Portosystemic shunt ratio
The portosystemic shunt ratio is a measure performed using ultrasound to quantify the abnormal flow of portal venous blood that is shunted away from the hepatic sinusoidal circulation in the context of a congenital portosystemic shunt.
Measurement
The ratio is determined on ultrasound using the following equations:
- portovenous shunt ratio = blood flow volume in shunt vessel / blood flow volume in portal vein
Where blood flow volume is determined by:
- blood flow volume = lumen area x mean velocity
Interpretation
It has been published that shunt ratios of <24-30% do not cause hepatic encephalopathy .