Influence of early furosemide injection on the split renal function

Area of Science:

• Nuclear Medicine
• Pediatric Nephrology
• Diagnostic Imaging

Background:

• Split renal function (SRF) is a key parameter in renography, typically calculated when tracer has not escaped the kidney.
• The timing of furosemide administration in diuretic renography (F0 vs. F+20) may impact SRF accuracy.
• Early tracer escape during furosemide renography could lead to underestimation of SRF.

Purpose of the Study:

• To investigate if simultaneous furosemide administration (F0 test) accelerates tracer escape compared to delayed administration (F+20 test).
• To assess the impact of early tracer escape on SRF calculations using different methods.
• To determine the optimal method for calculating SRF when furosemide is given simultaneously with the tracer.

Main Methods:

• Retrospective analysis of 36 children who underwent both F0 and F+20 diuretic renography.
• SRF calculated using integral method, slope method, and Rutland-Patlak plot based on 1-2 min background-corrected renal activity.
• Analysis of T(max) values to evaluate early tracer escape in F0 vs. F+20 tests.

Main Results:

• The F0 test showed a T(max) < 3 min in 19 kidneys, indicating accelerated renal transit.
• A tendency to underestimate SRF was observed in the F0 test for kidneys with T(max) < 3 min, particularly with the slope method (P=0.03).
• The integral method showed no significant difference in SRF calculation between F0 and F+20 tests (P=0.5).

Conclusions:

• Simultaneous furosemide administration with the tracer accelerates renal transit, potentially causing SRF underestimation.
• The integral method appears more robust for SRF calculation when furosemide is administered simultaneously.
• Clinical practice should consider the chosen renography method's susceptibility to early tracer escape.