hepatic arterial resistive index
The resistive index (RI) is the commonest Doppler parameter used for hepatic arterial evaluation. The usual range in normal, as well as post-transplant individuals, is between 0.55 and 0.8.
It is measured by:
Resistive index (RI) = (peak systolic velocity - end-diastolic velocity)/peak systolic velocity
Hepatic arterial resistive index is most often assessed during the evaluation of a liver transplant. In this setting, a low RI is usually more specific for disease than a high RI (the opposite situation from a renal transplant) .
Low RI: more specific for disease in a liver transplant, a low RI may result from:
- partial upstream arterial occlusion
- steno-occlusive disease of the transplant hepatic artery
- celiac artery stenosis
- median arcuate ligament syndrome
- peripheral vascular shunts (arteriovenous or arterioportal)
- hepatic arteriovenous malformations in the hereditary hemorrhagic telangiectasia syndrome
- portal hypertension
High RI: less specific for disease in a liver transplant, a high RI may result from:
- microvascular compression or disease
- chronic hepatocellular disease
- transplant rejection
- hepatic venous congestion
- chronic congestive hepatopathy
- nonocclusive hepatic artery hypoperfusion syndrome
- physiologic
- postprandial state
- advanced patient age
- may transiently elevate within 72 hours after transplant
A high RI can be classified into four types :
- type I: RI >0.80 with continuous blood flow in the diastolic phase
- type II: RI = 1, complete absence of the diastolic signal and preserved systolic velocity
- type III: absence of diastolic signal and diminished systolic velocity
- type IV: undetectable Doppler flow
Siehe auch:
