Renal transit time with MR urography in children

Area of Science:

• Pediatric Radiology
• Urology
• Medical Imaging

Background:

• Obstructive uropathy is a common condition in children requiring accurate diagnosis.
• Conventional imaging methods may have limitations in assessing renal function and obstruction.
• Dynamic contrast-enhanced MR urography offers a non-invasive approach to evaluate urinary tract dynamics.

Purpose of the Study:

• To prospectively evaluate dynamic contrast-enhanced MR urography for measuring renal transit time (RTT).
• To assess the utility of RTT in identifying obstructive uropathy in pediatric patients.
• To compare MR urography-derived RTT with nuclear medicine renography findings.

Main Methods:

• 126 children with suspected hydronephrosis underwent conventional and dynamic contrast-enhanced MR urography.
• A 3D sequence tracked contrast agent passage to define RTT.
• Inter- and intraobserver variability was assessed using Bland-Altman plots.
• ROC analysis compared MR urography RTT with nuclear medicine renography in 30 children.

Main Results:

• Kidneys were classified as normal (RTT ≤ 245s), equivocal (245s < RTT ≤ 490s), or obstructed (RTT > 490s).
• High inter- and intraobserver agreement demonstrated technique robustness and reproducibility.
• MR urography and diuretic renal scintigraphy showed good agreement (mean AUC = 0.90).

Conclusions:

• Renal transit time (RTT) measurement via dynamic contrast-enhanced MR urography is a reliable method.
• RTT effectively differentiates normal from obstructed and partially obstructed kidneys.
• This technique complements morphologic imaging for diagnosing pediatric obstructive uropathy.