Is low bladder compliance predictive of detrusor overactivity?

Bladder compliance (BC) expresses the relationship between bladder volume and bladder pressure and is generally regarded as a measure of bladder stiffness or distensibility. Many types of voiding dysfunction have been associated with low BC such as detrusor overactivity (DO). It has previously been reported that the presence of DO is an independent predictor of low BC. The aim of this study was to assess the predictive value of low BC for the diagnosis of idiopathic DO using ambulatory urodynamics as the gold standard investigation for comparison.

All patients with LUTS attending a single center for both conventional and ambulatory urodynamics over a 5-year period were reviewed. The predictive value of various set levels of BC was compared using a receiver-operator characteristics (ROC) curve in an attempt to find the optimal threshold of BC for the diagnosis of DO.

162 patients were identified and following exclusions 143 (88%) data sets were suitable for analysis. The mean (s.d.) BC in the 99 patients with DO was 92 (80) ml/cm H(2)O compared to 112 (91) ml/cm H(2)O in those who did not show DO on ambulatory urodynamics. This difference was not statistically significant according to a non-parametric Mann-Whitney test (P = 0.22). Furthermore no set threshold of BC was able to provide sufficient accuracy for the diagnosis of DO. The area under the curve was less than 0.5 (0.47) indicating a level of accuracy less than "chance".

Low bladder compliance is not predictive of DO in our series. It is imperative to note that our results are obtained from a cohort comprising predominantly female patients without BOO and is therefore different to previous reports concentrating on male patients with BOO.