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Scintigraphic assessment of lower urinary tract function in children with and without outflow tract obstruction
M J van der Vis-Melsen1, R J Baert, J R Rajnherc
1Department of Nuclear Medicine, Mariastichting Hospital, Haarlem, The Netherlands.
Insights
Radionuclide renography effectively assesses lower urinary tract function in children. This non-invasive method accurately measures urine flow and bladder capacity, aiding in the diagnosis of outflow obstruction.
Area of Science:
- Pediatric Urology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Assessing lower urinary tract function in children is crucial for diagnosing conditions like outflow obstruction.
- Standard renography is a common diagnostic tool, but its extension can provide more detailed functional analysis.
Purpose of the Study:
- To evaluate the utility of an extended radionuclide renography protocol using 123I-hippurate for assessing lower urinary tract function in pediatric patients.
- To introduce and validate the index of urine transport (IUT) as a measure of bladder outflow capability.
Main Methods:
- Nineteen children underwent analysis of lower urinary tract function using extended radionuclide renography with 123I-hippurate.
- Key parameters measured included bladder capacity, voiding and residual volumes, urine flow rates, and flow patterns.
- The index of urine transport (IUT) was calculated as a ratio of urine flow rate to bladder volume.
Main Results:
- In children without outflow obstruction (n=129), 90% exhibited normal urine flow patterns, with 96% showing average IUT ≥ 0.8 and 87% showing maximum IUT ≥ 1.2.
- Children with outflow tract obstruction (n=70) frequently presented with abnormal findings, including low, flat flow patterns and decreased IUT (63%), or sawtooth patterns with varying IUT (15%).
- A subset of obstructed children (20%) showed normal flow patterns and IUT values, highlighting the complexity of diagnosis.
Conclusions:
- Extended radionuclide renography with 123I-hippurate is a valuable, non-invasive method for screening pediatric lower urinary tract function.
- The index of urine transport (IUT) provides a useful quantitative measure of bladder outflow capability.
- This extended renography technique offers advantages over conventional direct urine flow rate recording and integrates well with existing urological investigations.
Abstract:
Analysis of lower urinary tract function with an extension of standard renography with 123I-hippurate was carried out in 199 children. Maximum bladder capacity, voiding and residual bladder volumes, average and maximum urine flow rates and urine flow patterns were estimated. The index of urine transport (IUT), representing the relationship between urine flow rate and bladder volume, was introduced as a measure of outflow capability. Of 129 children without evidence of outflow obstruction, 90% had a normal urine flow pattern; in 96% the average IUT was 0.8 or higher and in 87% the maximum IUT was 1.2 or higher. A sawtooth-shaped pattern with both normal and abnormal IUT values was observed in 10% of these children. In 63% of the children with outflow tract obstruction there was a low, flat urine flow pattern together with decreased IUT values. A sawtooth-shaped pattern with varying IUT values was observed in 15%, whereas in 20% the urine flow pattern and IUT values were normal. This extension of standard radionuclide renography as a method of screening lower urinary tract function is recommended. It is at least as good as conventional direct urine flow rate recording, it has the advantage of being non-invasive and it is also part of an established urological investigation.