Contradictory supranormal nuclear renographic differential renal function: fact or artifact?

Area of Science:

• Pediatric Nephrology
• Nuclear Medicine
• Urology

Background:

• Nuclear renography using diethylenetriaminepentaacetic acid (DTPA) has shown paradoxical supranormal differential renal function in unilateral hydroureteronephrosis.
• This finding contradicts expected renal function distribution in affected kidneys.

Purpose of the Study:

• To determine if supranormal differential function observed with DTPA renography reflects true hyperfunction in unilateral hydroureteronephrosis.
• To compare DTPA findings with dimercaptosuccinic acid (DMSA) renography results in pediatric patients.

Main Methods:

• Retrospective analysis of 16 pediatric patients (<1 year old) with unilateral hydronephrosis and DTPA differential function ≥53%.
• Comparison of DTPA differential renal function with DMSA differential renal function in the same patient cohort.
• Statistical analysis to compare DTPA and DMSA results and assess DMSA against an expected 50% mean.

Main Results:

• All 16 patients showed lower DMSA differential function (mean 51.1%) compared to their DTPA values (mean 58.3%, p < 0.0001).
• DMSA differential function was not significantly different from the expected 50% mean (p = 0.48).
• DTPA's supranormal differential function findings were not supported by DMSA results.

Conclusions:

• DTPA renography may overestimate differential renal function in pediatric unilateral hydroureteronephrosis.
• DMSA renography appears to be a more reliable method for assessing differential renal function in this condition.
• Caution is advised when interpreting DTPA results in hydronephrosis until its limitations are better understood.