Bile cast nephropathy: A case report and review of the literature

The role of serum magnesium in the prediction of acute kidney injury after total aortic arch replacement: A prospective observational study

Background

Considerable morbidity and death are associated with acute kidney damage (AKI) following total aortic arch replacement (TAAR). The relationship between AKI following TAAR and serum magnesium levels remains unknown. The intention of this research was to access the predictive value of serum magnesium levels on admission to the Cardiovascular Surgical Intensive Care Unit (CSICU) for AKI in patients receiving TAAR.

Methods

From May 2018 to January 2020, a prospective, observational study was performed in the Guangdong Provincial People's Hospital CSICU. Patients accepting TAAR admitted to the CSICU were studied. The Kidney Disease: Improving Global Outcomes (KDIGO) definition of serum creatinine was used to define AKI, and KDIGO stages two or three were used to characterize severe AKI. Multivariable logistic regression and area under the curve receiver-operator characteristic curve (AUC-ROC) analysis were conducted to assess the predictive capability of the serum magnesium for AKI detection. Finally, the prediction model for AKI was established and internally validated.

Results

Of the 396 enrolled patients, AKI occurred in 315 (79.5%) patients, including 154 (38.8%) patients with severe AKI. Serum magnesium levels were independently related to the postoperative AKI and severe AKI (both, P < 0.001), and AUC-ROCs for predicting AKI and severe AKI were 0.707 and 0.695, respectively. Across increasing quartiles of serum magnesium, the multivariable-adjusted odds ratios (95% confidence intervals) of postoperative AKI were 1.00 (reference), 1.04 (0.50-2.82), 1.20 (0.56-2.56), and 6.19 (2.02-23.91) (P for Trend < 0.001). When serum magnesium was included to a baseline model with established risk factors, AUC-ROC (0.833 vs 0.808, P = 0.050), reclassification (P < 0.001), and discrimination (P = 0.002) were further improved.

Conclusions

Serum magnesium levels on admission are an independent predictor of AKI. In TAAR patients, elevated serum magnesium levels were linked to an increased risk of AKI. In addition, the established risk factor model for AKI can be considerably improved by the addition of serum magnesium in TAAR patients hospitalized in the CSICU.

Acute hyperbilirubinemia determines an early subclinical renal damage: Evaluation of tubular biomarkers in cholemic nephropathy

BACKGROUND AND AIMS

Cholemic nephropathy is a cause of acute kidney injury occurring in patients with jaundice. The aim of this study was to evaluate early renal function impairment in patients with mild acute hyperbilirubinemia in the absence of alterations of the common parameters used in clinical practice (serum creatinine or urea) and with normal renal morphology. We studied urinary biomarkers of tubular damage urinary neutrophil gelatinase-associated lipocalin (u-NGAL), urinary beta-2-microglobulin (u-B2M), urinary osteopontin (u-OPN), urinary trefoil factor 3 (u-TFF3) and urinary Cystatin C (u-Cys).

METHODS

This is a case-control study investigating the following urinary biomarkers of tubular damage: u-NGAL, u-B2M, u-OPN, u-TFF3 and u-Cys, in patients with mild acute hyperbilirubinemia. Seventy-four patients were included in this study: 36 patients with jaundice and 38 patients without jaundice.

RESULTS

Subjects with jaundice (total bilirubin 12.4 ± 7.3 mg/dL) showed higher u-NGAL, u-B2M, u-OPN, u-TFF3 and u-Cys compared with controls. After logistic regression analyses, including the following independent variables: age, estimated Glomerular Filtration Rate (eGFR), haemoglobin, diabetes, hypertension and jaundice, we observed a higher risk of elevated u-NGAL values (OR = 3.8, 95% CI 1.07-13.5, p = .03) and u-B2M (OR = 9.4, 95% CI 2.3-38.9, p = .0018) in jaundiced subjects. Moreover, urinary biomarkers had a direct correlation with serum cholestasis indexes.

CONCLUSIONS

This study demonstrated increased urinary biomarkers of tubular damage (u-NGAL, u-B2M, u-OPN, u-TFF3, and u-Cys) in patients with mild hyperbilirubinemia in comparison with a control group. These findings suggest early renal tubular damage in the absence of alterations of the normal parameters used in clinical practice (eGFR, serum urea and renal morphology).

Hepatotoxicity of Antibiotics and Antifungals and Their Safe Use in Hepatic Impairment

Idiosyncratic drug-induced liver injury (DILI) is a rare and unpredictable form of hepatotoxicity. While its clinical course is usually benign, cases leading to liver transplantation or death can occur. Based on modern prospective registries, antimicrobials including antibiotics and antifungals are frequently implicated as common causes. Amoxicillin-clavulanate ranks as the most common cause for DILI in the Western World. Although the absolute risk of hepatotoxicity of these agents is low, as their usage is quite high, it is not uncommon for practitioners to encounter liver injury following the initiation of antibiotic or antifungal therapy. In this review article, mechanisms of hepatoxicity are presented. The adverse hepatic effects of well-established antibiotic and antifungal agents are described, including their frequency, severity, and pattern of injury and their HLA risks. We also review the drug labeling and prescription guidance from regulatory bodies, with a focus on individuals with hepatic impairment.

Cholemic Nephropathy: Role in Acute Kidney Injury in Cholestasis and Cirrhosis

The concept of structural kidney damage and renal dysfunction as a result of jaundice attracted attention in the medical community in the early and mid-20th century. The postulated doctrine of the time was that the excretion of elevated concentrations of bile results in bile-stained casts occupying collecting and distal convoluted tubules, degeneration of tubular epithelium, and decreased renal function. Compared to the hepatorenal syndrome, the poster child of hepatology and nephrology collaboration, the notion of structural kidney damage and renal dysfunction as a result of cholemia lost its traction and has almost disappeared from modern textbooks. Today, cholemic nephropathy is experiencing a renaissance, with multiple case reports and case series of jaundiced patients with kidney dysfunction and evidence of bile acid casts upon histologic examination. Published cases include acute hepatitis, chronic liver injury, cirrhosis, and obstructive etiologies. Diagnosis of cholemic nephropathy is based on histological examination, typically showing intraluminal bile casts predominantly located in the distal tubules. In common bile duct-ligated mice, the histomorphological and functional alterations of cholemic nephropathy mimic those seen in humans. Some argue against the concept of cholemic nephropathy and postulate that bile casts are a secondary phenomenon. What we need are carefully designed trials to establish diagnostic criteria and subsequently translate this knowledge into evidence-based therapies.

Utilizing kidneys from a donor with bile-cast nephropathy

Here we discuss the successful utilization of a pair of deceased donor kidneys with bile-cast nephropathy. The donor had a kidney donor profile index of 48% and an acute kidney injury requiring continuous renal replacement therapy. Peak donor bilirubin was 40.5 mg/dL, and renal wedge biopsies showed bile-cast nephropathy. Both recipients had delayed graft function lasting up to 4 weeks. The 4-month biopsies showed mild interstitial fibrosis, tubular atrophy, and a resolution of bile casts. These kidney allografts showed the reversible course of cholemic nephropathy and the potential for increasing the utilization of previously discarded kidneys.

Case Report: Efficacy of albumin dialysis for the reversal of bile cast nephropathy-induced acute kidney injury

Background

Bile cast nephropathy (BCN) is an underdiagnosed renal complication associated with severe hyperbilirubinemia and is seen in patients with liver failure who have cholestatic complications. BCN-induced acute kidney injury (AKI) can require hemodialysis (HD), and the molecular adsorbent recirculating system (MARS) is a potentially useful therapeutic option.

Case summary

A 57-year-old male presented with jaundice persisting for 1 month, with laboratory test results indicative of hyperbilirubinemia and AKI. Abdominal imaging and a biopsy confirmed biliary ductal dilation secondary to a pancreatic head mass. The patient had rapidly progressive renal failure and refractory hyperbilirubinemia, despite biliary decompression, and was started on HD. Subsequent therapy with albumin dialysis therapy using MARS was successful in reversing the AKI, the cessation of HD, and the restoration of native renal function.

Conclusion

In the setting of BCN-induced AKI, timely initiation of MARS can provide a useful therapeutic strategy to reverse renal dysfunction and facilitate intrinsic renal recovery.

Acute Kidney Injury in Patients Admitted to the Intensive Care Unit: A Case Report

Patients admitted to the intensive care unit are prone to various complications, one of which is acute kidney injury (AKI). The etiology of acute kidney injury can be multifactorial. Among the various causes, sepsis remains the most prevalent. Cholemic nephropathy (CN) is a rare cause of AKI. Patients with CN usually present with elevated total bilirubin levels of greater than 20 mg/dl. However, CN has been reported in patients with total bilirubin levels of less than 20 mg/dL. These patients were found to have chronic elevations of bilirubin due to chronic liver disease rather than an acute rise in bilirubin levels. In this case series, we present two cases of patients with chronic liver disease who were admitted to the intensive care unit and were found to have AKI with elevated total bilirubin levels over 15 mg/dl.

Bile Cast Nephropathy Due to Hepatitis A-induced Hyperbilirubinemia: A Case Report and Literature Review

Bile cast nephropathy (BCN) or cholemic nephrosis (CN) is a form of acute renal dysfunction that occurs in the setting of hepatic dysfunction and hyperbilirubinemia. We present a case of a 58-year-old woman with a four-day history of intractable nausea, vomiting, and yellowish discoloration of her skin and eyes. Laboratory workup was notable for elevated total bilirubin (mainly direct), liver enzymes, creatinine, and blood urea nitrogen (BUN). The ultrasonography (US) of the abdomen showed hepatic steatosis. The hepatitis panel was remarkable for hepatitis A IgM. She was initially treated with supportive therapy. However, her bilirubin levels reached over 20 mg/dl, creatine was >8 mg/dl, and her estimated glomerular filtration rate (eGFR) was <10. Kidney biopsy showed pigmented casts consistent with BCN. She was started on hemodialysis with significant improvement in her symptoms and liver enzymes. This case underscores the importance of a broad differential diagnosis in cases with hyperbilirubinemia and acute kidney injury. BCN requires renal biopsy for a definitive diagnosis, and these patients usually require hemodialysis.

Bile Cast Nephropathy: A Comprehensive Review

Bile cast nephropathy (BCN) or cholemic nephropathy (CN) is an acute renal dysfunction, including acute kidney injury (AKI) in the setting of liver injury. It is a common phenomenon in patients with liver disease and is associated with significant morbidity and mortality. CN is characterized by hemodynamic changes in the liver, kidney, systemic circulation, intratubular cast formation, and tubular epithelial cell injury. CN has been overlooked as a differential diagnosis in chronic liver disease patients due to more importance to hepatic injury. However, frequent and considerable reporting of case reports recently has further investigated this topic in the last two decades. This review determines the evidence behind the potential role of bile acids and bilirubin in acute renal dysfunction in liver injury, summarizing the implied pathophysiology risk factors, and incorporating the therapeutic mechanisms and outcomes.

Bile acid nephropathy induced by anabolic steroids: A case report and review of the literature

Bile acid nephropathy also known as cholemic nephropathy is a rare and overlooked form of acute kidney injury that occurs in the setting of severe hyperbilirubinemia. The exact etiology remains unknown, and there is a lack of treatment guidelines for this clinical condition. Anabolic steroids are known to cause hepatoxicity occasionally leading to acute kidney injury. We report the case of a 27-year-old male patient who developed bile acid nephropathy as a result of severe hyperbilirubinemia secondary to anabolic steroids-induced liver injury. He was conservatively managed. We review the current literature touching on the etiology, pathophysiology, diagnosis, and management of bile acid nephropathy in an attempt to shed light on this clinical condition, which may present as a diagnostic and therapeutic challenge.

Cholemic Nephropathy as Cause of Acute and Chronic Kidney Disease. Update on an Under-Diagnosed Disease

Cholemic nephropathy (CN) is a recognized cause of acute kidney injury (AKI) in patients with severe hyperbilirubinemia (sHyb) and jaundice. Pathophysiological mechanisms of CN are not completely understood, but it seems caused both by direct toxicity of cholephiles and bile casts formation in nephrons enhanced by prolonged exposure to sHyb, particularly in the presence of promoting factors, as highlighted by a literature reviewed and by personal experience. The aim of our update is to retrace CN in its pathophysiology, risk factors, diagnosis and treatment, underlining the role of sHyb, promoting factors, and CN-AKI diagnostic criteria in the different clinical settings associated with this often-concealed disease. Our purpose is to focus on clinical manifestation of CN, exploring the possible transition to CKD. Cholemic nephropathy is an overlooked clinical entity that enters differential diagnosis with other causes of AKI. Early diagnosis and treatment are essential because renal injury could be fully reversible as rapidly as bilirubin levels are reduced. In conclusion, our proposal is to introduce an alert for considering CN in diagnostic and prognostic scores that include bilirubin and/or creatinine with acute renal involvement, with the aim of early diagnosis and treatment of sHyb to reduce the burden on renal outcome.

Targeted LC-MS/MS Profiling of Bile Acids in Various Animal Tissues

Bile acids are being increasingly investigated in humans and laboratory animals as markers for various diseases in addition to their important functions, such as promoting the emulsification in fat digestion and preventing gallstone formation. In humans and animals, primary bile acids are formed from cholesterol in the liver, converted in the intestine into various secondary bile acids by the intestinal microbiota and reabsorbed in the terminal ileum, and partially returned to the liver. A universal high-throughput workflow, including a simple workup, was applied as a tool for bile acid analysis in animal studies. The complex bile acid profiles in various tissues, organs, and body fluids from different animals were mapped using a newly developed comprehensive liquid chromatography-tandem mass spectrometry method. The method can also be used in screening food to obtain information about the nutritional content of bile acids. This could be relevant to investigations on various animal diseases and on the bioavailability of bile acids that pass through the gastric tract.

Renal tubular injury in hyperbilirubinemia: Bile cast nephropathy

The toxic renal accumulation of bile pigment sparked clinical intrigue almost a century ago. More recently, however, the identification of bile casts within renal tubules in patients with liver dysfunction has been largely overlooked. We have reviewed the literature, including natural history, pathophysiology, and potential treatment of bile cast nephropathy (BCN). We report two cases of acute kidney injury (AKI) associated with acute-on-chronic liver failure in which prolonged hyperbilirubinemia and bile cast identification on renal biopsy evoked the diagnosis of BCN.

Bile Cast Nephropathy an Important Biliary Culprit of Kidney Injury

Bile cast nephropathy (BCN) is a rare form of acute kidney injury (AKI) that occurs in the setting of hyperbilirubinemia. We present the case of a 67 year-old male with severe kidney injury who was found to have obstructive cholestasis. By way of this report, we aim to expand upon the existing literature and showcase the importance of timely endoscopic retrograde cholangio-pancreatography (ERCP) in this setting, in order to prevent irreversible kidney damage.

Continuous renal replacement therapy and extended indications

Extracorporeal blood purification (EBP) techniques provide support for critically ill patients with single or multiple organ dysfunction. Continuous renal replacement therapy (CRRT) is the modality of choice for kidney support for those patients and orchestrates the interactions between the different artificial organ support systems. Intensive care teams should be familiar with the concept of sequential extracorporeal therapy and plan on how to incorporate new treatment modalities into their daily practices. Importantly, scientific evidence should guide the decision-making process at the bedside and provide robust arguments to justify the costs of implementing new EBP treatments. In this narrative review, we explore the extended indications for CRRT as an adjunctive treatment to provide support for the heart, lung, liver, and immune system. We detail practicalities on how to run the treatments and how to tackle the most frequent complications regarding each of the therapies, whether applied alone or integrated. The physicochemical processes and technologies involved at the molecular level encompassing the interactions between the molecules, membranes, and resins are spotlighted. A clinical case will illustrate the timing for the initiation, maintenance, and discontinuation of EBP techniques.

The pathogenesis of renal injury in obstructive jaundice: A review of underlying mechanisms, inducible agents and therapeutic strategies

Kidney injury is one of the main complications of obstructive jaundice (OJ) and its pathogenesis has not been clarified. As an independent risk factor for OJ associated with significant morbidity and mortality, it can be mainly divided into two types of morphological injury and functional injury. We called these dysfunctions caused by OJ-induced kidney injury as OJKI. However, the etiology of OJKI is still not fully clear, and research studies on how OJKI becomes a facilitated factor of OJ are limited. This article reviews the underlying pathological mechanism from five aspects, including metabolisms of bile acids, hemodynamic disturbances, oxidative stress, inflammation and the organic transporter system. Some nephrotoxic drugs and measures that can enhance or reduce the renal function with potential intervention in perioperative periods to alleviate the incidence of OJKI were also described. Furthermore, a more in-depth study on the pathogenesis of OJKI from multiple aspects for exploring more targeted treatment measures were further put forward, which may provide new methods for the prevention and treatment of clinical OJKI and improve the prognosis.

Rifampicin for Treatment of Cholestatic Pruritus Caused by Drug-Induced Acute Liver Injury as Assessed by the RUCAM Classification

A male bodybuilder of 39 years of age developed severe pruritus, nausea, and jaundice after injecting anabolic steroids purchased on the black market. The patient had no history of liver disease and no risk factors for viral hepatitis. Extensive laboratory testing, radiographic imaging, and liver biopsy excluded a majority of potential pathologies. The patient was diagnosed with drug-induced acute liver injury and secondary acute renal failure most likely caused by testosterone purchased on the black market. The pruritus caused insomnia and significant psychological distress. Treatment was initiated with cholestyramine and naltrexone for one week with no effect on the pruritus. Subsequently, all medications were stopped, and rifampicin was started. Pruritus resolved after starting rifampicin, and liver and kidney function improved rapidly and normalized within 5 months.

Acute Renal Failure Due to Bile Cast Nephropathy: An Overlooked Cause of Kidney Injury

Acute kidney injury in the setting of hyperbilirubinemia presents a diagnostic challenge. Hepatorenal syndrome takes precedence as a diagnosis in these cases. Bile cast nephropathy is a diagnosis that gets relatively low consideration. The most accurate diagnostic tool for bile cast nephropathy is a renal biopsy, which may present a challenge in certain clinical settings. There are no set guidelines for its management. While the exact cause of the condition is unknown, it is presumed to be secondary to multiple concurrent insults to the kidney including direct toxicity from bile acids, obstruction caused by bile casts, and systemic hypo-perfusion from vasodilation. It is believed that plasmapheresis and albumin dialysis have been associated with some recovery of renal function. We present a case of acute renal failure in a patient with obstructive jaundice, who responded to dialysis and biliary drain insertion.

Poly (ADP-Ribose) polymerase-1 (PARP-1) overactivity plays a pathogenic role in bile acids-induced nephrotoxicity in cholestatic rats

Cholestatic liver disease is a clinical complication with a wide range of etiologies. The liver is the primary organ influenced by cholestasis. Other organs, rather than the liver (e.g., kidneys), could also be affected by cholestatic liver disease. Cholestasis-induced renal injury is known as cholemic nephropathy (CN). Although the structural and functional alterations of the kidney in cholestasis have been well described, the cellular and molecular mechanisms of CN are not well understood. Some studies mentioned the role of oxidative stress and mitochondrial impairment in CN. Several cellular targets, including proteins, lipids, and DNA, could be affected by oxidative stress. Poly (ADP-Ribose) polymerase-1 (PARP-1) is an enzyme that its physiological activity plays a fundamental role in DNA repair. However, PARP-1 overexpression is associated with enhanced oxidative stress and cell death. The current study was designed to evaluate the role of PARP-1 activity in the pathogenesis of CN. Bile duct ligated (BDL) rats were treated with nicotinamide (NA) as a PARP-1 inhibitor. Kidney, urine, and plasma samples were collected at scheduled time intervals (3, 7, 14, and 28 days after BDL surgery). Serum and urine biomarkers of kidney injury, markers of oxidative stress and DNA damage, PARP-1 expression and activity in the kidney tissue, inflammatory response, renal fibrosis markers, and kidney histopathological alterations were assessed. Significant changes in the serum and urine biomarkers of kidney injury were evident in the BDL rats. Markers of oxidative stress were increased, and tissue ATP levels and antioxidant capacity were decreased in the kidney of cholestatic animals. A significant increase in PARP-1 expression and activity was evident in BDL rats (3, 7, 14, and 28 days after BDL). Moreover, inflammatory response (IL-1β and TNF-α expression; and myeloperoxidase activity), renal tissue histopathological alterations, and kidney fibrosis (α-SMA and TGF-β expression, as well as collagen deposition) were detected in cholestatic animals. It was found that the PARP-1 inhibitor, NA (50 and 100 mg/kg, i.p), significantly mitigated cholestasis-induced renal injury. The positive effects of NA were more significant at a lower dose and the early stage of CN. These data indicate a pathogenic role for PARP-1 overexpression in CN.

Liver Graft Failure and Bile Cast Nephropathy

The consequences of graft failure after liver transplantation (LT) range far beyond the liver. The kidneys are often affected, where persistent and progressive cholestasis can result in acute kidney injury (AKI) leading to the development of bile cast nephropathy (BCN). BCN is an often unrecognized condition that is characterized by proximal tubulopathy and the formation of bile casts in the distal tubules, which is almost diagnosed exclusively on a kidney biopsy or autopsy. This condition is potentially reversible, provided the bilirubin levels can be reduced early. LT may represent a treatment option in the case of irreversible liver (or liver graft) failure, which is beneficial for both the liver and the kidney. This paper reports a case of BCN in a patient with idiopathic graft failure after LT. Despite his chronic kidney disease, liver re-transplantation led to the successful improvement of his AKI.

Bile cast nephropathy: when the kidneys turn yellow

Kidney injury is a common finding in patients with liver disease. Bile cast nephropathy (also known as cholemic nephropathy) is an overlooked cause of renal injury in patients with hyperbilirubinemia. It can occur as a result of the toxic effects of bilirubin and bile acids on the renal tubules via several mechanisms. Bile cast nephropathy has characteristic histopathological changes consisting of bilirubin cast deposition in the distal nephron along with tubular epithelial cell injury. Treatment is based on the reversal of liver injury. This review aims to describe bile cast nephropathy in terms of its clinical and morphological features and to shed light on diagnostic techniques. In addition, we present data on management of such nephropathy while reviewing all the reported cases of bile cast nephropathy.

Role of inflammation and inflammasome activation in human bile cast nephropathy

Bile cast nephropathy (BCN) is an underdiagnosed cause of acute kidney injury (AKI). The precise pathogenesis of bilirubin tubular toxicity remains unknown. The aim of this study is to explore the cellular and molecular pathophysiology of human BCN. Paraffin-embedded sections of renal biopsy tissue from a BCN patient were stained by immunohistochemistry (IHC) for oxidative stress (4-hydroxynonenal), immune cell subpopulations, including dendritic cells (CD1c), macrophages (CD68) and T cells (CD3), and inflammasome activation by staining for active-caspase-1 and the inflammasome adaptor protein, ASC (apoptosis-associated speck-like protein containing a caspase activation and recruitment domain). Quantitative analyses of IHC staining were compared to healthy renal cortical tissue. We identified yellow to brown granular casts within the BCN case, consistent with the presence of bile pigment. The presence of bile pigment was associated with strong tubular 4-hydroxynonenal staining intensity, a marker of oxidative stress. Diffuse tubulointerstitial inflammatory cell infiltrate was detected, with elevated CD1c, CD68 and CD3 staining. Foci of inflammasome activity were co-localized with this intense immune cell infiltration, with increased active-caspase-1 and ASC staining. Our findings are the first to suggest that bile casts may lead to oxidative stress and trigger the inflammasome signalling cascade, leading to interstitial inflammation and driving AKI pathobiology. SUMMARY AT A GLANCE The report suggests that bile casts may lead to oxidative stress and trigger the inflammasome signalling cascade, leading to interstitial inflammation and driving bile cast nephropathy pathobiology.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), NCT02443389.

Murine epithelial sodium (Na+) channel regulation by biliary factors

The epithelial sodium channel (ENaC) mediates Na+ transport in several epithelia, including the aldosterone-sensitive distal nephron, distal colon, and biliary epithelium. Numerous factors regulate ENaC activity, including extracellular ligands, post-translational modifications, and membrane-resident lipids. However, ENaC regulation by bile acids and conjugated bilirubin, metabolites that are abundant in the biliary tree and intestinal tract and are sometimes elevated in the urine of individuals with advanced liver disease, remains poorly understood. Here, using a Xenopus oocyte-based system to express and functionally study ENaC, we found that, depending on the bile acid used, bile acids both activate and inhibit mouse ENaC. Whether bile acids were activating or inhibiting was contingent on the position and orientation of specific bile acid moieties. For example, a hydroxyl group at the 12-position and facing the hydrophilic side (12α-OH) was activating. Taurine-conjugated bile acids, which have reduced membrane permeability, affected ENaC activity more strongly than did their more membrane-permeant unconjugated counterparts, suggesting that bile acids regulate ENaC extracellularly. Bile acid-dependent activation was enhanced by amino acid substitutions in ENaC that depress open probability and was precluded by proteolytic cleavage that increases open probability, consistent with an effect of bile acids on ENaC open probability. Bile acids also regulated ENaC in a cortical collecting duct cell line, mirroring the results in Xenopus oocytes. We also show that bilirubin conjugates activate ENaC. These results indicate that ENaC responds to compounds abundant in bile and that their ability to regulate this channel depends on the presence of specific functional groups.

Severe cholestatic hyperbilirubinaemia secondary to thyrotoxicosis complicated with bile cast nephropathy treated with plasma exchange and haemodialysis

Thyrotoxicosis rarely presents as cholestatic hyperbilirubinaemia, and severe bilirubin elevation may lead to bile cast nephropathy. We present a case of a young woman with newly diagnosed Graves' disease with thyrotoxicosis who developed severe hyperbilirubinaemia and bile cast nephropathy. Serial plasma exchange and temporary haemodialysis led to full renal recovery. After treatment of her thyrotoxicosis with antithyroid medication and radioactive iodine ablation, her bilirubin normalised.

Cholemic Nephropathy Causes Acute Kidney Injury and Is Accompanied by Loss of Aquaporin 2 in Collecting Ducts

Impairment of renal function often occurs in patients with liver disease. Hepatorenal syndrome is a significant cause of acute kidney injury (AKI) in patients with cirrhosis (HRS-AKI, type 1). Causes of non-HRS-AKI include cholemic nephropathy (CN), a disease that is characterized by intratubular bile casts and tubular injury. As data on patients with CN are obtained primarily from case reports or autopsy studies, we aimed to investigate the frequency and clinical course of CN. We identified 149 patients who underwent kidney biopsy between 2000 and 2016 at the Department of Gastroenterology, Hepatology and Endocrinology at Hannover Medical School. Of these, 79 had a history of liver disease and deterioration of renal function. When applying recent European Association for the Study of the Liver criteria, 45 of 79 patients (57%) presented with AKI, whereas 34 patients (43%) had chronic kidney disease (CKD). Renal biopsy revealed the diagnosis of CN in 8 of 45 patients with AKI (17.8%), whereas none of the patients with CKD was diagnosed with CN. Univariate analysis identified serum bilirubin, alkaline phosphatase, and urinary bilirubin and urobilinogen as predictive factors for the diagnosis of CN. Histological analysis of AKI patients with normal bilirubin, elevated bilirubin, and the diagnosis of CN revealed loss of aquaporin 2 (AQP2) expression in collecting ducts in patients with elevated bilirubin and CN. Biopsy-related complications requiring medical intervention occurred in 4 of 79 patients (5.1%). Conclusion: CN is a common finding in patients with liver disease, AKI, and highly elevated bilirubin. Loss of AQP2 in AKI patients with elevated bilirubin and CN might be the result of toxic effects of cholestasis and in part be responsible for the impairment of renal function.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

Bile Cast Nephropathy: A Pathologic Finding with Manifold Causes Displayed in an Adult with Alcoholic Steatohepatitis and in a Child with Wilson's Disease

Bile cast nephropathy (BCN) is seen in patients who have acute kidney injury and severe hyperbilirubinemia due to a wide range of hepatobiliary system diseases. Findings seen by renal biopsy include acute tubular injury with necrotic and sloughed epithelial cells, yellow-green pigment within tubular epithelial cells, and pigmented granular casts. Hall's special stain for bile turns these casts green. In recent years, BCN has been described in a small number of case reports and clinical studies primarily in the setting of severe liver dysfunction. We present 2 diverse cases of BCN. The first involves an adult with hepatorenal syndrome secondary to alcoholic steatohepatitis and early cirrhosis. Second, we describe the first reported case of BCN in a child with fulminant hepatic failure due to Wilson's disease. Our cases expand the spectrum of causative diseases, and they provide further evidence that BCN is a distinct pathologic entity which may be found in both adult and pediatric patients with a variety of severe liver diseases.

Bile Cast Nephropathy: The Unknown Dangers of Online Shopping

Renal dysfunction in the setting of cholestatic liver disease is multifactorial but most often due to decreased kidney perfusion from intravascular volume depletion, acute tubular injury/necrosis, and hepatorenal syndrome. Drug-induced hepatotoxicity may be associated with a cholestatic injury pattern. We report a case of a 56-year-old man with a diagnosis of bile cast nephropathy, as a complication of drug-induced severe hyperbilirubinemia due to the abuse of intramuscular anabolic steroids bought on the internet to increase muscular mass for bodybuilding training. Kidney biopsy showed the histological pattern of diffuse potentially reversible tubular damage with intratubular bile casts obstructing the renal tubules. The patient developed acute kidney injury and needed dialysis treatment for 4 weeks until renal function recovered. The severity of the kidney injury and the requirement of hemodialysis observed in our patient are unique and have not been previously described. As full recovery of renal function is suspected with decreasing bilirubin levels, early recognition and treatment of the underlying disease is essential.

Bile cast nephropathy in a patient with cholangiocarcinoma - a case report

Bile cast nephropathy is characterized by the presence of bile casts associated with renal failure and/or proximal tubulopathy in cases of severe hyperbilirubinemia. The clinician should carefully examine the urine samples for characteristic bile‐stained granular casts in suspected case.

Cholemic or Bile Cast Nephropathy in a Child with Liver Failure

Cholemic or bile cast nephropathy is an under-reported entity characterized by acute renal dysfunction in patients with hepatic insult. Limited literature is available regarding its clinical presentation, pathogenesis and prognosis. We hereby present a pediatric case who presented with acute on chronic liver failure with renal dysfunction secondary to cholemic nephropathy.

Cholemic nephropathy - Historical notes and novel perspectives

Acute kidney injury is common in patients with liver disease and associated with significant morbidity and mortality. Besides bacterial infections, fluid loss, and use of nephrotoxic drugs AKI in liver disease may be triggered by tubular toxicity of cholephiles. Cholemic nephropathy, also known as bile cast nephropathy, supposedly represents a widely underestimated but important cause of renal dysfunction in cholestasic or advanced liver diseases with jaundice. Cholemic nephropathy describes impaired renal function along with characteristic histomorphological changes consisting of intratubular cast formation and tubular epithelial cell injury directed towards distal nephron segments. The underlying pathophysiologic mechanisms are not entirely understood and clear defined diagnostic criteria are still missing. This review aims to summarize (i) the present knowledge on clinical and morphological characteristics of cholemic nephropathy, (ii) available preclinical models, (iii) potential pathomechanisms especially the potential role of bile acids, and (iv) future diagnostic and therapeutic strategies for cholemic nephropathy. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

All That Glitters Yellow Is Not Gold: Presentation and Pathophysiology of Bile Cast Nephropathy

Background. Acute kidney injury (AKI) often manifests in patients with liver disease because of a prerenal cause and presents as acute tubular necrosis or hepatorenal syndrome. Distinguishing between these entities is important for prognosis and treatment. Some patients may develop AKI related to their underlying liver disease: for example, membranoproliferative glomerulonephritis or IgA nephropathy. Bile cast nephropathy is an often ignored differential diagnosis of AKI in the setting of obstructive jaundice. It is characterized by the presence of bile casts in renal tubules, which can possibly cause tubular injury through obstructive and direct toxic effects. Thus, AKI in patients with liver disease may have a structural component in addition to a functional one. Methods. In this study, we describe 2 patients with severe hyperbilirubinemia who developed AKI and underwent a kidney biopsy that revealed bile casts in tubular lumens, consistent with bile cast nephropathy. Results. One patient was treated aggressively for alcoholic hepatitis and required hemodialysis for AKI. The second patient was treated conservatively for drug-induced liver injury and did not require dialysis. Both patients saw a reduction in their bilirubin and creatinine toward baseline. Conclusion. Bile cast nephropathy is an important pathological entity that may account for the renal dysfunction in some patients with liver disease. It requires kidney biopsy for diagnosis and may often be overlooked given the scarcity of kidney biopsy in this particular clinical setting. The etiology is multifactorial, and it is often difficult to predict without the aid of a renal biopsy.