Different evolution of voiding function in underactive bladders with and without detrusor overactivity

We assessed bladder voiding function in patients with idiopathic detrusor underactivity with and without detrusor overactivity for a different evolution in time.

We retrospectively analyzed clinical and urodynamic findings in 36 consecutive middle-aged men with idiopathic detrusor underactivity who were referred during 1989 to 2003 for voiding and storage lower urinary tract symptoms. After initial testing at time 1 urodynamics were repeated due to worse lower urinary tract symptoms severity at a median of 45 months (time 2). A total of 17 patients with voiding urgency showed urodynamic detrusor overactivity at times 1 and 2 (group 1) and 19 with no urgency (group 2) never had detrusor overactivity. As controls (group 3) we used 30 age matched, urodynamically normal men. Nonparametric statistics were used for data analysis.

Compared with controls at time 1 groups 1 and 2 had lower bladder emptying efficiency and bladder contractility (contraction strength, velocity and energy reserve) with relatively higher contraction velocity and energy reserve in group 1 than in group 2. Compared with time 1 at time 2 the 2 detrusor underactivity groups showed an increased International Prostate Symptom Score (more increased in group 1), and decreased bladder contractility and emptying efficiency (less decreased in group 1).

A likely explanation for our findings is that by causing relatively more rapid (less slow) detrusor contractions detrusor overactivity partly decreased the time needed and, thus, the total energy expended by underactive bladders for mounting micturition contractions. This compensatory efficiency would account for the relatively better evolution of bladder voiding function with time.