Evaluation of differential renal function of children with urinary tract infection complicated by hydronephrosis using renal dynamic and static imaging techniques

Abstract

Objective

This study aims to compare differential renal function (DRF) results obtained from Tc-99m DTPA and Tc-99m DMSA scintigraphy in children with urinary tract infection (UTI) combined with varying degrees of hydronephrosis. We evaluate the diagnostic performance of both methods and provide recommendations for selecting individualized imaging strategies based on specific case characteristics.

Methods

A retrospective analysis was conducted on 57 children with UTI combined with ipsilateral hydronephrosis. Clinical data collected included gender, age, urinary ultrasound findings, and results from renal dynamic and static scintigraphy. Hydronephrosis was classified by ultrasound into mild (<15 mm), moderate (15–30 mm), and severe (>30 mm). The kidney volume ratio between the affected and unaffected sides was calculated. DRF percentages for each kidney were separately obtained from both scintigraphy methods, and the deviation in DRF of the affected kidney was calculated. Based on the degree of deviation, results were categorized as normal (<5%), differing (5%–10%), or significantly different (>10%). The non-parametric Mann–Whitney U test was used to compare DRF values between Tc-99m DMSA and Tc-99m DTPA. Spearman correlation analysis assessed the relationship between hydronephrosis and DRF deviation. Receiver operating characteristic (ROC) curves were used to determine diagnostic thresholds and assess the predictive value of renal pelvic and calyceal dilation for DRF deviations.

Results

Among the 57 children, the median DRF of the affected kidney was 50.84% (IQR: 43.24,55.00) by Tc-99m DMSA and45% (IQR: 35.35, 47.95) by Tc-99m DTPA, with the difference being statistically significant (Z = −4.074, p < 0.000). Of these, 34 children had a DRF deviation > 5%, and 16 had a deviation >10%. Positive correlations were observed between DRF deviation and renal pelvic dilation (r = 0.299, p = 0.024), calyceal dilation (r = 0.235, p = 0.078), and kidney volume ratio (r = 4.416, p = 0.001). A renal pelvic dilation >13.5 mm or calyceal dilation >8.8 mm predicted DRF deviations >5% with a sensitivity of 73.5% and 79.4%, respctively. For deviations >10%, a calyceal dilation long axis >23.2 mm yielded a diagnostic specificity of 100%.

Conclusion

Tc-99m DMSA-derived DRF may be affected by the degree of hydronephrosis. In children with UTI combined with hydronephrosis, significant differences in DRF assessment exist between Tc-99m DMSA and Tc-99m DTPA. When renal pelvic dilation exceeds 13.5 mm or calyceal diameter reaches 23.2 mm, Tc-99m DMSA may overestimate renal function. In such cases, Tc-99m DTPA should be considered for more accurate functional evaluation.