Why does hepatorenal syndrome (HRS) develop in patients with in cirrhosis?

Updated: Oct 16, 2017
  • Author: Deepika Devuni, MD; Chief Editor: BS Anand, MD  more...
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Answer

Various theories have been proposed to explain the development of HRS in cirrhosis. The 2 main theories are the arterial vasodilation theory and the hepatorenal reflex theory. The former theory not only describes sodium and water retention in cirrhosis, but also may be the most rational hypothesis for the development of HRS. Splanchnic arteriolar vasodilatation in patients with compensated cirrhosis and portal hypertension may be mediated by several factors, the most important of which is probably NO. In the early phases of portal hypertension and compensated cirrhosis, this underfilling of the arterial bed causes a decrease in the effective arterial blood volume and results in homeostatic/reflex activation of the endogenous vasoconstrictor systems.

Activation of the RAAS and SNS occurs early with antidiuretic hormone secretion, a later event when a more marked derangement in circulatory function is present. This results in vasoconstriction not only of the renal vessels, but also of the vascular beds of the brain, muscle, spleen, and extremities. The splanchnic circulation is resistant to these effects because of the continuous production of local vasodilators such as NO.

In the early phases of portal hypertension, renal perfusion is maintained within normal or near-normal limits as the vasodilatory systems antagonize the renal effects of the vasoconstrictor systems. However, as the liver disease progresses in severity, a critical level of vascular underfilling is achieved. Renal vasodilatory systems are unable to counteract the maximal activation of the endogenous vasoconstrictors and/or intrarenal vasoconstrictors, which leads to uncontrolled renal vasoconstriction. Support for this hypothesis is provided by studies in which the administration of splanchnic vasoconstrictors in combination with volume expanders results in improvement in arterial pressure, RPF, and the GFR.

The alternative theory proposes that renal vasoconstriction in HRS is unrelated to systemic hemodynamics but is due to either a deficiency in the synthesis of a vasodilatory factor or a hepatorenal reflex that leads to renal vasoconstriction. Evidence points to the vasodilation theory as a more tangible explanation for the development of HRS.


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