A detrusor after-contraction (DAC) is a poorly defined urodynamic observation, that occurs during the voiding phase of the test. The prevalence of this phenomenon vary widely in the literature, but one of the largest cohorts of symptomatic women reported it at 13.9% on conventional urodynamics (1). This has been shown to be as high as 37% on ambulatory urodynamics (2).The clinical significance of this observation remains disputed. Some hypothesise that it is merely an artefact of no clinical value, while other papers have shown significant correlations between detrusor overactivity (DO) and the presence of a DAC (2). It has also been demonstrated that there is no link between detrusor underactivity (DU) and DAC (3). 

The aim of this study is to determine the prevalence of DAC in our urodynamics cohort, and their association with DO, bladder outlet obstruction (BOO), urodynamic stress incontinence (USI) and normal urodynamic studies.

This was a retrospective study, using data obtained from patients who underwent urodynamic testing at a single centre. This included conventional and ambulatory urodynamic studies. Data obtained included age, sex, urinary symptoms, urodynamic results and diagnostic conclusions. Data was screened, and records that were incomplete were excluded from analysis. 

Descriptive statistics of patient cohort have been summarised. Microsoft Excel was used to calculate odds ratios for each urodynamic diagnosis in relation to DAC, with 95% confidence intervals..

Of the original 7958 data records, 4303 were included in analysis. 1614  (37.5%) were men, and 2689 (62.5%) were women. The age range was 16-96 years old, with a mean age of 56 years.

DAC was present in 13% of all patients who underwent urodynamics. It was more prevalent in women than men, with 15.3% of women exhibiting this phenomenon compared to 9.2% of men. Of the 558 studies which showed DAC, 73% were in women.
11.8% of ambulatory urodynamic studies showed DAC, compared to 13% for conventional urodynamics. 

Table 1 shows odds ratios calculated for DAC in relation to DO, BOO or USI. DAC was positively associated with detrusor overactivity (OR = 2.18), while USI was negatively associated with DAC (OR=0.42). There was no statistical significance for bladder outlet obstruction (OR = 0.93) or those with normal studies (OR = 0.93) in relation to DAC.

We have shown an overall prevalence of 13% for DAC, which is similar to a previous study with a similar sized cohort (1). 11.8% of ambulatory studies showing DAC. This is significantly lower than documented in a previous study (2). The variation in prevalence on ambulatory studies is likely due to a difference in the number of filling and voiding cycles performed.

This study has shown that there is a positive association between DAC and DO. For patients with after contractions, they were more than twice as likely to have a diagnosis of DO than those without DAC. This is similar to what has been previously reported (2), and therefore we reject the hypothesis that DAC is merely artefactual.  There was no association between normal studies, BOO and DAC, and a negative association with USI. This further supports the idea that this may be pathological rather than artefact. The link between DAC and DO also poses the following question - in the absence of phasic waves during the filling phase, can we use DAC alone to diagnose DO? Further studies are required.

For symptomatic patients, the prevalence of DAC is 13%. There is a significant positive association between this phenomenon and detrusor overactivity, which is not seen in other urodynamic diagnoses. This may be of diagnostic value for patients who do not exhibit DO during the filling phase of conventional urodynamics, however more research is necessary.

Rodrigues, P., Hering, F. and Campagnari, J.C. (2014) “Urodynamic after-contraction waves: A large observational study in an adult female population and correlation with bladder and ureter emptying functions in women,” Urologia Internationalis, 93(4), pp. 431–436. Available at: https://doi.org/10.1159/000360139.
Veeratterapillay, R. et al. (2015) “Detrusor after-contraction on ambulatory urodynamics in Symptomatic women,” International Journal of Urology, 22(11), pp. 1058–1062. Available at: https://doi.org/10.1111/iju.12887.
Gammie, A. et al. (2018) “Signs and symptoms that distinguish detrusor underactivity from mixed detrusor underactivity and bladder outlet obstruction in male patients,” Neurourology and Urodynamics, 37(4), pp. 1501–1505. Available at: https://doi.org/10.1002/nau.23492.