Portal Hypertension Flashcards
Two general concepts that result in an increase in portal hypertension (PH).
- Increase in venous resistance
- Increase in portal venous flow
(pressure = resistance x flow)
Most common cause of portal hypertension.
Cirrhosis - intrahepatic PH
leading cause of increased resistance in hepatic vasculature
Most common cause of pre-sinusoidal PH.
Schistosomiasis (S. mansoni)
How does cirrhosis lead to intrahepatic PH?
- Structural: fibrosis of the sinusoids causes blood to back up in the liver.
- Functional: active vasoconstriction due to release of mediators from the liver and decrease in Nitric Oxide release.
How does cirrhosis also lead to an increase in NO which actually causes worse PH?
Cirrhosis causes a drop in NO release inside the liver vasculature. But this triggers an upstream release of NO in the extra-hepatic portal vessels increasing blood flow into the “plugged up” liver. One of the component of the PH equation is “flow” and this increases flow into the liver.
Describe the effect of Hyperdynamic Circulation caused by cirrhosis.
- Cirrhosis leads to PH
- Portal venous dilation occurs due to increased NO release
- Increased portal blood volume leads to decreased arterial blood volume
- Decreased arterial blood volume is sensed by arterial baroceptors and the macula densa in the kidneys
5 Renin-Ag-Aldosterone system is activated to increase sodium and chloride and water absorption - Leads to overall increased body fluid volume which increases flow in the portal system.
Hepatic Venous Pressure Gradient (HVPG) required for varices to form.
> 12 mmHg
How is HVPG calculated?
HVPG = WHVP - FHVP
WHVP: wedged hepatic venous pressure, measureed by “wedging” a balloon catheter into the hepatic sinusoids and inflating to record pressure.
FHVP: free hepatic venous pressure, measured by deflating the balloon and recording the pressure in the sinusoid.
What HVPG would be expected in Pre-sinusoidal PH?
Normal (3-5mmHg)
-blockage or congestion occurs proximal to the site of measurement (sinusoids)
What HVPG would be expected in sinusoidal PH?
Elevated
-disease occurs within the site of measurement (sinusoids)
What HVPG would be expected in Post-sinusoidal PH?
Elevated
-similar to sinusoidal PH
What HVPG would be expected in Post-Hepatic PH?
May appear normal
-both WHVP and FHVP may be elevated and yield a 3-5mmHg difference
What are 3 predictors of variceal hemorrhage?
- Varix size (larger is worse)
- Red Signs (a red wale sign is a red streak along a varix seen on endoscopy)
- Child-Pugh Class B or C (used to assess prognosis of chronic liver disease)
Higher tension on a varix will increase its chance to rupture. What factors account for the tension?
T = tp x r/w
tp - transmural pressure: produced from within the varix and from the esophagus.
r - radius of varix: larger varix is more likely to rupture
w - width of varix wall: thicker wall is stronger and decreases chance of rupture
Which factor that contributes to tension is targeted by physicians to decrease likelihood of rupture?
Transmural pressure:
Portal venous pressure can be influenced by medication and a decrease in portal pressure will decrease tp.