Urodynamic characteristics of neurogenic bladder in newborns with myelomeningocele and refinement of the definition of bladder hostility: Findings from the UMPIRE multi-center study.

Introduction: Infants with myelomeningocele are at risk for chronic kidney disease caused by neurogenic bladder dysfunction. Urodynamic evaluation plays a key role to risk stratify individuals for renal deterioration.

Objective: To present baseline urodynamic findings from the Urologic Management to Preserve Initial Renal function for young children with spina bifida (UMPIRE) protocol, to present the process that showed inadequacies of our original classification scheme, and to propose a refined definition of bladder hostility and categorization.

Study Design: The UMPIRE protocol follows a cohort of newborns with myelomeningocele at nine children's hospitals in the United States. Infants are started on clean intermittent catheterization shortly after birth. If residual volumes are low and there is no or mild hydronephrosis, catheterization is discontinued. Baseline urodynamics are obtained at or before 3 months of age to determine further management. Based on protocol-specific definitions, urodynamic studies were reviewed by the clinical site in addition to a central review team; and if necessary, by all site urologists to achieve 100% concurrence.

Results: We reviewed 157 newborn urodynamic studies performed between May 2015 and September 2017. Of these 157 infants, 54.8% were boys (86/157). Myelomeningocele closure was performed in-utero in 18.4% (29/157) and postnatally in 81.5% (128/157) of newborns. After primary review, reviewers agreed on overall bladder categorization in 50% (79/157) of studies. Concurrence ultimately reached 100% with further standardization of interpretation. We found that it was not possible to reliably differentiate a bladder contraction due to detrusor overactivity from a volitional voiding contraction in an infant. We revised our categorization system to group the "normal" and "safe" categories together as "low risk". Additionally, diagnosis of detrusor sphincter dyssynergia (DSD) with surface patch electrodes could not be supported by other elements of the urodynamics study. We excluded DSD from our revised high risk category. The final categorizations were high risk in 15% (23/157); intermediate risk in 61% (96/157); and low risk in 24% (38/157).

Conclusion: We found pitfalls with our original categorization for bladder hostility. Notably, DSD could not be reliably measured with surface patch of electrodes. The effect of this change on future renal outcomes remains to be defined.