1. What is the Resistive Index?

The Resistive Index (RI) is a doppler ultrasound parameter used to assess vascular resistance in various organs, particularly useful in pediatric renal and hepatic doppler studies.

2. How Does the Calculator Work?

The calculator uses the Resistive Index equation:

Where:

• \( PSV \) — Peak Systolic Velocity (cm/s)
• \( EDV \) — End Diastolic Velocity (cm/s)

Explanation: The equation calculates the ratio between the difference of peak systolic and end diastolic velocities to the peak systolic velocity, providing a measure of vascular resistance.

3. Importance of RI Calculation

Details: RI measurement is crucial for evaluating renal perfusion, detecting renal artery stenosis, assessing transplant kidney function, and monitoring various pediatric renal conditions.

4. Using the Calculator

Tips: Enter PSV and EDV values in cm/s obtained from doppler ultrasound measurements. Both values must be valid (PSV > 0, EDV ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: What are normal RI values in children?
A: Normal renal RI in children typically ranges from 0.58 to 0.64, though values may vary slightly with age and measurement technique.

Q2: When is elevated RI concerning?
A: RI values above 0.70 in children may indicate increased renal vascular resistance and require further investigation.

Q3: What factors can affect RI measurements?
A: Heart rate, blood pressure, hydration status, and technical factors like Doppler angle can influence RI values.

Q4: Is RI measurement different in neonates?
A: Yes, neonates may have slightly higher normal RI values (up to 0.75-0.80) that gradually decrease during the first year of life.

Q5: Can RI be used for other organs besides kidneys?
A: Yes, RI is also used in hepatic, splenic, and cerebral Doppler studies, though normal values differ by organ.