New Developments in Hepatorenal Syndrome

Abstract

Hepatorenal syndrome (HRS) continues to be one of the major complications of decompensated cirrhosis, leading to death in the absence of liver transplantation. Challenges in precisely evaluating renal function in the patient with cirrhosis remain because of the limitations of serum creatinine (Cr) alone in estimating glomerular filtration rate (GFR); current GFR estimating models appear to underestimate renal dysfunction. Newer models incorporating renal biomarkers, such as the Cr-Cystatin C GFR Equation for Cirrhosis appear to estimate measured GFR more accurately. A major change in the diagnostic criteria for HRS based on dynamic serial changes in serum Cr that regard HRS type 1 as a special form of acute kidney injury promises the possibility of earlier identification of renal dysfunction in patients with cirrhosis. The diagnostic criteria of HRS still include the exclusion of other causes of kidney injury. Renal biomarkers have been disappointing in assisting with the differentiation of HRS from prerenal azotemia and other kidney disorders. Serum metabolomic profiling may be a more powerful tool to assess renal dysfunction, although the practical clinical significance of this remains unclear. As a result of the difficulties of assessing renal function in cirrhosis and the varying HRS diagnostic criteria and the rigor with which they are applied, the precise incidence and prevalence of HRS is unknown, but it is likely that HRS occurs more commonly than expected. The pathophysiology of HRS is rooted firmly in the setting of progressive reduction in renal blood flow as a result of portal hypertension and splanchnic vasodilation. Progressive marked renal cortical ischemia in patients with cirrhosis parallels the evolution of diuretic-sensitive ascites to diuretic-refractory ascites and HRS, a recognized continuum of renal dysfunction in cirrhosis. Alterations in nitrous oxide production, both increased and decreased, may play a major role in the pathophysiology of this evolution. The inflammatory cascade, triggered by bacterial translocation and endotoxemia, increasingly recognized as important in the manifestation of acute-on-chronic liver failure, also may play a significant role in the pathophysiology of HRS. The mainstay of treatment remains vasopressor therapy with albumin in an attempt to reverse splanchnic vasodilation and improve renal blood flow. Several meta-analyses have confirmed the value of vasopressors, chiefly terlipressin and noradrenaline, in improving renal function and reversing HRS type 1. Other interventions such as renal replacement therapy, transjugular intrahepatic portosystemic shunt, and artificial liver support systems have a very limited role in improving outcomes in HRS. Liver transplantation remains the definitive treatment for HRS. The frequency of simultaneous liver-kidney transplantation has increased dramatically in the Model for End-stage Liver Disease era, with changes in organ allocation policies. This has resulted in a more urgent need to predict native kidney recovery from HRS after liver transplantation alone, to avoid unnecessary simultaneous liver-kidney transplantation.

Keywords: Cirrhosis; Cystatin C; Hepatorenal Syndrome; Meta-Analysis; Terlipressin.

Figure 1

Algorithm in the diagnosis and treatment of AKI-HRS for hepatorenal disorders in cirrhosis.^{, -}

Figure 2

Renal vasoconstriction in cirrhosis progresses from main renal artery (hilum), toward interlobar arteries (renal medulla) and finally affects arcuate (junction of renal medulla and cortex) and interlobular arteries (renal cortex). There is an inverse relationship between renal blood flow (RBF) and renal resistive index (RI).^, When RBF decreases, renal RI increases. ^, While patients without ascites and with diuretic-sensitive ascites preserve cortical renal blood, those with diuretic-refractory ascites have a substantial reduction in cortical renal blood flow. ^, Therefore, while there is a renal RI gap between interlobar and cortical arteries in patients with cirrhosis without ascites and with diuretic-sensitive ascites, this RI gap disappears due to an increase in both interlobar and cortical RIs in patients with cirrhosis and diuretic-refractory ascites. Cortical ischemia is considered to be the landmark feature of cirrhosis and diuretic-refractory ascites and HRS.^{, -} (Used with permission of Baylor College of Medicine).

Figure 3

The percentage of adult simultaneous liver-kidney transplants (SLKT) among all adult deceased liver transplants in the US. Since the implementation of MELD score in 2002, there has been a 150% increase in the percentage of adult SLKTs among all adult deceased donor liver transplants in the US; from 4% in 2002 to 10% in 2016. Data are based on Organ Procurement and Transplantation Network data as of January 23, 2017.