Overactive bladder syndrome (OAB) is defined by the International Continence Society (ICS) and the International Urogynecological Association (IUGA) as urgency, with or without urgency urinary incontinence, usually accompanied by daytime frequency and nocturia, in the absence of urinary tract infection or other obvious pathology. Destrusor overactivity (DO) in the urodynamic observation characterized by the occurrence of involuntary detrusor contractions during filling cystometry and can be demonstrated en 44-54% of women with symptoms of OAB (1), and 47% of asymptomatic women can present DO (3).  

Few studies have attempted to associate urodynamic variables with clinical symptoms have failed to demonstrate significant relationships. The lack of a validated measures of DO severity tool limits the clinical value of urodynamics in the management of patients with OAB. Various tests can help detect detrusor instability. Nevertheless, it is still not possible to derive a reliable parameter from conventional urodynamics to quantify the grade of detrusor overactivity.

The aim of this study was to evaluate the correlation between the Indevus Urgency Severity Scale (IUSS) and urodynamic findings in patients with detrusor overactivity (DO) in a urodynamic study.

The design was a retrospective observational study. It was made in a Urogynecology referal clinic. All patients were assessed using the IUSS and a questionnaire on urological symptoms and were stratified in 4 groups according to de IUSS (none, mild, moderate, severe). A complete urodynamic study was performed, according to the ICS recommendations; the presence of DO was recorded. The clinical and urodynamic findings were analyzed. Fisher´s exact test for categorical variables and analysis of variance (ANOVA)for continuous variables. Statistical assessments were considered significant when P<0.05. Statistical analyses were performed using SPSS 24.00.

We analyzed the results of 827 urodynamic studies. 58 patients presented DO. The results are shown on table 1.

Fist sensation, first desire, strong desire and maximum cystometric capacity were the variables with the most statistically significant associations in this study, comparing patients with and without OAB symptoms. Comparing other urodynamic variables related to the detrusor overactivity (amplitude of the first IDC, the amplitude of the highest IDC and the threshold volume for the first IDC) we found no significant association.

Neither medical history nor clinical diagnosis based on urodynamic investigations have proved to be a 100%reliable to determine whether patients suffer from bladder overactivity, nevertheless, these are the best options available (2). This study identified a number of urodynamic variables with statistically significant association with the severity of OAB symptoms.

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van Waalwijk van Doom ES, Ambergen AW, Janknegt RA. Detrusor activity index: quantification of detrusor overactivity by ambulatory monitoring. The Journal of urology. 1997 Feb 157(2):596-9
Bradshaw HD, Radley SC, Rosario DJ, Chapple CR. Towards a better understanding of involuntary detrusor activity. BJU International. 2005 Apr;95(6):799–803