Non-invasive assessment of urinary bladder compliance using ultrasound: first validation study based on clinical urodynamic study

Background This study aims to validate a recently introduced non-invasive method, ultrasound bladder vibrometry (UBV), for the assessment of detrusor compliance in patients with neurogenic bladders. Methods The study was carried out on 79 adult patients with neurogenic bladders (60 male and 19 female). The UBV test was performed on each patient to measure the Lamb wave group velocity (cg ) in the anterior bladder wall at every 50mL volume increment throughout the filling phase. Bladder compliance was assessed based on the trend of Lamb wave group velocity squared (cg2 ) versus volume. A compliance index was defined to differentiate between the compliant and non-compliant bladders. Results of the UBV compliance assessment were validated using the readings of the corresponding urodynamic studies as the clinical gold standard. Results The Patients' bladders were divided into non-compliant and compliant groups by an experienced urologist using the information in the urodynamic study (UDS) recordings. The compliance index defined on the basis of cg2 showed a significant difference (P<0.008) between the compliant and non-compliant groups. The areas under the receiver operating characteristic curve were 0.813, with 95% CI ranging from 0.709 to 0.892. Under the optimal criterion, the bladder was considered as non-compliant if the compliance index was less than 100 mL∙s2/m2, resulting in a sensitivity and specificity of 86.4% and 71.9%, respectively. Conclusions The results of this study demonstrate that UBV can be used as a non-invasive method for the determination of bladder compliance; thus, it can potentially serve as an alternative method to UDS for the appropriate patient groups.