Surrogate imaging markers of Urodynamic proven bladder dysfunction in posterior urethral valves: A comprehensive evaluation

Abstract

Introduction: Although urodynamic evaluation forms the cornerstone of diagnosis and management of bladder dysfunction in posterior urethral valves (PUV), yet it could be helpful to learn if there are any non-invasive surrogate imaging markers for the same.

Aim: To study the diagnostic accuracy of various imaging surrogate markers of urodynamic proven bladder dysfunction in PUV.

Method: This cross-sectional study over two years included 38 children of endoscopically proven PUV. Based on bladder function on Urodynamics the patients were divided into 2 groups: Group 1: PUV with normal bladder function (n: 17, 44.7%); Group 2: PUV with impaired bladder function (n: 21, 55.3%). Voiding dysfunction, incidence of recurrent urinary tract infection (UTI), polyuria, grade of hydronephrosis, retrovesical ureteric diameter (mm) and detrusor wall thickness (DWT mm) was compared in the two groups. MCU at initial presentation and post definitive treatment was studied and a bladder hostility score (BHS) was assigned to each patient and compared in the two groups. Correlation between impaired bladder function and clinical and radiological variables was performed by using Spearman Rank correlation and data receiver operating curves (ROC) were plotted to identify the critical values predicting the probability of bladder dysfunction in PUV.

Results: Mean age at evaluation was 6.1 ± 4.2 years with a mean follow-up of 5 ± 3.9 years (median: 3.5 years). Voiding dysfunction, persistent or worsening grade III and IV hydroureteronephrosis, retrovesical ureter diameter ≥13.1 mm (diagnostic accuracy: 68.4%, AUC: 0.738), DWT on full bladder ≥1.85 mm (diagnostic accuracy: 81.6%, AUC: 0.846) and pretreatment BHS ≥5.5 (diagnostic accuracy: 71.4%, AUC: 0.763) were the clinical and imaging predictors of impaired bladder function. Comparative analysis of the two groups is as shown in table.

Conclusion: Clinical and imaging parameters are unable to convincingly identify the type of bladder dysfunction which is often required to manage PUV patients appropriately. Increased detrusor wall thickness suggests underlying bladder dysfunction and while those with small capacity hypertonic bladders have higher mean detrusor wall thickness than those with myogenic failure, the difference was not statistically significant (p: 0.41). Attempts to predict underlying bladder dysfunction by MCU imaging may be erroneous in nearly one-third of the patients. Thus, these imaging parameters are complementary and sequential to urodynamic, which certainly continues to be the gold standard investigation to assess bladder dysfunction in PUV.

Keywords: Bladder dysfunction; Imaging findings; Posterior urethral valves; Surrogate markers; Urodynamics.