Most Men with Detrusor Underactivity Regain Spontaneous Voiding After Outlet Procedure

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Underactive bladder, also called bladder detrusor underactivity (DU), is often not diagnosed until late in its course, when the dysfunction is typically considered irreversible. Too often, the lower urinary tract symptoms are assumed to be due to bladder outlet obstruction (BOO) and DU is suspected only after surgical treatment fails.

Urologist Elise J.B. De, MD, of the Department of Urology at Massachusetts General Hospital, Amy D. Dobberfuhl, MD, MS, of Stanford University School of Medicine, and colleagues are working to identify therapies that will improve bladder contractile strength. They recently reported in Neurourology Urodynamics that a surprising number of men with DU benefit from de-obstruction surgery.

Study Details

The researchers studied 122 men who had a de-obstructive outlet procedure between October 2005 and August 2014, underwent preoperative urodynamic pressure-flow evaluation of the bladder outlet and had tracings and complete follow-up data available for review.

DU was defined as a bladder contractility index (BCI) of <100 (calculated as detrusor pressure at maximum flow + 5 × maximum flow rate). DU was identified in 66 patients (54%), and only 45 of them (68%) could void spontaneously before surgery, compared with 82% of the 56 men who had BCI ≥100.

All men with DU who underwent an outlet procedure had clinically suspected obstruction (e.g., trabeculation, bi- or tri-lobar hypertrophy or urodynamic confirmation), and there was no suspicion of an overriding neurologic cause.

Primary Outcome

The primary outcome was the ability to spontaneously void after surgery without the need for intermittent catheterization or an indwelling catheter. After average follow-up of 6.4 months, 79% of the patients with DU and 96% of those with BCI ≥100 were able to void spontaneously.

On logistic regression analysis, the following characteristics were significantly associated with greater odds of postoperative spontaneous voiding:

• Preoperative spontaneous voiding (odds ratio [OR], 9.46)
• BOO index > 40 (OR, 5.60)
• Increased maximum flow rate (OR, 1.18)
• Increased detrusor pressure at maximum flow (OR, 1.03)

Characteristics associated with reduced odds of spontaneous voiding postoperatively were:

• DU (OR, 0.14)
• Increased preoperative postvoid residual (OR, 0.997)

A Closer Look at Patients With DU

Twenty-one of the 66 patients with DU were unable to void before surgery. Postoperatively, 12 patients in that subgroup (57%) were able to void spontaneously following surgery and nine were not. There were no statistically significant differences between those groups in any preoperative characteristic.

Guidance for Patient Counseling

Whether men with lower urinary tract symptoms should be counseled to pursue a de-obstructive outlet procedure depends on the presence of preoperative spontaneous voiding, obstructive parameters, flow and bladder contractility. During patient counseling, surgeons should provide guidance on whether it is reasonable to expect spontaneous voiding after surgery.

The study findings support the use of pressure-flow urodynamic studies to evaluate men who are considered likely to have DU. Even if the bladder outlet does not meet the conventional threshold for obstruction (BOO index >40), it may be reasonable to offer a de-obstructive outlet procedure to men who demonstrate poor bladder contractility.

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