Cystatin C: best biomarker for acute kidney injury and estimation of glomerular filtration rate in childhood cirrhosis

Novel acute kidney injury biomarkers and their utility in children and adolescents-overview

Acute kidney injury (AKI) affects a significant percentage of the pediatric population. Currently, the diagnosis of AKI in children still uses traditional laboratory methods (ex. creatinine or urea serum concentration and measurement of urine output). It has significant limitations. Early stages of AKI in children may be almost asymptomatic. In-depth assessment with the pRIFLE scale is helpful, but requires bladder catheterization and precise monitoring of hourly diuresis, as well as multiple blood draws to determine changes in creatinine concentration and estimate glomerular filtration rate (eGFR). The diagnostic methods lack a marker that would the early and potentially reversible phase of kidney damage. This paper reviews recent data on selected AKI markers in children, including their diagnostic and prognostic potential.

Variability in Meropenem Distribution and Clearance in Children with Sepsis: Population-Based Pharmacokinetics with Assessment of Renal Biomarkers

BACKGROUND AND OBJECTIVE

Meropenem dosing to achieve therapeutic exposure in critically ill children with sepsis is challenging due to a spectrum of renal function, from augmented renal clearance (ARC) to acute kidney injury (AKI). The objective of this study was to define meropenem plasma concentrations and pharmacodynamic exposure metrics in children with septic shock during the first 3 days of PICU hospitalization.

METHODS

We prospectively evaluated meropenem clearance (CLMERO) and volume of distribution (V1-MERO), innovatively assessing renal biomarkers (serum creatinine [SCr], serum cystatin C [SCys], and neutrophil gelatinase-associated lipocalin [SNgal]), in infants aged ≥ 4 weeks and children on intravenous (IV) meropenem 20 mg/kg every 8 h from 2019 to 2023. Cases with sepsis were matched to controls without sepsis.

RESULTS

Analysis included 27 participants (19 cases and 8 controls) with 309 meropenem serum concentrations. Median age was 11.8 (range 0.6-19.6) years, weight 36.3 (7.2-98.0) kg, SCr 0.33 (0.09-2.57) mg/dL, SCys 451.1 (178.3-1824.1) ng/mL, and SNgal 180.7 (23.2-1403.0) ng/mL. A 2-compartment, population pharmacokinetic (PK) model via NONMEM best described data, with weight on VMERO and allometric scaling on CLMERO. Using the final model with SCys in V1-MERO and estimated glomerular filtration rate (eGFR)-MS in CLMERO, the median V1-MERO was 0.23 (range 0.07-0.57) L/kg and CLMERO 0.15 (0.05-0.49) L/h/kg, with eGFR-MS 139 (23-365) mL/min/1.73 m2 from AKI to ARC. Meropenem clearance, V1-MERO and eGFR-MS were significantly decreased in cases versus controls, with higher variability of eGFR-MS in cases.

CONCLUSION

Wide variation in meropenem concentrations in children with sepsis as compared to those without sepsis prompt close monitoring of GFR and drug concentrations in this population.

Can Novel Biomarkers Effectively Predict Acute Kidney Injury in Liver or Kidney Transplant Recipients?

Acute kidney injury (AKI) constitutes a common complication associated with liver or kidney transplantation, which may significantly impact the graft condition and perioperative mortality. Current AKI diagnostic criteria based on serum creatinine (sCr) and urine output alterations are widely utilized in routine clinical practice. However, the diagnostic value of sCr may be limited by various confounding factors, including age, sex, reduced or increased muscle mass, and pre-existing chronic kidney disease (CKD). Furthermore, sCr is rather a late indicator of AKI, as its concentration tends to increase only when the severity of the injury is enough to decrease the estimated glomerular filtration rate (eGFR). Recent expertise highlights the need for novel biomarkers in post-transplantation AKI diagnosis, prediction of event-associated mortality, or evaluation of indications for renal replacement treatment (RRT). Over the last decade, the diagnostic performance of various AKI biomarkers has been assessed, among which some showed the potential to outperform sCr in AKI diagnosis. Identifying susceptible individuals, early diagnosis, and prompt intervention are crucial for successful transplantation, undisturbed graft function in long-term follow-up, and decreased mortality. However, the research on AKI biomarkers in transplantation still needs to be explored. The field lacks consistent results, rigorous study designs, and external validation. Considering the rapidly growing prevalence of CKD and cirrhosis that are associated with the transplantation at their end-stage, as well as the existing knowledge gap, the aim of this article was to provide the most up-to-date review of the studies on novel biomarkers in the diagnosis of post-transplantation AKI.

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.

Pediatric Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is characterized by an acute hepatic insult happening in a patient with underlying cirrhosis with compromised hepatic reserve leading to development of systemic inflammation, sepsis, and organ failure resulting in poor outcome in majority. While Asia Pacific Association for Study of Liver Diseases (APASL) emphasizes on early diagnosis before development of organ failure, European Association for Study of Liver Diseases (EASL) mandates the presence of organ failures to define ACLF. There is a lack of consensus definition of pediatric ACLF although recent APASL guidelines have tried to address the issue. While Wilson disease (WD) and autoimmune hepatitis (AIH) are the most common cause of underlying cirrhosis in children, acute viral hepatitis and flares of WD and AIH are the commonest acute precipitating events. Poor outcomes [death and liver transplantation (LT)] ranging from 19 to 59% have been reported. Prognosis in pediatric ACLF is usually better than that in adults due to greater proportion of treatable etiologies, lesser organ failures, comorbidities and better hepatic reserves. APASL ACLF Research Consortium (AARC) score more than or equal to 11 is predictive of poor 28-90 d mortality. Treatment of pediatric ACLF relies mainly on prompt diagnosis and medical management of a potentially treatable etiology of underlying cirrhosis. Bridging therapies, especially high volume plasma exchange can be initiated early as a bridge to LT or native liver recovery. Those with no improvement in 4-7 d should undergo LT before development of sepsis or multi-organ failure.

Midodrine reduces new-onset acute kidney injury and hyponatremia in children with cirrhosis and ascites awaiting liver transplantation: Results from an open-label RCT

OBJECTIVES

Midodrine, an oral α-1-adrenergic receptor agonist, counters arterial hypovolemia and reduces complications in adult patients with cirrhosis. This randomized controlled trial (RCT) aimed to assess the efficacy and safety of midodrine in preventing complications and improving survival in children with cirrhosis and ascites who are awaiting liver transplantation (LT).

METHODS

This open-label RCT conducted from January 2022 to May 2023 included children under 18 years with cirrhosis and ascites. Patients were randomized to receive either midodrine plus standard medical therapies (SMTs) or SMT alone. The primary outcome measure was the incidence of cirrhosis-related complications within 6 months.

RESULTS

Thirty-five subjects were enrolled and randomized. Patients in the midodrine arm had a lower incidence of new-onset acute kidney injury (AKI) compared with the SMT arm (11.1% vs. 41.2%). Patients in the midodrine arm showed a decline in serum creatinine and improvement in glomerular filtration rate, whereas no changes were observed in the SMT arm. There was a lower incidence of new-onset hyponatremia in the midodrine arm (20% vs. 56%). Midodrine led to reduction in plasma rennin activity (PRA) and improvement in systemic hemodynamics. There was no difference in the rate of resolution of ascites, recurrence of ascites, requirement of therapeutic paracentesis, cumulative albumin infusion requirement, episodes of spontaneous bacterial peritonitis, and hepatic encephalopathy between the two arms.

CONCLUSION

Midodrine, when added to SMT, was effective in reducing the incidence of new-onset AKI and hyponatremia in pediatric cirrhotics awaiting LT. It also improved systemic hemodynamics and showed a trend towards reducing PRA.

Predictive model of acute kidney injury after spontaneous intracerebral hemorrhage: A multicenter retrospective study

BACKGROUND AND OBJECTIVES

Acute kidney injury is a common comorbidity in patients with intracerebral hemorrhage. Although there are predictive models to determine risk of AKI in patients in critical care or post-surgical scenarios or in general medical floors, there are no models that specifically determine the risk of AKI in patients with ICH.

METHODS

Clinical features and laboratory tests were selected by previous studies and LASSO (least absolute shrinkage and selection operator) regression. We used multivariable logistic regression with a bidirectional stepwise method to construct ICH-AKIM (intracerebral hemorrhage-associated acute kidney injury model). The accuracy of ICH-AKIM was measured by the area under the receiver operating characteristic curve. The outcome was AKI development during hospitalization, defined as KDIGO (Kidney Disease: Improving Global Outcomes) Guidelines.

RESULTS

From four independent medical centers, a total of 9649 patients with ICH were available. Overall, five clinical features (sex, systolic blood pressure, diabetes, Glasgow coma scale, mannitol infusion) and four laboratory tests at admission (serum creatinine, albumin, uric acid, neutrophils-to-lymphocyte ratio) were predictive factors and were included in the ICH-AKIM construction. The AUC of ICH-AKIM in the derivation, internal validation, and three external validation cohorts were 0.815, 0.816, 0.776, 0.780, and 0.821, respectively. Compared to the univariate forecast and pre-existing AKI models, ICH-AKIM led to significant improvements in discrimination and reclassification for predicting the incidence of AKI in all cohorts. An online interface of ICH-AKIM is freely available for use.

CONCLUSION

ICH-AKIM exhibited good discriminative capabilities for the prediction of AKI after ICH and outperforms existing predictive models.

Effects and Mechanisms of Peritoneal Resuscitation on Acute Kidney Injury After Severe Burns in Rats

INTRODUCTION

Acute kidney injury (AKI) is a common complication in severe burn patients with poor prognosis and high mortality. Reduced kidney perfusion induced by the decreased effective circulating blood volume after severe burn is a common cause of AKI. Routine intravenous resuscitation (IR) is difficult or delayed in extreme conditions such as war and disaster sites. Peritoneal resuscitation (PR) is a simple, rapid resuscitation strategy via a puncture in the abdominal wall. This study investigated whether PR is a validated resuscitation strategy for AKI after severe burns in rats and explored its mechanisms.

MATERIALS AND METHODS

Eighty Sprague-Dawley rats were randomized into four groups: (1) sham group; (2) IR group, which was characterized by the full thickness burn of 50% of the total body surface area received IR immediately post-injury; (3) early PR group, in which rats with the same burn model received PR immediately post-injury; and (4) delayed resuscitation (DR) group, in which rats with the same burn model received no resuscitation within 3-hour post-injury. PR and DR groups animals received IR after 3-hour post-injury. The survival rate, mean arterial pressure, renal histopathology, renal function, indicators of renal injury, and renal hypoxia-inducible factor-1α and NADPH oxidase 4 (NOX4) proteins of rats were measured at 3 h, 12 h, and 24 h post-injury.

RESULTS

Compared with rats in the DR group, rats in the PR group had a significantly improved survival rate (100% vs. 58.3% at 24 h, P = 0.0087), an increased mean arterial pressure (92.6 ± 6.6 vs. 65.3 ± 10.7, 85.1 ± 5.7 vs. 61.1 ± 6.9, 90.1 ± 8.7 vs. 74.9 ± 7.4 mmHg, at 3 h, 12 h, and 24 h, P < 0.01), a reduced renal water content rate (51.6% ± 5.0% vs. 70.1% ± 6.8%, 57.6% ± 7.7% vs. 69.5% ± 8.7%, at 12 h and 24 h, P < 0.01), attenuated histopathological damage, reduced serum creatinine expression (36.36 ± 4.27 vs. 49.98 ± 2.42, 52.29 ± 4.31 vs. 71.32 ± 5.2, 45.25 ± 2.55 vs. 81.15 ± 6.44 μmol/L, at 3 h, 12 h, and 24 h, P < 0.01) and BUN expression (7.62 ± 0.30 vs. 10.80 ± 0.58, 8.61 ± 0.32 vs. 28.58 ± 1.99, 8.09 ± 0.99 vs. 20.95 ± 1.02 mmol/L, at 3 h, 12 h, and 24 h, P < 0.01), increased kidney injury markers neutrophil gelatinase-associated lipocalin expression (95.09 ± 7.02 vs. 101.75 ± 6.23, 146.77 ± 11.54 vs. 190.03 ± 9.87, 112.79 ± 15.8 vs. 194.43 ± 11.47 ng/mL, at 3 h, 12 h, and 24 h, P < 0.01) and cystatin C expression (0.185 ± 0.006 vs. 0.197 ± 0.006, 0.345 ± 0.036 vs. 0.382 ± 0.013, 0.297 ± 0.012 vs. 0.371 ± 0.028 ng/mL, at 3 h, 12 h, and 24 h, P < 0.01), and reduced renal hypoxia-inducible factor-1α and NADPH oxidase 4 protein expression (P < 0.01). There was no significant difference between rats in the PR group and the IR group in the above indicators.

CONCLUSIONS

Early PR could protect severe burn injury rats from AKI. It may be an alternative resuscitation strategy in severe burn injury when IR cannot be achieved.

Imprecision remains to be improved in the measurement of serum cystatin C with heterogeneous systems

OBJECTIVES

Except for the large bias of some measurement systems for serum cystatin C (CysC) measurements, unacceptable imprecision has been observed for the heterogenous system. This study analyzed the external quality assessment (EQA) results in 2018-2021 to provide an insight into the imprecision of CysC assays.

METHODS

Five EQA samples were sent to participating laboratories every year. Participants were divided into reagent/calibrator-based peer groups, for which the robust mean of each sample and robust coefficient of variation (CV) were calculated by Algorithm A from ISO 13528. Peers with more than 12 participants per year were selected for further analysis. The limit of CV was determined to be 4.85% based on clinical application requirements. The concentration-related effect on CVs was investigated using logarithmic curve fitting; the difference in medians and robust CVs between instrument-based subgroups was also evaluated.

RESULTS

The total number of participating laboratories increased from 845 to 1,695 in four years and heterogeneous systems remained the mainstream (≥85%). Of 18 peers with ≥12 participants, those using homogeneous systems showed relatively steady and small CVs over four years, with the mean four-year CVs ranging from 3.21 to 3.68%. Some peers using heterogenous systems showed reduced CVs over four years, while 7/15 still had unacceptable CVs in 2021 (5.01-8.34%). Six peers showed larger CVs at the low or high concentrations, and some instrument-based subgroups presented greater imprecision than others.

CONCLUSIONS

More efforts should be made to improve the imprecision of heterogeneous systems for CysC measurement.

Norepinephrine May Exacerbate Septic Acute Kidney Injury: A Narrative Review

Sepsis, the most serious complication of infection, occurs when a cascade of potentially life-threatening inflammatory responses is triggered. Potentially life-threatening septic shock is a complication of sepsis that occurs when hemodynamic instability occurs. Septic shock may cause organ failure, most commonly involving the kidneys. The pathophysiology and hemodynamic mechanisms of acute kidney injury in the case of sepsis or septic shock remain to be elucidated, but previous studies have suggested multiple possible mechanisms or the interplay of multiple mechanisms. Norepinephrine is used as the first-line vasopressor in the management of septic shock. Studies have reported different hemodynamic effects of norepinephrine on renal circulation, with some suggesting that it could possibly exacerbate acute kidney injury caused by septic shock. This narrative review briefly covers the updates on sepsis and septic shock regarding definitions, statistics, diagnosis, and management, with an explanation of the putative pathophysiological mechanisms and hemodynamic changes, as well as updated evidence. Sepsis-associated acute kidney injury remains a major burden on the healthcare system. This review aims to improve the real-world clinical understanding of the possible adverse outcomes of norepinephrine use in sepsis-associated acute kidney injury.

Novel biomarkers of acute kidney injury in chronic liver disease: Where do we stand after a decade of research?

Acute kidney injury (AKI) is a frequently encountered complication in decompensated chronic liver disease (CLD) with an estimated prevalence of 20%-50% among hospitalized patients. AKI often heralds the onset of a downhill course in the natural history of CLD. Serum creatinine has several limitations as a stand-alone marker of AKI in patients with decompensated CLD. The concept of hepatorenal syndrome, the prototype of AKI in decompensated CLD, has evolved tremendously over recent years. There is emerging evidence of an additional "structural" component in the pathophysiology of hepatorenal syndrome-AKI, which was previously identified as a purely "functional" form of renal impairment. Lacunae in the existent biochemical arsenal for diagnosis and prognosis of AKI have fueled enthusiastic research in the field of novel biomarkers of kidney injury in patients with cirrhosis. The advent of these biomarkers provides a crucial window of opportunity to improve the diagnosis and clinical outcomes of this vulnerable cohort of patients. This review summarizes the dynamic concept of renal dysfunction in CLD and the available literature on the role of novel biomarkers of AKI in assessing renal function, identifying AKI subtypes, and predicting prognosis. There is special emphasis on the renal tubular injury marker, neutrophil gelatinase-associated lipocalin, the most exhaustively studied biomarker of AKI in the CLD population.

The UA Doppler Index, Plasma HCY, and Cys C in Pregnancies Complicated by Congenital Heart Disease of the Fetus

Background: Congenital heart disease/defect (CHD) is one of the most common congenital disabilities. Early diagnosis of CHD can improve the prognosis of newborns with CHD. The aim of this study was to evaluate the relationship between the factors and the onset of fetal congenital heart disease by measuring fetal umbilical artery (UA) Doppler index, maternal HCY, and Cys C levels during pregnancy. Methods: This retrospective study analyzed 202 fetuses with CHD, including 77 cases (39.1%) of simple CHD and 120 cases (60.9%) of complex CHD. Singleton pregnant women who were examined at the same time and whose malformation screening did not suggest any structural abnormalities in the fetus were assigned to the control group (n = 400). The UA Doppler index, plasma HCY, and Cys C levels were compared among the pregnant women across the three groups, and logistic regression analysis was performed on statistically significant markers. The ROC of UA S/D, PI, RI, HCY, and Cys C were plotted, and the area under the ROC (AUC) was calculated. Results: The UA S/D, PI, and RI in the complex CHD group were significantly higher than those in the control group (p < 0.05). The levels of HCY and Cys C in the CHD group were significantly higher than those in the control group (p < 0.05). HCY and S/D revealed a positive correlation (r = 0.157), and the difference was statistically significant (p < 0.001). Cys C and S/D were positively correlated (r = 0.131), and the difference was statistically significant (p < 0.05). The levels of UA Doppler indices, maternal plasma HCY, and Cys C were elevated in fetuses with CHD. The AUC of the combined test of the UA index, HCY, and Cys C was higher than that of each individual test. Conclusions: Elevated levels of the UA doppler indices, HCY, and Cys C during pregnancy are positively associated with the development of congenital heart disease in offspring. The combination of HCY and Cys C was the most efficient test for the diagnosis of CHD. We are the first to report that plasma Cys C levels of women pregnant with fetuses with CHD were higher than those of women pregnant with normal fetuses.

The Perspectives of Biomarkers in Predicting the Survival of the Renal Graft

Kidney transplantation (KT) is currently the elective approach for patients with end-stage renal disease. Although it is a safe choice for these patients, the early complications can lead to graft dysfunction. One of the most redoubtable complications is delayed graft function (DGF), having no specific treatment. The effects of DGF on the graft survival are large enough to justify the formulation of specific biological protocols. Therefore, discovering biomarkers of acute impairment in renal transplanted patients is required. Creatinine is a poor marker to establish the kidney injury. Estimated glomerular filtration rate together with creatinine is ready to approximately measure the kidney function. Different serum and urine proteins are being studied as possible predictive biomarkers for delayed graft function. This review will concentrate on recent and existing research which provide insight concerning the contribution of some molecules for the estimation and evaluation of graft function after kidney transplantation. Further studies examining various aspects of DGF after KT are urgently needed to address a hitherto less-known clinical question.

Urinary neutrophil gelatinase-associated lipocalin: Acute kidney injury in liver cirrhosis

Acute kidney injury (AKI) in liver cirrhosis is associated with poor clinical outcomes including an increased long and short-term mortality. The common type of AKI observed in patients with cirrhosis are prerenal AKI (PRA), hepatorenal syndrome (HRS) and acute tubular necrosis (ATN). Despite the growing knowledge and uniform definition for the diagnosis of AKI, there are several challenges including, early diagnosis and management. Precisely differentiating the type of AKI is critical, as therapies differ significantly. In this review, we summarize AKI in liver cirrhosis, their definition, pathophysiology and deficiencies of using the existing biomarker, serum creatinine. We outline the current clinical evidence on the novel biomarker urinary neutrophil gelatinase-associated lipocalin (uNGAL) and its potential role as a biomarker in the early detection, differentiation and prognostication of AKI. This review also briefly talks about other forthcoming biomarkers which hold promise in the management of AKI in liver cirrhosis.