Acute kidney injury in acute-on-chronic liver failure: where does hepatorenal syndrome fit?

Renal dysfunction occurs in 25% to 50% of patients with cirrhosis admitted to the hospital with an acute episode of hepatic decompensation and may be due to underlying chronic kidney disease, an acute deterioration, or both. An acute deterioration in renal function in cirrhotic patients is now collectively referred to as acute kidney injury (AKI), which has been subclassified into different grades of severity that identify prognostic groups. Acute-on-chronic liver failure is characterized by acute hepatic and/or extrahepatic organ failure driven by a dysregulated immune response and systemic inflammatory response. AKI is also one of the defining features of ACLF and a major component in grading the severity of acute-on-chronic liver failure. As such, the pattern of AKI now observed in patients admitted to the hospital with acutely decompensated liver disease is likely to be one of inflammatory kidney injury including acute tubular injury (referred in this review as non-hepatorenal syndrome [HRS]-AKI) rather than HRS. As the management and supportive treatment of non-HRS-AKI potentially differ from those of HRS, then from the nephrology perspective, it is important to distinguish between non-HRS-AKI and HRS-AKI when reviewing patients with acute-on-chronic liver failure and AKI, so that appropriate and early management can be instituted.