Normal kidney RI is less than which value?

• A. Less than 6
• B. Less than 7.5-8
• C. Less than 9
• D. Less than 7.0

Answer: (B)

The main idea is that the kidney Resistive Index (RI) is a measure of intrarenal vascular resistance on Doppler ultrasound, and there is a conventional upper limit that is considered normal. In this context, a normal RI is typically cited as being less than about 7.5 to 8. Values below that are within normal limits, while values at or above this range suggest increased intrarenal resistance that may warrant further evaluation.

Choosing the upper normal cutoff as 7.5–8 makes sense because it defines the threshold beyond which the resistance is considered not normal, rather than simply noting that some lower values are acceptable. The other options either reflect values that are not the commonly used upper limit (for example, 9 would be outside normal) or are simply lower cutoffs that are still within normal range but don’t specify the standard upper boundary.