Descent of the bladder neck: a urographic finding in denervation of the urethral sphincter in children with myelodysplasia.

The urographic position of the neck of the bladder in relation to the pubic symphysis was correlated with lower motor neuron (LMN) denervation of the urethral sphincter as detected with electromyography in 65 infants and children with myelodysplasia. Descent (prolapse) of the bladder (bladder neck below the upper margin of the pubic symphysis) was present in 30 (46.2%) patients. Prolapse was both more frequent and tended to be more severe in girls. Complete LMN denervation of the urethral sphincter was present in 25 (83.3%) of the 30 patients with prolapse and in only four (11.4%) of 35 with a normally positioned bladder. Conversely, 25 (86.2%) of the 29 patients with complete LMN denervation of the sphincter had prolapse as compared with only five (13.9%) of 36 patients with partial or no LMN denervation of the sphincter. Although not as precise as urodynamic testing, significant descent of the bladder neck is a reliable urographic finding of complete LMN denervation of the external urethral sphincter in infants and children with myelodysplasia.