Hepatorenal syndrome

Hepatorenal syndrome refers to a form of acute kidney injury (AKI) caused by changes in renal blood flow regulation due to liver pathology ¹. Although the syndrome occurs mainly in cirrhotic livers it has been reported in patients with acute fulminant liver failure as well ¹.

Epidemiology

The incidence of hepatorenal syndrome in patients with end-stage liver disease is up to 7.6% ².

Clinical presentation

The patient usually has chronic liver disease with cirrhosis. Symptoms may include reduced urine output, and there may or may not be a precipitant (e.g. spontaneous bacterial peritonitis). The signs and symptoms of underlying chronic liver disease may also be present.

The main laboratory finding of hepatorenal syndrome is an acutely elevated serum creatinine level. However, it is difficult to diagnose hepatorenal syndrome based on these non-specific findings alone, instead it is a diagnosis of exclusion after other causes of acute kidney injury have been ruled out ².

Pathology

Hepatorenal syndrome is thought to develop from several pathological processes occurring in the diseased liver. One of these processes is portal hypertension causing bacterial translocation from the gut into the portal system, as well as causing splanchnic and systemic blood vessel dilatation, and the activation of liver chemoreceptors and baroreceptors. The summative effect of these lead to the activation of neurohumoral pathways (e.g. sympathetic nervous system, renin-angiotensin-aldosterone system) which stimulate renal vasoconstriction and reduce blood flow to the kidneys leading to injury ^2,3.

Types

Two types have been identified, based upon how rapid the decline in renal function is ⁵:

• HRS-AKI (previously 'type 1 HRS'): increase in creatinine of two-fold or more, with no resolution after at least two days of diuretic withdrawal and volume expansion with albumin, absence of shock, no current or recent treatment with nephrotoxic drugs, and absence of parenchymal renal disease

  • subtypes:

    • HRS-AKI on HRS-CKD (previously 'type 1 on 2 HRS')

    • HRS-AKI on CKD: CKD is non-HRS due to known structural damage

• non-AKI-HRS (previously 'type 2 HRS'):

  • HRS-AKD: renal dysfunction that does not meet criteria for AKI and lasts <3 months

  • HRS-CKD: eGFR <60 mL/min/1.73m² for ≥3 months in the absence of other structural causes

Radiographic features

Ultrasound 

In cases of hepatorenal syndrome where there is no pre-existing intrinsic renal disease the kidneys should show a normal size and no evidence of atrophy ². Normal appearing kidneys on ultrasound is required for the diagnosis of hepatorenal syndrome according to the Hepatorenal Syndrome-AKI Guidelines produced by the International Club of Ascites ².

Treatment and prognosis

Management is typically supportive with vasopressor and albumin infusions ¹, although management directed at treating a precipitant, if identified, is also important. However, the only definitive treatment for hepatorenal syndrome is liver transplantation ². Hepatorenal syndrome in patients with liver cirrhosis heralds a poor prognosis in the realm of weeks to months ⁴.