Proposal for a Urodynamic Redefinition of Detrusor Underactivity

PurposeWe sought a sufficiently comprehensive urodynamic definition of idiopathic detrusor underactivity in men with nonneurological conditions and no obstruction who had mainly voiding lower urinary tract symptoms.Materials and MethodsIn 75 such patients and 40 age matched controls we retrospectively analyzed intrinsic detrusor contraction strength and contraction speed by estimating isovolumetric detrusor pressure and maximum possible detrusor contraction velocity. Bladder emptying efficiency was also determined. Nonparametric statistics were done as data analysis.ResultsDetrusor underactivity, defined as lower levels of maximum possible detrusor contraction velocity and/or isovolumetric detrusor pressure than the 25th percentiles of such parameters in controls, was found in all 75 patients. Patients could be divided into group 1—22 with low maximum possible detrusor contraction velocity, low isovolumetric detrusor pressure and bladder emptying efficiency less than 67%, group 2—25 with low maximum possible detrusor contraction velocity, low isovolumetric detrusor pressure and bladder emptying efficiency 67% or greater, and group 3—28 with low maximum possible detrusor contraction velocity, normal isovolumetric detrusor pressure and bladder emptying efficiency 67% or greater. For insignificantly different urethral resistance levels there were significant decreases in maximum possible detrusor contraction velocity in group 3 vs those in controls, and in maximum possible detrusor contraction velocity and isovolumetric detrusor pressure in groups 2 and 1 vs those in group 3.ConclusionsIn our patients with detrusor underactivity intrinsic detrusor speed was more compromised than intrinsic strength. The definition of idiopathic detrusor underactivity of a slower and/or weaker bladder with or without poorly sustained micturition contractions proved more effective than a definition of decreased detrusor contraction strength and/or poorly sustained micturition contractions. The decreasing trend in detrusor contractility from group 3 to groups 2 and 1 suggests that our classification of idiopathic detrusor underactivity may reflect the evolution of this condition from an initial stage to obviously impaired voiding function.