AGE-RELATED BLADDER CAPACITY AND BLADDER CAPACITY GROWTH IN CHILDREN WITH MYELOMENINGOCELE

Purpose: Currently the relationship between bladder capacity and age i n children with myelomeningocele is inadequately understood, such that nomograms derived from neurologically normal children are inappropria tely applied to the myelodysplastic population. The aim of the present study was to evaluate age related bladder capacity and bladder capaci ty growth in children with myelomeningocele, and compare them to those of age matched, neurologically intact children.Materials and Methods: Bladder capacity was determined by cystometrography in children with myelodysplasia. Regression analysis was used to derive a relationship between bladder capacity and patient age. Data were stratified by sphi ncter activity, bladder sensation and uninhibited contractions, and re gression analysis was repeated. To evaluate serial growth change in bl adder capacity divided by time yielded a yearly bladder capacity growt h rate in patients who underwent 2 cystometrograms done at least 3 mon ths apart before age 9 years. Results: A total of 506 children satisfi ed study inclusion criteria. Bladder capacity (BC) was related to age for the first 9 years by the linear equation, BC = 24.5 (age) + 62. Th is equation is approximately 25% less steep than published age related bladder capacity in neurologically intact children using the formula, 32 (age) + 73. After data stratification bladder capacity in children with sphincter activity, bladder sensation or no uninhibited contract ions approached that of neurologically intact children. In contrast, c hildren without sphincter activity or bladder sensation, or with uninh ibited contractions had markedly smaller age related bladder capacity. Bladder capacity growth in the subgroup of 55 children in whom 2 cyst ometrograms were performed at least 3 months apart before age 9 years confirmed a mean gain in capacity of 24 cc per year. Conclusions: Norm al bladder capacity in children with myelodysplasia is approximately 2 5% less than in age matched, neurologically intact children. The bladd er grows approximately 24 cc per year until age 9 years. When there is failure to store urine, bladder capacity is much smaller, while child ren with good storage features may attain the bladder capacity expecte d of age matched, neurologically intact children.