Neurogenic bladder affects the vast majority of patients with spina bifida and is a major cause of end stage renal disease in this population.¹ A foundational objective in the urologic care of spina bifida patients is to prevent renal deterioration through close surveillance of bladder dynamics. Guidelines for urologic screening and management of neurogenic bladder for the prevention of renal disease have been published by groups such as the European Association of Urology/European Society of Paediatric Urology and the Spina Bifida Association.^2,3 However, urologic guidelines lack level 1 evidence and are based largely on expert opinion. Gaps remain in our understanding of ideal screening protocols to predict renal deterioration, and significant variability exists in the management of neurogenic bladder in spina bifida patients. Ideal protocols for bladder surveillance continue to be debated as practices vary among institutions as well as among individual pediatric urologists.

Many pediatric urologists use routine renal bladder ultrasound (RBUS) with or without voiding cystourethrogram (VCUG) to guide the frequency of urodynamic studies (UDS) to elucidate bladder characteristics that may lead to renal deterioration. Particular variability exists in the use of VCUG in routine screening of neurogenic bladder.⁴ To better understand which RBUS and VCUG findings may predict higher risk bladder characteristics on UDS, we aimed to study the relationship between these findings with UDS detrusor leak point pressures (DLPP) and end filling pressures (EFP).⁵

We retrospectively identified patients with spina bifida at a single institution who underwent at least 1 UDS from 2015 to 2021. We included patients up to 18 years of age who had a RBUS and/or VCUG performed within 6 months of the UDS. Patients who had undergone augmentation cystoplasty prior to these studies were excluded. We also excluded patients who underwent urologic interventions such as initiation of clean intermittent catheterization or anticholinergics during the interim time between studies. All studies were reviewed by our study team. The degree of hydronephrosis on RBUS was assessed using the Society for Fetal Urology grading system. VCUGs were assessed for the presence of vesicoureteral reflux, and the images were evaluated for the presence of bladder trabeculations (graded mild, moderate, and severe), the appearance of the bladder neck during leak/void (open, closed, open with a closed sphincter), and the shape of the bladder (round, elongated, conical/“Christmas tree”). DLPP or EFP were assessed on the UDS. DLPP and EFP were assessed as continuous variables but were also risk stratified into 3 groups (<25 cm H2O, 25-40 cm H2O, and >40 cm H2O) for analysis.

A total of 129 patients were identified who met study inclusion criteria. Median age at UDS was 9.6 years (IQR 3.2-14 years). Median time between UDS and RBUS was 2.0 months (IQR 0.9-3.5 months), and median time between UDS and VCUG was 2.4 months (IQR 1.1-3.8 months). When analyzing RBUS findings with DLPP/EFP as a continuous variable, worsening degrees of hydronephrosis appeared to correlate with higher DLPP and EFP (Table 1). This correlation was, however, lost when DLPP and EFP were analyzed categorically into the stratified risk categories (Table 2). When DLPP/EFP were analyzed both continuously and categorically, nonround bladder shape and severity of trabeculations had a high level of correlation with higher DLPP/EFP (P < .0001). The presence of vesicoureteral reflux notably did not correlate with higher DLPP and EFP in any of our analyses (Tables 1 and 2).

This study indicates that hydronephrosis on RBUS, bladder shape on VCUG, and severity of bladder trabeculations on VCUG correlate with high-risk bladder characteristics on UDS. Interestingly, our analysis suggests that these VCUG findings may correlate more strongly with higher DLPP/EFP than hydronephrosis on RBUS. As these correlations were noted retrospectively, prospective studies are needed to better understand the predictive value of RBUS and VCUG findings in the identification of high-risk features in neurogenic bladder.