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. 1998 Feb;42(2):276–282. doi: 10.1136/gut.42.2.276

The relationship between intrahepatic portal systemic shunts and microsphere induced portal hypertension in the rat liver

X Li 1, I Benjamin 1, B Alexander 1
PMCID: PMC1726987  PMID: 9536955

Abstract

Background—Portal hypertension is associated with gross haemodynamic disturbances characterised by high cardiac output, low peripheral vascular resistance, increased splanchnic blood flow, and portal systemic shunting. 
Aims—To study the relationship between intrahepatic portal systemic shunts and microsphere induced portal hypertension in the rat liver. 
Methods—Different sized microspheres were sequentially injected into the portal vein of male Wistar rats. 
Results—Steady state portal venous pressure was increased by 102.2 (35.6)% (14.9 (3.6) mm Hg) and 272.3 (78.0)% (24.0 (2.2) mm Hg) above the basal pressure following sequential injections of 15 and 80 µm diameter microspheres, respectively. Sequential injection of 15, 40, and 80 µm diameter microspheres in either ascending or descending order of size did not generate further increases in portal venous pressure. A single injection of 1.8× 105 80 µm microspheres consistently produced a steady state portal venous pressure of 19.0 (1.3) mm Hg but did not approach the much higher value of 36.6 (43.2) mm Hg measured during clamping of the portal vein. These data indicate that the opening of patent intrahepatic shunts was responsible for the reduced pressures observed during microsphere injections and further evidence for this was provided by the location of microspheres in the pulmonary vascular bed. The elevation in portal venous pressure achieved by microsphere injections was not significantly different to that produced in rats subjected to partial portal vein ligation (20.7(0.5) mm Hg, p>0.05). Wedged hepatic venous pressure decreased from 6.7 (0.7) to 3.0 (0.6) mm Hg following injection of 80 µm microspheres, suggesting a decrease in total hepatic blood flow. Conversely, injection of 15 µm microspheres induced an increase in wedged hepatic venous pressure from 7.0 (1.0) mm Hg to 12.4(1.8) mm Hg, indicating a localised redistribution of blood flow at the presinusoidal level of the portal venous vascular network and increased intrahepatic shunt flow. 
Conclusion—It is suggested that there may be a protective pathophysiological role for these shunts when the liver is subjected to changes which induce acute portal hypertension. 



Keywords: portal hypertension; intrahepatic shunts; rat liver; hepatic blood flow

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Figure 1 .

Figure 1

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Portal venous pressure (PVP) and wedged hepatic venous pressure (WHVP) recordings from group 1 during intraportal injections of 15 µm diameter microspheres and subsequent portal vein occlusion (PVO). 


Figure 2 .

Figure 2

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Changes in portal venous pressure (PVP) during intraportal microsphere injections. *p<0.05, **p<0.01, Student's unpaired t test, group 2 versus group 1. 


Figure 3 .

Figure 3

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Changes in portal venous pressure (PVP) during intraportal microsphere injections. **p<0.01, Student's unpaired t test, group 4 versus group 3. 


Figure 4 .

Figure 4

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Systemic blood pressure (Syst BP), portal venous pressure (PVP), wedged hepatic venous pressure (WHVP), and splenic pulp pressure (SP) measurements after two aliquots of 80 µm diameter microspheres (group 5) were injected continuously into the portal vein. The portal venous pressure was elevated to a steady state value of 19.0 (1.3) mm Hg 150 minutes after injection. However, total occlusion of the portal vein at the liver hilus produced a further dramatic increase in portal venous pressure (PVO) which again suggested that not all the intrahepatic shunts had been occluded. 


Figure 5 .

Figure 5

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Histological sections showing (A) 15, 40, and 80 µm spheres lodged in liver (group 3, original magnification ×10), (B) 15 µm spheres lodged in lung (group 4, original magnification ×40), and (C) 80 µm spheres lodged in lung (group 2, original magnification ×16). 


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