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Utility of the resistance index ratio in differentiating obstructive from nonobstructive hydronephrosis in children
1Department of Radiology, St. Mary's Hospital, The Catholic University of Korea, Seoul, South Korea.
Insights
The resistance index ratio (RIR) effectively distinguishes obstructive from nonobstructive upper urinary tract dilation in children. A RIR cutoff of 1.10 offers high accuracy for diagnosing and monitoring pediatric hydronephrosis.
Area of Science:
- Pediatric Nephrology
- Diagnostic Imaging
- Urology
Background:
- Upper urinary tract dilatation in children can be obstructive or nonobstructive, requiring accurate differentiation for appropriate management.
- Duplex Doppler sonography is a common imaging modality in pediatric urology.
Purpose of the Study:
- To evaluate the effectiveness of the resistance index ratio (RIR) in differentiating between obstructive and nonobstructive upper urinary tract dilatation in pediatric patients.
- To establish a diagnostic threshold for RIR in pediatric hydronephrosis.
Main Methods:
- Prospective evaluation of 23 children (7 days-14 years) with unilateral dilated collecting systems using duplex Doppler sonography.
- Measurement of intrarenal artery resistance index (RI) and calculation of the RIR.
- Comparison with 96 normal kidneys in 48 controls and correlation with scintigraphy/surgical findings.
Main Results:
- The mean RIR was significantly higher in obstructed kidneys (1.16+/-0.04) compared to nonobstructed dilated kidneys (1.04+/-0.04).
- Surgical correction of ureteropelvic junction obstruction led to a significant decrease in RIR.
- An RIR cut-off value of >= 1.10 demonstrated high sensitivity (92%) and specificity (97%) for diagnosing obstruction.
Conclusions:
- The resistance index ratio (RIR) is a valuable, non-invasive parameter for differentiating obstructive from nonobstructive hydronephrosis in children.
- An RIR cut-off of 1.10 is effective for the evaluation and follow-up of unilateral obstructive hydronephrosis in pediatric patients.
Purpose:
We assessed the utility of the resistance index ratio (RIR) in distinguishing between obstructive and nonobstructive upper urinary tract dilatation in children.
Methods:
Twenty-three children (7 days-14 years old) with unilateral dilated collecting systems and a contralateral normal kidney were prospectively evaluated by duplex Doppler sonography. We measured the resistance index (RI) of the intrarenal arteries and calculated the RIR. Ninety-six normal kidneys in 48 controls were also evaluated.
Results:
Twelve kidneys were proved to be obstructed at the ureteropelvic junction, and 11 were found by renal scintigraphy with furosemide and/or by surgery to have nonobstructive dilatation. The mean RIR differed significantly between the obstructed and dilated nonobstructed kidneys (1.16+/-0.04 versus 1.04+/-0.04, respectively; p < 0.01). After surgical correction of ureteropelvic junction obstruction, the obstructed kidneys showed significant drops in the RIR (1.18+/-0.03 to 1.07+/-0.03, p < 0.01). The RIR showed no statistically significant relationship with age (r = -0.268, p > 0.01); however, the RI declined with increasing age (r= -0.414, p < 0.01). An RIR cut-off value of > or = 1.10 provided a good discriminatory level, resulting in a sensitivity of 92%, a specificity of 97%, a positive predictive value of 85%, and a negative predictive value of 97%.
Conclusions:
An RIR cut-off value of > or = 1.10 appears to be an effective parameter for evaluation and follow-up of unilateral obstructive hydronephrosis in children.