The symptoms of detrusor overactivity with impaired contractility (DOIC) are not a little encountered in clinical practice, however, the specific definition and diagnostic criteria for DOIC have not been standardized yet, although it has been over 30 years since it was first announced. Moreover, its prevalence and clinical characteristics have not yet been clearly identified in the community-dwelling elderly with non-neurogenic lower urinary tract symptoms and the debate on the underlying etiology and pathophysiology continues over whether DOIC is developed from a single pathophysiological mechanism or merely reflects the coexistence of independent detrusor overactivity (DO) and detrusor underactivity (DU). We aimed to identify the prevalence of DOIC in the community-dwelling elderly with non-neurogenic lower urinary tract symptoms and compare urodynamic characteristics of DOIC with those of DO only and DU only in order to explore whether it is from a single or two independent bladder dysfunctions.

Based on a 10-year urodynamic database of the SEOUL Study Group, elderly patients aged 65 or older who met inclusion criteria were selected. Fig. 1 depicts the cohort selection process for male and female patients from urodynamic database registry. After eliminating data of patients with the exclusion criteria, 2,571 men and 688 women were enrolled in the initial analyses for the prevalence. Finally, data of 1,933 men and 276 women who were proven to have urodynamic DO and/or DU were entered into the analyses regarding the urodynamic association between the patients with DOIC, DO only, and DU only. DO was considered positive when spontaneous or provoked involuntary detrusor contraction was observed in the filling cystometry regardless of urine leakage and size of amplitude, as indicated by the ICS. With regard to the definition of DU, a formulated bladder contractility index was used for men, and the combination of PdetQmax < 30 cmH2O and PFS Qmax < 10 mL/s for women. DOIC was defined when DO was observed in a filling cystometry and each criteria of DU was proven for men and women in a pressure-flow study. Bladder sensation, capacity, and compliance were designated as evaluation elements for storage function, and free Qmax and post void residual volume, PdetQmax, and bladder voiding efficiency for voiding function.

Of 2,571 men and 688 women, the prevalence rate of DOIC was 18.8% and 5.5% in male and female population, and increased significantly with age. In men, patients with DOIC showed no differences in storage parameters and significantly lower free Qmax and PdetQmax among voiding parameters, compared to those with DO only. Compared to men with DU only, those with DOIC had worse parameters in the majority of storage and voiding functions. In women, most of the storage and voiding functions were worse in patients with DOIC than in those with DO only. On the other hand, women with DU showed lower PdetQmax and worse voiding functions than those with DOIC, although some parameters did not reach statistical significance.

We think this approach in which the association of each condition is explored using urodynamic parameters may help investigate the possible pathophysiological mechanism of DOIC and lay a foundation for further research on DOIC. According to the present findings, in men, it was identified that urodynamic features of DOIC were similar with those of DO only with regard to the storage function, but
were worse than those of DO only regarding the voiding function. Compared to the urodynamic features of DU only, those of DOIC were more aggravated in the storage and voiding functions. Therefore, it seems that DOIC, DO only, and DU only have no sequential relationship when all these urodynamic conditions are arranged in the degree of deterioration of both storage and voiding function index, when compared between groups. Instead, DOIC is likely to reflect the complex condition of two independent bladder dysfunctions such as DO and DU in men. Unlike in male patients, urodynamic features in female patients with DOIC were worse than those in patients with DO only in both storage and voiding functions, and urodynamic features of DU only deteriorated more than those of DOIC regarding the voiding function. Thus, with regard to the voiding function, there was the sequential relationship in the degree of deterioration of urodynamic parameters, in which urodynamic parameters of DOIC deteriorated more than those of DO only, and those of DU only was more aggravated than those of DOIC. It seems that DOIC is likely to be an intermediate step during the process of progression from DO to DU in women. If all these findings are put together, it may be cautiously suggested that, urodynamically, the association of DOIC with DO only and DU only is different between genders.

Urodynamically, the association of DOIC with DO and DU may be different between both genders. In men, it seems that DOIC is developed from a coincidental combination of two independent DO and DU. In contrast, DOIC is likely to be an intermediate step during the process of progression from DO to DU in women.