From the Guidelines
The Hepatic artery Resistive Index (RI) on Doppler ultrasound is abnormal if it is less than 0.55.
Interpretation of Hepatic Artery RI
- A Resistive Index (RI) of less than 0.55 is considered abnormal and may indicate the presence of liver vascular malformations (VMs) or other hepatic artery abnormalities 1.
- The RI is used in conjunction with other Doppler ultrasound parameters, such as peak flow velocity and hepatic artery diameter, to assess the severity of liver VMs.
- The grading of liver VMs based on Doppler ultrasound findings, including RI, is as follows:
- 0+: RI less than 0.55, peak flow velocity greater than 80 cm/sec, and/or peripheral hepatic hypervascularization
- 1-4: Increasing severity of liver VMs, with RI less than 0.55 and other abnormal Doppler ultrasound findings 1.
Clinical Significance
- An abnormal RI may indicate the need for further evaluation and management of liver VMs or other hepatic artery abnormalities.
- The diagnosis and grading of liver VMs using Doppler ultrasound, including RI, is important for the management of patients with hereditary hemorrhagic telangiectasia (HHT) and other conditions affecting the liver 1.
From the Research
Interpretation of Hepatic Artery Resistive Index (RI)
The Hepatic Artery Resistive Index (RI) is a parameter used in Doppler ultrasound to assess the resistance to blood flow in the hepatic artery. The interpretation of RI values can vary depending on the clinical context and the presence of certain conditions.
- A high RI (close to 1) may indicate hepatic arterial vasospasm, stenosis, or thrombosis 2, 3.
- A low RI (< 0.55) may be associated with an increased incidence of hepatic artery thrombosis and decreased graft survival in liver transplant recipients 4.
- An elevated RI (> 0.74) may be a predictor of fulminant hepatic failure in patients with acute viral hepatitis 5.
- A high RI immediately after liver transplantation may be related to older donor age and prolonged preservation time, but it does not seem to have significant clinical repercussions or prognosis implications for early and long-term follow-up 6.
Clinical Implications
The clinical implications of RI values can vary depending on the specific condition being assessed. For example:
- In liver transplant recipients, a low RI (< 0.55) on the first post-operative day may be associated with an increased risk of hepatic artery thrombosis and decreased graft survival 4.
- In patients with acute viral hepatitis, an elevated RI (> 0.74) may be a predictor of fulminant hepatic failure 5.
- In patients with suspected hepatic arterial vasospasm, a high RI (close to 1) may respond to vasodilator therapy 2.