Urodynamics: a noninvasive screening of lower urinary tract function in children with radioisotopes.

A noninvasive intravenous assessment of lower urinary tract function with 123I-hippurate was carried out in 129 children without suspicion of lower urinary tract outflow pathology. Without increasing the radiation burden standard renography was extended by lower urinary tract function analysis in the same session. The maximum bladder capacity, voiding and residual bladder volumes, average and maximum urine flow rates were calculated and the relation between the urine flow rate and bladder volume expressed as the index of urine transport (IUT). This index seems to be a much more reliable standard than isolated measurements of urine flow rates and bladder volumes in screening lower urinary tract function. Three different urine flow patterns were recognized: a single sharp peak (in 70%) and a biphasic curve (in 20%) were considered to be normal. A sawtooth-shaped pattern, observed in 10% of the children, may be caused by detrusor malfunction. The prolonged time necessary for this more extensive analysis of the lower urinary tract is well compensated by the additional information gained.