What is the normal resistive index (RI) value for the kidney?

What is the normal resistive index (RI) value for the kidney?

• A. 0.7-0.9
• B. <0.7
• C. 0.9-1.1
• D. 0.0-0.5

Answer: (B)

Renal resistive index reflects the resistance to blood flow in the intrarenal arteries. It’s calculated as (PSV − EDV) divided by PSV, giving a value between 0 and 1. In a healthy kidney, diastolic flow is preserved, so the RI stays in a relatively low range, typically about 0.5 to 0.7. Therefore, a normal RI value is less than 0.7. When RI rises above this threshold, it suggests increased downstream resistance from conditions such as parenchymal disease, obstruction, or transplant-related issues, which is why values well above 0.7 are considered abnormal.

Renal resistive index reflects the resistance to blood flow in the intrarenal arteries. It’s calculated as (PSV − EDV) divided by PSV, giving a value between 0 and 1. In a healthy kidney, diastolic flow is preserved, so the RI stays in a relatively low range, typically about 0.5 to 0.7. Therefore, a normal RI value is less than 0.7. When RI rises above this threshold, it suggests increased downstream resistance from conditions such as parenchymal disease, obstruction, or transplant-related issues, which is why values well above 0.7 are considered abnormal.