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Evaluation of differential renal function of children with urinary tract infection complicated by hydronephrosis
Xiemei Ruan1, Ha Wu1, Zhengguo Chen2
1Department of Nuclear Medicine, Children's Hospital of Fudan University, National Children's Medical Center, Shanghai 201102, China.
Insights
Differential renal function (DRF) in children with urinary tract infection (UTI) and hydronephrosis differs significantly between Tc-99m DMSA and Tc-99m DTPA scans. Tc-99m DMSA may overestimate function in severe hydronephrosis, suggesting Tc-99m DTPA for accurate evaluation.
Area of Science:
- Pediatric Nephrology
- Nuclear Medicine Imaging
- Diagnostic Radiology
Background:
- Urinary tract infections (UTIs) in children can lead to hydronephrosis, impacting renal function assessment.
- Differential renal function (DRF) is crucial for managing pediatric UTIs and hydronephrosis.
- Tc-99m dimercaptosuccinic acid (DMSA) and Tc-99m diethylenetriaminepentaacetic acid (DTPA) are common scintigraphy agents for evaluating renal function.
Purpose of the Study:
- To compare DRF results from Tc-99m DMSA and Tc-99m DTPA scintigraphy in children with UTI and hydronephrosis.
- To evaluate the diagnostic performance of both imaging modalities.
- To provide recommendations for selecting appropriate imaging strategies based on hydronephrosis severity.
Main Methods:
- Retrospective analysis of 57 children with UTI and ipsilateral hydronephrosis.
- Classification of hydronephrosis severity (mild, moderate, severe) based on ultrasound measurements.
- Calculation of DRF using both Tc-99m DMSA and Tc-99m DTPA, and assessment of DRF deviation.
- Statistical comparison of DRF values and correlation analysis with hydronephrosis parameters using Mann-Whitney U, Spearman, and ROC curve analyses.
Main Results:
- Significant differences in median DRF were found between Tc-99m DMSA (50.84%) and Tc-99m DTPA (45%) in affected kidneys (p < 0.000).
- DRF deviation correlated positively with renal pelvic dilation, calyceal dilation, and kidney volume ratio.
- Renal pelvic dilation >13.5 mm or calyceal dilation >8.8 mm predicted DRF deviations >5% with high sensitivity.
Conclusions:
- Tc-99m DMSA-derived DRF can be influenced by the degree of hydronephrosis in children with UTI.
- Significant discrepancies exist in DRF assessment between Tc-99m DMSA and Tc-99m DTPA in this cohort.
- Tc-99m DTPA is recommended for accurate functional evaluation when hydronephrosis is severe (renal pelvic dilation >13.5 mm or calyceal diameter >23.2 mm) to avoid overestimation of renal function by Tc-99m DMSA.
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.
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