohort, 8.1% of patients received a liver transplant and 36.5% died by 90 days. The lowest rate of death was observed in patients with prerenal AKI (22.2%; p <0.001), while death rates were higher but not significantly different from each other in those with HRS-AKI and ATN (49.0% vs. 52.7%; p = 0.42). Using prerenal AKI as a reference, the adjusted subdistribution hazard ratio (sHR) for 90-day mortality was higher for HRS-AKI (sHR 2.78; 95% CI 2.18-3.54; p <0.001) and ATN (sHR 2.83; 95% CI 2.36-3.41; p <0.001). In adjusted analysis, higher AKI stage and lack of complete response to treatment were associated with an increased risk of 90-day mortality (p <0.001 for all).

CONCLUSION

AKI is a severe complication of cirrhosis. HRS-AKI is uncommon and is associated with similar outcomes to ATN. The etiology of AKI, AKI stage/severity, and non-response to treatment were associated with mortality. Further optimization of vasoconstrictors for HRS-AKI and supportive therapies for ATN are needed.

IMPACT AND IMPLICATIONS

Acute kidney injury (AKI) in cirrhosis carries high morbidity, and management is determined by the etiology of injury. However, a large and well-adjudicated multicenter database from US centers that uses updated AKI definitions is lacking. Our findings demonstrate that acute tubular necrosis and hepatorenal syndrome have similar outcomes (∼50% mortality at 90 days), though hepatorenal syndrome is uncommon (12% of all AKI cases). These findings represent practice patterns at US transplant/tertiary centers and can be used as a baseline, presenting the situation prior to the adoption of terlipressin in the US.

[Hepatorenal Syndrome]

Hepatorenal syndrome (HRS) is a critical and potentially life-threatening complication of advanced liver disease, including cirrhosis. It is characterized by the development of renal dysfunction in the absence of underlying structural kidney pathology. The pathophysiology of HRS involves complex interactions between systemic and renal hemodynamics, neurohormonal imbalances, and the intricate role of vasoconstrictor substances. Understanding these mechanisms is crucial for the timely identification and management of HRS. The diagnosis of HRS is primarily clinical and relies on specific criteria that consider the exclusion of other causes of renal dysfunction. The management of HRS comprises two main approaches: vasoconstrictor therapy and albumin infusion, which aim to improve renal perfusion and mitigate the hyperdynamic circulation often seen in advanced liver disease. Additionally, strategies such as liver transplantation and renal replacement therapy are essential considerations based on individual patient characteristics and disease severity. This review article provides a comprehensive overview of hepatorenal syndrome, focusing on its pathophysiology, diagnostic criteria, and current management strategies.

Diagnostic value of combined detection of urine NGAL, KIM-1, and TFF3 in acute tubular necrosis associated with cirrhosis

BACKGROUND

Acute kidney injury (AKI) is a common complication of decompensated cirrhosis with high clinical mortality and poor prognosis, of which acute tubular necrosis (ATN) has the worst prognosis. Timely and accurate identification of ATN is a difficult problem to solve clinically. Previous studies have shown that urinary neutrophil gelatinase-associated lipocalin (NGAL), trefoil factor 3 (TFF3), and kidney injury molecule-1 (KIM-1) have potential value in the differential diagnosis of ATN and other types of AKI in patients with liver cirrhosis, but they still cannot be applied in clinical practice due to the low diagnostic efficacy. It is necessary to further explore whether the combined detection of the indicators can improve their diagnostic efficacy for ATN associated with cirrhosis.

AIM

To analyze the value of urinary NGAL, KIM-1, and TFF3, either alone or in combination, in the differential diagnosis of ATN in patients with cirrhosis complicated with AKI, and explore the cut-off values of urinary NGAL and other indicators in the differential diagnosis of ATN.

METHODS

A total of 190 patients with decompensated cirrhosis were selected, including 108 patients with AKI. They were divided into different subgroups according to the cause of AKI, including 33 cases of prerenal azotemia, 27 cases of acute renal injury with hepatorenal syndrome, and 48 cases of ATN. The value of urinary NGAL, TFF3, and KIM-1, either alone or in combination, in the differential diagnosis of ATN in patients with cirrhosis complicated with AKI was then assessed.

RESULTS

Urinary NGAL was of great value in the differential diagnosis of ATN in patients with cirrhosis complicated with AKI. The area under the curve (AUC) was 0.902; when the diagnostic threshold was 271.8 μg/g Cr, the sensitivity was 81.3% and the specificity was 85.0%. The combination of two biomarkers could improve the efficacy of differential diagnosis, with the diagnostic perfomance of urinary NGAL combined with urinary TFF3 being the best (AUC = 0.933, sensitivity 85.4%, specificity 88.3%).

CONCLUSION

Urinary NGAL, KIM-1, and TFF3 are of great value in differentiating ATN from other types of AKI in patients with cirrhosis. The combined detection of any two of these biomarkers can further improve the diagnostic efficiency, which is worthy of further study and clinical promotion.

Hepatorenal syndrome: Current concepts and future perspectives

Hepatorenal syndrome (HRS), a progressive but potentially reversible deterioration of kidney function, remains a major complication in patients with advanced cirrhosis, often leading to death before liver transplantation (LT). Recent updates in the pathophysiology, definition, and classification of HRS have led to a complete revision of the nomenclature and diagnostic criteria for HRS type 1, which was renamed HRS-acute kidney injury (AKI). HRS is characterized by severe impairment of kidney function due to increased splanchnic blood flow, activation of several vasoconstriction factors, severe vasoconstriction of the renal arteries in the absence of kidney histologic abnormalities, nitric oxide dysfunction, and systemic inflammation. Diagnosis of HRS remains a challenge because of the lack of specific diagnostic biomarkers that accurately distinguishes structural from functional AKI, and mainly involves the differential diagnosis from other forms of AKI, particularly acute tubular necrosis. The optimal treatment of HRS is LT. While awaiting LT, treatment options include vasoconstrictor drugs to counteract splanchnic arterial vasodilation and plasma volume expansion by intravenous albumin infusion. In patients with HRS unresponsive to pharmacological treatment and with conventional indications for kidney replacement therapy (KRT), such as volume overload, uremia, or electrolyte imbalances, KRT may be applied as a bridging therapy to transplantation. Other interventions, such as transjugular intrahepatic portosystemic shunt, and artificial liver support systems have a very limited role in improving outcomes in HRS. Although recently developed novel therapies have potential to improve outcomes of patients with HRS, further studies are warranted to validate the efficacy of these novel agents.

Diagnostic utility of urine neutrophil gelatinase-associated lipocalin and renal resistive index in patients of decompensated cirrhosis with acute kidney injury

BACKGROUND

The differentiation between types of acute kidney injury(AKI) in decompensated cirrhosis(DC) patients in clinical practice is done by clinical adjudication. Biomarkers have good diagnostic accuracy for predicting acute tubular necrosis(ATN), however they are not available routinely.

AIMS

We compared the diagnostic accuracy of urine neutrophil gelatinase-associated lipocalin(UNGAL) and renal resistive index(RRI) in predicting type of AKI among DC patients.

METHODS

Consecutive DC patients with AKI stage≥1B seen between June/2020 to May/2021 were evaluated. UNGAL levels and RRI were measured at diagnosis of AKI(Day 0) and 48hrs(Day 3) after volume expansion. Diagnostic accuracy of UGNAL and RRI was compared for differentiating ATN and non-ATN AKI by area under receiver operating characteristic curve(AUROC), using clinical adjudication as gold standard.

RESULTS

388 DC patients were screened, 86 patients(Pre-renal AKI[PRA] n=47,55%; Hepatorenal syndrome[HRS] n=25,29%;ATN n= 14,16%) were included. The AUROC of UNGAL for differentiating ATN-AKI and non-ATN AKI at day 0 was 0.97(95%CI, 0.95-1.0) and on day 3 was 0.97(95%CI, 0.94-1.0). The AUROC of RRI for differentiating ATN and non-ATN AKI at day 0 was 0.68(95%CI, 0.55-0.80) and on day 3 was 0.74(95%CI, 0.63-0.84).

CONCLUSION

UNGAL has an excellent diagnostic accuracy in predicting ATN-AKI in DC patients both at day 0 and 3.

Non-resolution of acute kidney injury in the first week portends the development of chronic kidney disease in critically ill patients with cirrhosis

BACKGROUND

Renal tubular epithelial cells (RTECs) cause maladaptive repair and perpetuate renal fibrosis.

AIM

To evaluate urinary neutrophil gelatinase-associated lipocalin (NGAL) and RTEC as risk factors for non-resolution of acute kidney injury (AKI-NR) at day seven and chronic kidney disease (CKD) in critically ill patients with cirrhosis.

METHODS

We performed urinary NGAL and microscopy at enrolment and day 7 in all patients. We assessed 17 renal injury, endothelial injury and repair markers, genes for mitochondrial biogenesis by qRT-PCR in RTEC, and post-mortem renal biopsies for understanding mechanisms of AKI non-resolution (n = 30).

RESULTS

We enrolled 310 patients, aged 48.1 ± 11.6 years, 87% male, 90% alcoholic. Of these, 36% had RTEC at enrolment, and 53% had AKI-NR on day 7. On mean follow-up of 136 days (range 43-365), 150 (48.3%) developed CKD. The presence of RTEC or granular casts, NGAL and AKI-NR were independent predictors of CKD development on competing risk analysis. Higher MCP-1, renal endothelial injury, decrease in tubular repair markers and failure of mitochondrial biogenesis in RTEC were seen in patients with AKI-NR compared with AKI-R (p < 0.05). Renal biopsies showed infiltration with monocyte-macrophage, increased α-SMA, and tubulointerstitial fibrosis.

CONCLUSION

Almost two-thirds of critically ill patients with cirrhosis have AKI, which resolves in only one-half at day seven and predicts the development of CKD. Higher NGAL, RTEC, or granular casts were independent predictors of AKI-NR and CKD development. Enhanced tubular and endothelial injury, decreased repair, monocyte-macrophage infiltration and mitochondrial dysfunction in RTEC are associated with AKI non-resolution and risk of renal fibrosis.

The Diagnosis and Non-pharmacological Management of Acute Kidney Injury in Patients with Cirrhosis

Acute kidney injury in patients with cirrhosis is quite common, and is seen in up to 50% of patients hospitalized for decompensated cirrhosis. Causes of acute kidney injury include prerenal, renal, or postrenal etiologies. The diagnosis and early institution of nonpharmacologic and pharmacologic management are key to the recovery of renal function. The objective of this review is to provide a practical approach to the use of diagnostic biomarkers and highlight the nonpharmacologic management and prevention of acute kidney injury.

Precision management of acute kidney injury in the intensive care unit: current state of the art

Acute kidney injury (AKI) is a prototypical example of a common syndrome in critical illness defined by consensus. The consensus definition for AKI, traditionally defined using only serum creatinine and urine output, was needed to standardize the description for epidemiology and to harmonize eligibility for clinical trials. However, AKI is not a simple disease, but rather a complex and multi-factorial syndrome characterized by a wide spectrum of pathobiology. AKI is now recognized to be comprised of numerous sub-phenotypes that can be discriminated through shared features such as etiology, prognosis, or common pathobiological mechanisms of injury and damage. The characterization of sub-phenotypes can serve to enable prognostic enrichment (i.e., identify subsets of patients more likely to share an outcome of interest) and predictive enrichment (identify subsets of patients more likely to respond favorably to a given therapy). Existing and emerging biomarkers will aid in discriminating sub-phenotypes of AKI, facilitate expansion of diagnostic criteria, and be leveraged to realize personalized approaches to management, particularly for recognizing treatment-responsive mechanisms (i.e., endotypes) and targets for intervention (i.e., treatable traits). Specific biomarkers (e.g., serum renin; olfactomedin 4 (OLFM4); interleukin (IL)-9) may further enable identification of pathobiological mechanisms to serve as treatment targets. However, even non-specific biomarkers of kidney injury (e.g., neutrophil gelatinase-associated lipocalin, NGAL; [tissue inhibitor of metalloproteinases 2, TIMP2]·[insulin like growth factor binding protein 7, IGFBP7]; kidney injury molecule 1, KIM-1) can direct greater precision management for specific sub-phenotypes of AKI. This review will summarize these evolving concepts and recent innovations in precision medicine approaches to the syndrome of AKI in critical illness, along with providing examples of how they can be leveraged to guide patient care.

Role of urine/serum NGAL ratio in differential diagnosis of acute kidney injury in patients with cirrhosis

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) can be used for the differential diagnosis of acute kidney necrosis (ATN) and other types of acute kidney injury (AKI) in patients with liver cirrhosis complicated with AKI. However, serum NGAL is directly related to urine NGAL, and there are few existing studies on the role of urine /serum NGAL ratio in the differential diagnosis of ATN.

AIM

To assess the significance of serum and urine NGAL as well as urine/serum NGAL ratio in differentiating ATN from other types of AKI in cirrhosis.

METHODS

A total of 180 patients with decompensated cirrhosis were included in the study, of whom 98 were complicated with AKI. According to the etiology of AKI, there were 33 patients with prerenal azotemia, 25 with hepatorenal syndrome-AKI, and 40 with ATN. The patients were divided into different subgroups to assess the value of NGAL in differentiating the types of AKI.

RESULTS

Urine NGAL and urine/serum NGAL ratio showed signi-ficant value in the differential diagnosis of ATN in patients with liver cirrhosis. At an optimal cut-off of 271.35 ng/mL, urine NGAL distinguished ATN from other types of AKI (area under the cuve [AUC] = 0.964; sensitivity, 87.5%; specificity, 96.6%). As well, at an optimal cut-off of 2.96, urine/serum NGAL ratio could also distinguish ATN from other types of AKI (AUC = 0.953, sensitivity 92.5% and specificity 91.4%).

CONCLUSION

Urine NGAL and urine/serum NGAL ratio have significant value in the differential diagnosis of ATN and other types of AKI in patients with liver cirrhosis, which is worthy of further study and clinical promotion.

Renal damage in Hepatorenal Syndrome: A still unsolved issue

Acute kidney injury (AKI) is a common complication of cirrhosis, burdened by high morbidity and mortality rates and progression to chronic kidney disease. Hepatorenal syndrome (HRS) is a peculiar type of functional AKI observed in cirrhotic patients with ascites. HRS diagnosis is still clinical, once pre-renal azotemia and intrinsic kidney damage have been excluded by applying well-established and internationally adopted criteria. HRS is considered reversible because of the absence of intrinsic renal damage. However, HRS reversibility has been questioned, due to the lack of response to treatment with vasoconstrictors plus albumin in a relevant percentage of patients and to the persistence of renal dysfunction in HRS patients who underwent liver transplantation (LT). Indeed, LT is the only ultimate treatment, as it solves both liver failure and portal hypertension. Thus, the presence of renal damage in HRS can be hypothesized. In this scenario, neutrophil gelatinase-associated lipocalin (NGAL), one of the most promising biomarkers, may help in characterizing the type of renal injury, distinguishing between HRS and acute tubular necrosis. This review gathers the available evidence in favor and against the presence of structural lesions in HRS in terms of either renal histology and urinary biomarkers with a particular focus on NGAL. The ability to properly characterize which component of renal dysfunction prevails - functional rather than structural - entails a relevant clinical impact for the treatment of these patients, both in terms of medical therapy and liver vs. combined liver-kidney transplantation.

Urinary Neutrophil Gelatinase-associated Lipocalin as a Diagnostic and Prognostic Marker for Acute Kidney Injury in Hospitalized Cirrhotic Patients: A Study from North Indian Population

Background

A serious problem in cirrhosis is acute renal injury. The study aimed to examine the urinary neutrophil gelatinase-associated lipocalin (uNGAL) as a diagnostic and prognostic marker of acute kidney injury (AKI) in cirrhotic patients.

Methods

A prospective study was carried out over a period of 1 year. A total of 490 patients suffering from cirrhosis who visited an indoor hospital were screened, and after the exclusion, a total of 90 subjects admitted to the medicine intensive care unit (MICU) fulfilling inclusion criteria were enrolled. Those having a history of renal diseases, on nephrotoxic drugs, in septic shock, peritonitis, UTI, and no urine output were excluded. On admission, for the estimation of uNGAL, urinary levels of sodium, creatinine, fresh urine samples were obtained, and blood samples were taken for serum creatinine estimation.

Results

Out of 90 patients, 33.3% did not develop AKI, and 66.7% developed AKI. Urinary neutrophil gelatinase-associated lipocalin levels were six times higher in patients with acute tubular necrosis (259.08 ± 118.41 ng/mL) and three times higher in Hepatorenal syndrome (HRS)-AKI (124.97 ± 16.38) as compared with patients with normal kidney function (39.76 + 5.7). Those who died had a higher uNGAL (171.6 ng/mL) in comparison to those who survived (133.7 ng/mL). At a cutoff value of ≥114.9 (ng/mL), urinary NGAL represents a sensitivity of 86.92% and specificity of 100% to diagnose AKI and AUC 0.966 (95% CI: 0.919-0.990) in cirrhotic patients.

Conclusion

Urinary NGAL is good for diagnosing AKI and is a marker to distinguish the types of AKI in liver cirrhosis.

How to cite this article

Patel ML, Shyam R, Chaudhary A, Sachan R, Ali W. Urinary Neutrophil Gelatinase-associated Lipocalin as a Diagnostic and Prognostic Marker for Acute Kidney Injury in Hospitalized Cirrhotic Patients: A Study from North Indian Population. Indian J Crit Care Med 2023;27(8):545-551.

Acute Kidney Injury in Liver Cirrhosis

Acute kidney injury (AKI) is common in cirrhotic patients affecting almost 20% of these patients. While multiple etiologies can lead to AKI, pre-renal azotemia seems to be the most common cause of AKI. Irrespective of the cause, AKI is associated with worse survival with the poorest outcomes observed in those with hepatorenal syndrome (HRS) and acute tubular necrosis (ATN). In recent years, new definitions, and classifications of AKI in cirrhosis have emerged. More knowledge has also become available regarding the benefits and drawbacks of albumin and terlipressin use in these patients. Diagnostic tools such as urinary biomarkers and point-of-care ultrasound (POCUS) became available and they will be used in the near future to differentiate between different causes of AKI and direct management of AKI in these patients. In this update, we will review these new classifications, treatment recommendations, and diagnostic tools for AKI in cirrhotic patients.

Hepatorenal Syndrome: Pathophysiology, Diagnosis, and Treatment

Hepatorenal syndrome (HRS) is a primarily functional form of acute kidney injury (AKI) that develops in patients with decompensated cirrhosis. The pathophysiologic cascade that leads to HRS begins with pooling of blood in the splanchnic system, resulting in a decrease in effective circulating arterial volume. The definitive treatment of HRS is liver transplantation. When this is not possible, HRS is treated with a combination of vasoconstrictor agents and intravenous albumin. Although the combination of midodrine and octreotide is used in the United States, the recently approved terlipressin, an analog of vasopressin, is likely to become the first-line standard of care.

Recent advances in pathophysiology, diagnosis and management of hepatorenal syndrome: A review

Hepatorenal syndrome with acute kidney injury (HRS-AKI) is a form of rapidly progressive kidney dysfunction in patients with decompensated cirrhosis and/or acute severe liver injury such as acute liver failure. Current data suggest that HRS-AKI occurs secondary to circulatory dysfunction characterized by marked splanchnic vasodilation, leading to reduction of effective arterial blood volume and glomerular filtration rate. Thus, volume expansion and splanchnic vasoconstriction constitute the mainstay of medical therapy. However, a significant proportion of patients do not respond to medical management. These patients often require renal replacement therapy and may be eligible for liver or combined liver-kidney transplantation. Although there have been advances in the management of patients with HRS-AKI including novel biomarkers and medications, better-calibrated studies, more widely available biomarkers, and improved prognostic models are sorely needed to further improve diagnosis and treatment of HRS-AKI.

Kidney disease in patients with chronic liver disease: Does sex matter?

Kidney disease in patients with liver disease is serious and increases mortality. Up to 50% of patients hospitalized experience an episode of acute kidney injury. In general, men with liver disease are thought to be at increased risk of kidney disease. However, this association should be considered with caution because most studies use creatinine-based inclusion criteria, which is negatively biased against women. In this review, we synthesize data on sex differences in kidney disease in patients with chronic liver disease in the clinical setting and discuss potential physiologic underpinnings.

Diagnostic and prognostic performance of urinary neutrophil gelatinase-associated lipocalin in patients with cirrhosis and acute kidney injury

BACKGROUND AND AIMS

Acute kidney injury (AKI) commonly occurs in patients with decompensated cirrhosis. Urinary neutrophil gelatinase-associated lipocalin (uNGAL) could help discriminate between different etiologies of AKI. The aim of this study was to investigate the use of uNGAL in (1) the differential diagnosis of AKI, (2) predicting the response to terlipressin and albumin in patients with hepatorenal syndrome-AKI (HRS-AKI), and (3) predicting in-hospital mortality in patients with AKI.

APPROACH AND RESULTS

One hundred sixty-two consecutive patients with cirrhosis and AKI were included from 2015 to 2020 and followed until transplant, death, or 90 days. Standard urinary markers and uNGAL were measured. Data on treatment, type, and resolution of AKI were collected. Thirty-five patients (21.6%) had prerenal AKI, 64 (39.5%) HRS-AKI, 27 (16.7%) acute tubular necrosis-AKI (ATN-AKI), and 36 (22.2%) a mixed form of AKI. Mean values of uNGAL were significantly higher in ATN-AKI than in other types of AKI (1162 ng/ml [95% CI 423-2105 ng/ml] vs. 109 ng/ml [95% CI 52-192 ng/ml]; p  < 0.001). uNGAL showed a high discrimination ability in predicting ATN-AKI (area under the receiver operating characteristic curve, 0.854; 95% CI 0.767-0.941; p  < 0.001). The best-performing threshold was found to be 220 ng/ml (sensitivity, 89%; specificity, 78%). The same threshold was independently associated with a higher risk of nonresponse (adjusted OR [aOR], 6.17; 95% CI 1.41-27.03; p  = 0.016). In multivariable analysis (adjusted for age, Model for End-Stage Liver Disease, acute-on-chronic liver failure, leukocytes, and type of AKI), uNGAL was an independent predictor of in-hospital mortality (aOR, 1.74; 95% CI 1.26-2.38; p  = 0.001).

CONCLUSIONS

uNGAL is an adequate biomarker for making a differential diagnosis of AKI in cirrhosis and predicting the response to terlipressin and albumin in patients with HRS-AKI. In addition, it is an independent predictor of in-hospital mortality.

Clinical and pathophysiological understanding of the hepatorenal syndrome: Still wrong or still not exactly right?

The hepatorenal syndrome (HRS) is one major extrahepatic complication of end-stage liver diseases. While circulatory dysregulation is considered as primary etiology for HRS, cirrhosis-related (systemic) inflammation and/or cardial dysfunction may also play a key pathogenic role in HRS development. Exclusion of other causes of acute kidney injury (AKI) is required for diagnosis of HRS-AKI by the definition of the International Club of Ascites. However, the pathophysiology of HRS is not understood completely and there are still limited therapeutic options. Reversibility of renal dysfunction after liver transplantation indicates that HRS-AKI is a functional disorder caused by altered cellular function. The interplay between systemic inflammation and the onset of kidney-related hypometabolism may have a key role and needs to be studied in depth. This minireview challenges simplified views of the HRS in the context of diagnostics and therapy stressing the need for further evidence to advance the knowledge on this syndrome.

Definitions, phenotypes, and subphenotypes in acute kidney injury-Moving towards precision medicine

The current definition of acute kidney injury (AKI) is generic and, based only on markers of function, is unsuitable for guiding individualized treatment. AKI is a complex syndrome with multiple presentations and causes. Targeted AKI management will only be possible if different phenotypes and subphenotypes of AKI are recognised, based on causation and related pathophysiology. Molecular signatures to identify subphenotypes are being recognised, as specific biomarkers reveal activated pathways. Assessment of individual clinical risk needs wider dissemination to allow identification of patients at high risk of AKI. New and more timely markers for glomerular filtration rate (GFR) are available. However, AKI diagnosis and classification should not be limited to GFR, but include tubular function and damage. Combining damage and stress biomarkers with functional markers enhances risk prediction, and identifies a population enriched for clinical trials targeting AKI. We review novel developments and aim to encourage implementation of these new techniques into clinical practice as a strategy for individualizing AKI treatment akin to a precision medicine-based approach.