How to Perform Renal Blood Flow Measurements

  1. Obtain a transgastric SAX mid-papillary
  2. Turn the probe 90-270° and advance 4-5 cm
  3. As you turn you may visualize the left kidney (central echogenic pelvis and hypoechogenic peripheral cortex)
  4. If by turning to the left you visualize the descending aorta, turn the probe back to the right about 90° and find the left kidney
  5. Zoom in the left kidney, apply color flow Doppler (decrease the scale and increase color flow gain to visualize blood flow through the kidney)
  6. Apply PW Doppler
  7. Measure peak systolic velocity (S) and minimum diastolic velocity (D)
  8. Renal resistivity index (RRI) = (S-D)/S
  9. Perfect alignment of the PW Doppler beam with the blood flow is not necessary as we are not interested in velocities but in the ratio of these velocities.
Renal Bloodflow ultrasound