Pathophysiology of Hepatorenal Syndrome

Hepatorenal syndrome type 1 (HRS-1) is a unique form of acute kidney injury that affects individuals with decompensated cirrhosis with ascites. The primary mechanism leading to reduction of kidney function in HRS-1 is hemodynamic in nature. Cumulative evidence points to a cascade of events that led to a profound reduction in kidney perfusion. A state of increased intrahepatic vascular resistance characteristic of advanced cirrhosis and portal hypertension is accompanied by maladaptive peripheral arterial vasodilation and reduction in systemic vascular resistance and mean arterial pressure. As a result of a fall in effective arterial blood volume, there is a compensatory activation of the sympathetic nervous system and the renin-angiotensin system, local renal vasoconstriction, loss of renal autoregulation, decrease in renal blood flow, and ultimately a fall in glomerular filtration rate. Systemic release of nitric oxide stimulated by the fibrotic liver, bacterial translocation, and inflammation constitute key components of the pathogenesis. While angiotensin II and noradrenaline remain the critical mediators of renal arterial and arteriolar vasoconstriction, other novel molecules have been recently implicated. Although the above-described mechanistic pathway remains the backbone of the pathogenesis of HRS-1, other noxious elements may be present in advanced cirrhosis and likely contribute to the renal impairment. Direct liver-kidney crosstalk via the hepatorenal sympathetic reflex can further reduce renal blood flow independently of the systemic derangements. Tense ascites may lead to intraabdominal hypertension and abdominal compartment syndrome. Cardio-hemodynamic processes have also been increasingly recognized. Porto-pulmonary hypertension, cirrhotic cardiomyopathy, and abdominal compartment syndrome may lead to renal congestion and complicate the course of HRS-1. In addition, a degree of ischemic or toxic (cholemic) tubular injury may overlap with the underlying circulatory dysfunction and further exacerbate the course of acute kidney injury. Improving our understanding of the pathogenesis of HRS-1 may lead to improvements in therapeutic options for this seriously ill population.

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.

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.

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.

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.

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 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.