Detrusor Overactivity with Impaired Contractility or the Co-existing Overactive-Underactive Bladder Syndrome (COUB): A Management Conundrum

Although the coexistence of detrusor overactivity and impaired contractility was described first in the late 1980s, the interest in the presence of both of these two apparently opposite conditions in the same individual has increased in the last few years. The most commonly used contemporary terminology to define a condition of impaired detrusor contractility is “detrusor underactivity.” Thus, talking about detrusor overactivity and underactivity in the same individual may look like a paradox if one would not understand that “overactivity” is seen in the filling phase, while “underactivity” may be present in the voiding phase of the micturition cycle. The same detrusor can have “inappropriate” (involuntary, overactive) contractions, while being unable to produce an effective contraction during voiding. These two urodynamic observations may provoke a mixed and variable symptomatology in the filling and voiding phases that can be very bothersome for the patient. Some authors have proposed that an abnormally activated detrusor during the filling phase, without a complete rest, may waste the energy required for the next voiding phase, which is then impaired due to muscle asthenia and exhaustion. Other pathophysiological explanations may be bladder wall ischemia, bladder denervation or bladder outlet obstruction: these conditions may be able to produce both detrusor overactivity and underactivity. The presence of a voiding dysfunction may prevent the use of specific drugs (e.g., antimuscarinics) for the risk of increasing the post-void residual urine or, possibly, causing acute urinary retention. A beta-3 agonist may be a good option to treat detrusor overactivity without affecting bladder voiding. Neuromodulation techniques such as sacral nerve or tibial nerve electrical stimulation may be able to impact on both detrusor dysfunctions, thus representing an attractive therapeutic option in patients with detrusor over/underactivity. In general, it is always advisable to try to determine the possible underlying pathophysiology in every single patient, to identify the best therapeutic strategy. For this purpose, an invasive urodynamic evaluation may be generally advisable in patients with detrusor over/underactivity, especially when conservative treatments and oral agents have not been successful.

What is the proportion of patients with voiding difficulty in your practice that have this condition?

It depends on which category of patients we consider. Among patients with neurogenic impairment (particularly among multiple sclerosis patients), the prevalence is quite high (probably up to 50% of patients with voiding difficulties). Among non-neurogenic patients, the figures are lower.

What is the treatment protocol that in your opinion works best for these patients?

Neuromodulation techniques may work better in these patients. Almost all the other therapeutic options for OAB may impact on the voiding phase.

Do you use SNM or tibial nerve stimulation in your practice for this condition? If yes, what are the results?

I regularly use tibial nerve stimulation and I think it is a good option for patients with detrusor under- and over-activity, able to positively impact on both conditions.