Both the American Urological Association (AUA) and the Canadian Urological Association (CUA) endorse a risk-stratification and surveillance protocol for neurogenic lower urinary tract dysfunction (NLUTD), categorizing patients into low-, moderate-, and high-risk groups with tailored monitoring. This study evaluated whether intravesical OnabotulinumtoxinA (BTX-A) impacts upper urinary tract (UUT) parameters differently in moderate- vs. high-risk patients.

We conducted a retrospective analysis (January 2017–January 2023) of all adult NLUTD patients who received BTX-A injections. Inclusion criteria required ≥2 years of follow-up with serum creatinine, GFR, and renal ultrasound assessments. Pediatric and low-risk patients were excluded.

The primary outcome was to compare the effect of BTX-A on serum creatinine, GFR, hydronephrosis (HN), and vesicoureteral reflux (VUR) between the two groups.
Secondary outcomes were to evaluate the impact of BTX-A injection on UTI incidence, BTX-A dose adjustments, self-catheterization frequency and to determine whether correlations exist between BTX-A injection results and urodynamic parameters (bladder capacity, neurogenic detrusor overactivity [NDO], compliance, DLPP), or pharmacotherapy regimens.
Statistical analyses included paired t-tests, chi-square, and multivariate regression.

We found 74 patients (mean age 36.8 ± 12.2 years, 47.3% male, 52.7% female), with etiologies including spinal cord injury (n= 32, 43.2%), multiple sclerosis (n= 14, 18.9%), meningomyelocele (n= 4, 5.4%), disc disease (n=22, 29.7%), and others (n= 2, 2.8%).

BTX-A significantly improved serum creatinine (p= 0.008), and hydronephrosis (p< 0.001). GFR increased (+21.5 vs. +10.2 mL/min, p= 0.016). High-risk patients showed more significant improvement in serum creatinine and GFR than moderate-risk ones (creatinine improved: 75.9% vs 35.6%, p< 0.001), (GFR increased: +21.5 mL/min vs. +10.2 mL/min). Hydronephrosis improved post-BTX-A more in high-risk compared to moderate-risk patients (68% vs 58%, p= 0.04). Urinary tract infections were reduced more after BTX-A injection in high-risk compared to moderate-risk patients (76% vs. 40%, p< 0.05).

A statistically significant association was observed between female gender and greater improvement in hydronephrosis following BTX-A treatment (p= 0.03). Patients with spinal cord injury demonstrated the most substantial reduction in serum creatinine levels post-BTX-A when compared to other diagnostic groups (p= 0.02). Those receiving combination therapy showed a trend toward more frequent hydronephrosis improvement than patients on monotherapy (65% versus 50%, p= 0.08). Urodynamic assessment revealed that normal bladder capacity served as a predictor for creatinine improvement (OR= 2.4, p= 0.01), while the absence of neurogenic detrusor overactivity (NDO) was correlated with enhanced GFR outcomes (OR= 1.9, p= 0.03). When analyzing dose adjustments and excluding patients who started with 300 IU, 22% of moderate-risk patients versus 35% of high-risk patients required dose escalation in subsequent injections (p= 0.09). Furthermore, patients exhibiting improved GFR after BTX-A treatment demonstrated a significant tendency to reduce their daily self-catheterization frequency (p= 0.01).

OnabotulinumtoxinA (BTX-A) demonstrated significant improvement in upper urinary tract (UUT) parameters and reduction in urinary tract infection (UTI) rates, with these therapeutic effects being particularly pronounced in high-risk neurogenic bladder patients. Urodynamic characteristics, including normal bladder capacity and absence of neurogenic detrusor overactivity (NDO), could be potential predictive factors for positive BTX-A response. These findings support the clinical utility of the current risk stratification and surveillance protocol, particularly for detecting patients at elevated risk of UUT deterioration. The interpretation of these results should consider the study's limitations, including its retrospective nature and relatively small cohort size.

BTX-A effectively stabilizes UUT function in NLUTD patients, with effects being particularly evident in high-risk patients. Pre-BTX-A urodynamic parameters may predict therapeutic response to BTX-A, while UUT imaging surveillance protocol possibly would optimize outcomes. These findings substantiate the clinical relevance of the existing risk stratification system of neurogenic bladder. However, prospective studies are necessary to validate these findings.

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