Determining the Ideal Index for Assessing Detrusor Contractility in Women: Insights from Urodynamic Diagnosis and Age

Aims: Detrusor contractility governs the voiding process. Its evaluation in women derived from an intubated flow is obtained from the contractility indices PIP1 and the VBN-derived parameter k. Both values of PIP1 and k are dependent of the urodynamic diagnosis (UD) and decrease with aging. Our goal was to find out if one of these indexes was more informative depending on UD and age.

Methods: Contractility was evaluated from pressure-flow studies of 354 non-neurologic women (age range 20-96 y) who were referred for investigation of various lower urinary tract dysfunctions and who fulfilled criteria for inclusion: non-interrupted flow, voided volume >100 mL and Qmax> 2mL/s.

UD were bladder outlet obstruction (BOO), detrusor hyperactivity with impaired contractility (DHIC), detrusor overactivity (DO), detrusor underactivity (DU). Some investigations were found “normal” (N) and other related to urethral dysfunction (intrinsic sphincter deficiency (ISD)) or voiding triggered by urethral relaxation (URA)). Data were interpreted across age-groups with 20 years interval, at least 3 patients with one UD in a given age-group interval.

Results: Among all the UD, only 2 did not have a sufficient number of patients to be reported: DHIC for 20-40y and URA for >80y. For each UD, variations of k and PIP1 demonstrated a decrease with age, which was more important for k in the age group >80y (compared with all age groups). Age–groups 20-40 and 41-60 gave comparable values of k and PIP1 for UD BOO, DO and DU. Analysis of percentage of contractility value variation showed a more important and significant decrease for k vs. PIP1 between age-groups 61-80 and >80 for all UD (p=.0028).

Conclusions: If both detrusor contractility indexes have values well related to urodynamic diagnosis which decrease with age, use of k is more informative than PIP1 in elderly women.