Posterior urethral morphology on initial voiding cystourethrogram correlates to early renal outcomes in infants with posterior urethral valves
Charlotte Wu, MD1, Emily S. Blum, MD2, Edwin A. Smith, MD2.
1Johns Hopkins University School of Medicine, Baltimore, MD, USA, 2Emory University School of Medicine, Atlanta, GA, USA.
BACKGROUND: Posterior urethral valves (PUV) are a leading cause of chronic renal failure in childhood. Bladder and posterior urethral deformity in infants with PUV are highly variable on initial voiding cystourethrogram (VCUG). Some types of deformity may be more important than others in determining the severity of the condition. Herein, we sought to determine whether these morphological features correlate to initial renal outcomes as measured by the creatinine nadir in the first year after ablation. Identification of specific VCUG features may allow for an additional early, simple screening assessment in these children. METHODS: Children with PUV treated by primary valve ablation before 12 months old and followed > 1 year were identified. Initial diagnostic VCUG was evaluated for the bladder height to width ratio (HW-B), posterior urethral height to width ratio (HW-PU), and posterior-anterior urethral ratio (PA-UR). A trabeculation grading was assigned by three pediatric urologists, and reflux was noted as unilateral, bilateral, or absent. Univariable analyses with chi-square and t-test were used to compare bladder and posterior urethral morphology factors among those who obtained a creatinine nadir <0.8 or ≥ 0.8 in the first year after ablation. Linear regression was performed to assess the degree of correlation between the morphology values and creatinine nadir. RESULTS: A total of 120 boys were ablated at mean age of 40.5 days (range 0-342) and followed for 5.9 years (SD 3.85). Among these, 21 (17.5%) had a creatinine nadir ≥ 0.8. Mean overall HW-B and mean PA-UR were not significantly different between those with creatinine nadir < 0.8 versus ≥ 0.8. Bladder trabeculation grading was not associated with creatinine nadir. For the entire cohort, only the difference in HW-PU was statistically significant between creatinine nadir groups with a much higher ratio among those with a nadir ≥ 0.8 (p< 0.001). Linear regression demonstrated a significant positive correlation between the HW-PU and creatinine nadir (R2= 0.097, p = 0.002). The presence of bilateral reflux is significantly associated with creatinine nadir ≥ 0.8 (p = 0.001). CONCLUSIONS: Some features on the initial VCUG are telling of the early renal outcomes that can be expected in infants with PUV. The presence of bilateral reflux or urethral deformity characterized by elongation of a distended posterior urethra are significantly associated with worse early renal outcomes. A higher HW-PU ratio on the initial VCUG is significantly correlated with a higher creatinine nadir. The degree of posterior urethral deformity, rather than bladder deformity, appears to be an indirect measure of the severity of obstruction in posterior urethral valves. This postulation warrants further investigation with targeted studies in the future.
Back to 2021 Abstracts