Scintigraphic assessment of lower urinary tract function in children with and without outflow tract obstruction.

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.