Ultrasound Shear Wave Elastography: A Novel Method to Evaluate Bladder Pressure

Abstract

Children with bladder dysfunction resulting in increased storage pressure are at risk for renal deterioration. The current gold standard for evaluation of bladder pressure is urodynamics, an invasive test requiring catheterization. We evaluated ultrasound shear wave elastography as a novel means of assessing bladder biomechanical properties associated with increased bladder pressure. Concurrent shear wave elastography and urodynamics were performed. Ultrasound shear wave elastography images were obtained of the anterior and posterior wall when empty and at 25%, 50%, 75% and 100% expected bladder capacity, and end fill volume. Regions of interest were confirmed by a pediatric radiologist. Bladder cohorts were defined as compliant (capacity detrusor pressure less than 25 cm H2O) and noncompliant (25 cm H2O or greater). Pearson correlation coefficients and a mixed effects model evaluated the relationship between shear wave speed and detrusor pressure, compliance and normalized compliance. An unpaired t-test was used for between cohort analyses. In all 23 subjects mean shear wave speed of the anterior and posterior bladder walls significantly correlated with detrusor pressure throughout filling. When comparing compliant and noncompliant bladders, mean shear wave speed and detrusor shear wave speed of the anterior wall significantly increased with filling of noncompliant bladders. Shear wave speed remained at baseline levels in compliant bladders. Mean shear wave speed of the anterior wall was significantly correlated with compliance and normalized compliance. Ultrasound shear wave elastography bladder measurements correlate well with bladder storage pressure, and shear wave speed measurements differ between compliant and noncompliant bladders. This is the first known study to demonstrate that shear wave elastography is promising as a bedside modality for the assessment of bladder dysfunction in children.