renal arterial resistance index =
= (100 * (1 - ((minimum diastolic blood flow velocity in cm/sec) / (peak systolic blood flow velocity in cm/sec))))
The reported value is usually the average value of 2-3 measurements.
where:
• The index is independent of the beam to vessel angle.
• The index is based on measurement of 2 distinct points on the arterial waveform.
• Measurement assumes that there is no reverse flow component.
• The Doppler waveform may be affected by factors other than resistance to blood flow.
• The index can be applied to the main renal artery or to segmental arteries.
Interpretation:
• In renal transplants a renal arterial resistance index measured 3 or more months after the transplant that was >= 80 was associated with poor survival of the allograft and the patient.
|
Renal Arterial Resistance Index
|
need for dialysis at 5 years after transplant
|
patient survival at 5 years after transplant
|
|
< 80
|
10%
|
90%
|
|
>= 80
|
60%
|
43%
|
from Figure 2, page 123, Radermacher et al (2003)
