A new and automated method for objective analysis of detrusor rhythm during the filling phase

Introduction

There is growing acceptance that the detrusor muscle is not silent during the filling phase of the micturition cycle but displays low-amplitude phasic contractions that have been associated with urinary urgency. Unfortunately, there is currently no standardized methodology to quantify detrusor rhythm during the filling phase. Therefore, the purpose of this study was to develop an automated computer algorithm to analyze rat detrusor rhythm in a quick, accurate, and reproducible manner.

Materials and methods

Strips of detrusor smooth muscle from rats (n = 17) were placed on force transducers and subjected to escalating doses of PGE₂ to generate contractile rhythm tracings. An automated computer algorithm was developed to analyze contractile frequency, amplitude, and tone on the generated rhythm tracings. Results of the automated computerized analysis were compared to human (n = 3) interpretations. Human interpreters manually counted contractions and then recounted the same data two weeks later. Intra-observer, inter-observer, and human-to-computer comparisons were performed.

Results

The computer algorithm quantified concentration-dependent changes in contractile frequency, amplitude, and tone after administration of PGE₂ (10^?9–10^?6M). Concentration–response curves were similar for all contractile components with increases in frequency identified mainly at physiologic concentrations of PGE₂ and increases in amplitude at supra-physiologic concentrations. The computer algorithm consistently over-counted the human interpreters, but with less variability. Differences in inter-observer consistency were statistically significant.

Conclusions

Our computerized algorithm accurately and consistently identified changes in detrusor muscle contractile frequency, amplitude, and tone with varying doses of PGE₂. Frequency counts were consistently higher than those obtained by human interpreters but without variability or bias. Refinements of this method may allow for more standardized approach in the study of pharmacologic agents on filling phase rhythmic activity.