cirrhosis is characterized by circulatory changes corresponding to a hyperkinetic state with arterial vasodilatation , decreased systemic vascular resistance , and increased cardiac output .
hyperkinetic state and vasodilatation worsen in parallel with the deterioration in liver function . in patients with end - stage cirrhosis ,
arteriolar vasodilatation is no longer compensated by an increase in cardiac output , resulting in a state of arterial underfilling .
arterial underfilling , in turn , results in the activation of vasoconstrictor systems , which causes intense intrarenal vasoconstriction and a marked decrease in glomerular filtration rate ( gfr ) and eventually leads to hepatorenal syndrome ( hrs ) .
the increase in creatinine can be abrupt ( type i hrs ) or follow a more progressive course ( type ii hrs ) .
a first set of criteria had been proposed in the mid-'90s to better differentiate hrs from other causes of acute renal failure in cirrhosis , the absence of improvement with volume expansion being central in the definition of hrs . however , these criteria proved to be too restrictive .
for instance , ongoing bacterial infection was considered an exclusion criterion although experience shows that hrs frequently is triggered by infections .
the diagnostic criteria were revisited in 2007 in order to be less restrictive . however , these criteria still have some limitations .
firstly , it has been shown that a substantial proportion of patients who are undergoing transjugular renal biopsy and who have a clinical diagnosis of hrs do have intrinsic kidney changes , especially tubulointerstitial injury resulting from either comorbidities or chronic ischemia . secondly , the limit of a creatinine level of more than 1.5 mg / dl to define hrs may be inappropriate . indeed , owing to muscle wasting
, some cirrhotic patients with a serum creatinine level of below 1 mg / dl may already have a marked decrease in true gfr . in the previous issue of critical care , a group of experts , including not only hepatologists but also nephrologists and intensivists , reported the results of a workshop aimed at reviewing current knowledge in the field of hrs and proposing new classifications , based on the widely used rifle ( risk , injury , failure , loss , and end - stage kidney disease ) criteria , of all forms of renal impairment in cirrhosis .
the group proposed the term ' hepatorenal disorder ' to define any kind of kidney disease that is functional or structural in nature in patients with cirrhosis .
acute kidney injury is considered at an earlier stage in patients with a creatinine increase of at least 0.3 mg / dl within 48 hours and/or a 1.5 or more increase in creatinine from baseline .
this new classification may help initiate specific therapy at an earlier stage and increase the chance for recovery .
this classification is also more appropriate to identify any kind of kidney injury within a wide spectrum of causes of acute , chronic , and acute - on - chronic kidney diseases in cirrhosis .
however , even if the patients are identified at an earlier stage , the revised classification does not clearly differentiate those who may benefit from medical therapies of hrs ( that is , terlipressin or noradrenaline )   from those who may not .
in addition , this classification does not help address the important issue of reversibility after liver transplantation .
in most western countries , the model for end - stage liver disease ( meld ) score determines priority for allocation in liver transplantation .
since creatinine is one of the three components of the meld score ( along with bilirubin and international normalized ratio ) , the proportion of patients undergoing liver transplantation with renal insufficiency has significantly increased in the meld era .
the rate of post - transplant chronic renal failure has also increased with a 5-year cumulative incidence that may exceed 20% .
finally , the number of combined liver and kidney transplantations has also increased with declining outcomes , raising the issue of overuse and misuse in combined transplantation .
overall , circulatory changes in cirrhosis necessarily have a deleterious impact on the course of any chronic kidney disease , regardless of the cause and mechanisms .
a challenging issue is to determine more accurately the potential for improvement with liver transplantation alone , by reversing hyperkinetic state , in order to better identify those who need a combined liver and kidney transplantation and those who do not . in theory , hrs is a functional disorder that is fully reversible with liver transplantation .
however , as discussed above , a number of patients with hrs have intrinsic kidney changes that may not improve after transplantation .
therefore , another issue is to better identify the subgroup of hrs patients who are likely to rapidly develop end - stage renal failure after transplantation .
unfortunately , in patients who have end - stage cirrhosis complicated by hrs and who are not candidates for transplantation , therapies such as terlipressin or albumin dialysis provide only a modest survival benefit . in the majority
gfr : glomerular filtration rate ; hrs : hepatorenal syndrome ; meld : model for end - stage liver disease .
 hepatorenal syndrome ( hrs ) is a pre - renal azotemia - like acute renal failure occurring in patients with end - stage cirrhosis . 
 hrs results from arteriolar vasodilatation , arteriolar underfilling , and intense renal vasoconstriction . by definition , it is not responsive to volume expansion , and the prognosis is especially poor even with the use of terlipressin or albumin dialysis or both . it may be difficult , on the basis of the current criteria , to clearly differentiate hrs from other causes of acute renal failure in cirrhosis . 
 in addition , patients with hrs frequently have underlying chronic kidney changes that may not be reversible after transplantation . in the previous issue of critical care , 
 a group of experts proposed a new classification of acute , acute - on - chronic , or chronic renal impairment in cirrhosis on the basis of the rifle ( risk , injury , failure , loss , and end - stage kidney disease ) criteria . 
 the group proposed the term ' hepatorenal disorder ' to define patients with advanced cirrhosis and kidney dysfunction at an earlier stage , regardless of the mechanisms . 
 as stated by the authors , more data are needed to clearly identify , by non - invasive means , those with a potential for improvement with liver transplantation and those who can undergo a combined liver and kidney transplantation . 