Estimation of differential renal function in unilateral hydronephrotic kidneys with asymmetrical renal area ratio: Comparison of classical and unit area corrected methods

Document Type : Original Article

Authors

Department of Nuclear Medicine, Sindh Institution of Urology and Transplantation, Karachi, Pakistan

Abstract

Introduction: Differential renal function calculation plays an important role in surgical decisions in hydronephrotic kidneys, which may show false-positive or false-negative results owing to the asymmetrical renal area in hydronephrotic kidneys. The disparity between the visual and quantitative estimations of renal function can complicate decision making for renal interventions at the optimal time. This study was designed to evaluate whether correcting the differential renal function (DRF) estimation according to kidney unit area can be a more valuable predictor of the functional status of a hydronephrotic kidney than the classical geometric mean method.
Methods: Tc-99m Dimercaptosuccinic acid ([99mTc]Tc-DMSA) scans and ultrasonography finding of 524 patients with unilateral hydronephrosis due to urinary tract obstruction were reviewed. Differential renal function estimated by both classical geometric mean and unit area corrected method were compared. The correlations of the differential renal function values with the visual classification and the hydronephrosis grades were assessed.
Results: The mean Differential renal function by the classical geometric mean and the unit area corrected method of the hydronephrotic kidneys was 41.2%±12.3 and 36.6%±9.9 respectively, with mean difference of 4.6±7.7% (p<0.001). With increasing hydronephrosis grade, differential renal function decreased significantly by the unit area corrected method (p<0.001).
Conclusion: Our results suggest that differential renal function estimation by the unit area corrected method is more reliable than by the classical geometric mean method in unilateral enlarged hydronephrotic kidney to avoid misinterpretation due to over-estimation of renal function.

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References

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