The Systemic and Splanchnic Circulations

In liver cirrhosis, splanchnic and systemic hemodynamic abnormalities are common in patients with portal hypertension. Portal hypertension leads to progressive vasodilatation of the arteries of the splanchnic and systemic circulations, a key event which in turn exacerbates portal hypertension by increasing splanchnic blood flow. Since portal hypertension is central to the development of complications observed in patients with liver disease, the mechanisms underlying this arterial vasodilatation have been an important area of investigation. While nitric oxide (NO) has been shown to be the primary vasodilator molecule, other molecules are also involved in the complex mechanisms of arterial vasodilatation in the systemic and particularly splanchnic circulation. In recent years, it has been suggested that sensory mechanisms in the intestinal microcirculation prompt the initiation of vasodilatation and the progression of portal hypertension. This chapter will summarize the etiology and molecular mechanisms of arterial vasodilatation observed in the intestinal, splanchnic, and systemic circulations in portal hypertension with cirrhosis.