Detrusor contractility in women: Influence of ageing and clinical conditions

We assume that the voiding process in women is governed by the detrusor contractility and a "urethral resistance". The value of these 2 parameters, respectively named k and U in the VBN (Valentini-Besson-Nelson) mathematical model of micturition is deduced from the VBN analysis of pressure-flow recordings (PFs). Our objectives were to search for a correlation between these 2 parameters and clinically relevant variables such as chief complaint, urodynamic diagnosis (UD), and age by decades.

PFs from 125 non-neurogenic women (mean age 58.0±17.2years [range 20-90years]) were retrospectively analyzed using the VBN model. VBN criteria for inclusion were maximum flow rate>2mL/s, voided volume>100mL, and non-interrupted flow. Evaluated parameters were k (without unit) and U (unit: cm H2O). Standard values were k=1.0 and U=0.

VBN parameter ranges were k [0.14-1.55] and U [0.0-73.0cm H2O]. There was a significant correlation between k and U for the whole population (P<0.0001) with k=(.259+0.015*U) (R(2)=0.723) and each chief complaint. For UD, significant difference comparing k and U in phasic detrusor overactivity with intrinsic sphincter deficiency and urodynamic stress incontinence was noted. In sub-groups defined according to decades of age, the values of k and U remained similar in sub-groups for those who are less than 50years old and decreased regularly with ageing.

The detrusor contractility can be easily evaluated in women; lower than in men, its range is less spread out but also adjusted to compensate a "urethral resistance". Phasic detrusor overactivity and post-menopausal age significantly affect detrusor force value.

3.