Supranormal differential renal function in unilateral hydronephrotic kidney: insights from functional MR urography

Area of Science:

• Medical Imaging
• Pediatric Urology
• Renal Physiology

Background:

• Unilateral hydronephrosis can affect differential renal function (DRF) assessment.
• Functional MR urography (fMRU) is a tool for evaluating kidney function.
• Distinguishing true hyperfunction from volume-related changes is crucial.

Purpose of the Study:

• To retrospectively evaluate supranormal differential renal function (DRF) in unilateral hydronephrotic kidneys.
• To assess kidney function using functional MR urography (fMRU).
• To investigate the relationship between kidney volume and DRF in pediatric hydronephrosis.

Main Methods:

• Retrospective analysis of patients undergoing fMRU (2008-2011).
• DRF measurement using area under the curve and Rutland-Patlak plot.
• Analysis of glomerular DRF per unit volume and kidney volumes, compared to nomograms.

Main Results:

• Three pediatric patients with ureteropelvic junction obstruction were included.
• Glomerular DRF per unit volume was slightly elevated in dilated kidneys but within normal limits (<55%).
• Dilated kidney volumes were significantly increased (≥55%), while non-dilated kidneys had normal volumes.

Conclusions:

• Dilated kidneys in this cohort did not exhibit hyperfunction; non-dilated kidneys were not hypofunctioning.
• Apparent supranormal DRF in dilated kidneys may be attributed to kidney volume asymmetry.
• Higher DRF per unit volume, within physiological ranges, contributes to this observation.