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GENERAL CONSIDERATIONS

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Renal dysfunction is a common and serious problem in patients with advanced liver cirrhosis, estimated to occur in 20% of hospitalized patients with cirrhosis, and even more commonly at 54% in the outpatient setting. Renal dysfunction in cirrhosis has always been regarded as being related to the hemodynamic changes of systemic arterial vasodilatation and paradoxical renal vasoconstriction peculiar to cirrhosis without any structural changes in the kidneys. Such cases of renal dysfunction are known as functional renal failure and the prototype is hepatorenal syndrome (HRS). However, it is now recognized that many liver conditions such as alcoholic cirrhosis or hepatitis C can cause structural renal diseases, and yet the same patients can also develop hemodynamic abnormalities as cirrhosis advances, predisposing them to functional renal failure. Therefore, the demarcation between functional and structural renal diseases is no longer as clear as once thought. Furthermore, many common systemic conditions such as diabetes can cause both cirrhosis and nephropathy, once again blurring the separation between structural and functional renal diseases. Therefore, the concept of renal dysfunction in cirrhosis has been evolving, and that also includes redefining HRS, especially in light of recent changes in the definition of acute kidney injury (AKI) by the nephrology community.

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THE CONCEPT OF ACUTE KIDNEY INJURY

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The term AKI was adopted in the early 2000s to describe cases of acute kidney dysfunction that were trivial and therefore could not be termed renal failure, and yet they could lead to permanent structural damage in those patients who survived the insult. For example, it was observed in patients who underwent cardiac surgery that a rise in serum creatinine by 0.3 mg/dL (26.4 μmol/L) was associated with a negative effect on patient survival. There followed a flurry of academic activities reassessing the need for redefining renal dysfunction. Various definitions and diagnostic criteria of AKI, starting with the RIFLE criteria, then the Acute Kidney Injury Network (AKIN) criteria, then the Kidney Disease Improving Global Outcome (KDIGO) criteria appeared in the literature, with each set of criteria improving over the previous one. In order to conform to the changing concept of renal dysfunction in other patient populations, the hepatology community also felt that there was a need to redefine renal dysfunction in cirrhosis. The International Ascites Club, together with the Acute Dialysis Quality Initiative group, first proposed to define AKI in cirrhosis in 2011 as an increase in serum creatinine by 0.3 mg/dL (26.4 μmol/L) in less than 48 hours, or a 50% increase in serum creatinine from baseline, defined as a stable serum creatinine within the previous 6 months (Table 10–1), irrespective of the final serum creatinine level. This would allow the diagnosis of AKI at an earlier stage of renal dysfunction, thereby allowing earlier therapeutic intervention. The concept of chronic kidney disease (CKD) was also introduced, and acute on chronic kidney disease defined (Table 10–1). The International Ascites Club further clarified ...

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