The diagnosis of underactive bladder (UAB) is typically made in the setting of urinary retention and elevated post void residual. UAB is often idiopathic or the sequela of bladder outlet obstruction, neurologic injury or poorly controlled diabetes. Symptoms are not specific and can include urinary hesitancy, urinary frequency, sensation of incomplete emptying and straining to void. The International Continence Society defines detrusor underactivity (DU) as a “Contraction of inadequate strength and/or duration resulting in prolonged emptying and/or failure to achieve complete emptying in the absence of urethral obstruction”. Despite intensive efforts to develop therapies aimed at improving bladder contractile strength and identifying this disorder earlier in life, bladder dysfunction is suggested to be irreversible at the time of diagnosis. We sought to identify clinical and urodynamic factors in men with suspected bladder outlet obstruction (BOO) with or without DU who underwent a de-obstruction procedure.

After obtaining institutional review board approval, we identified 614 men who underwent an outlet de-obstruction procedure at our institution over a 9-year period. From this group, we identified 131 men who underwent pre-operative urodynamic pressure flow evaluation of the bladder outlet. A two-reviewer case-by-case chart review was performed for: baseline patient characteristics, the presence of diabetes, history of urinary tract infection, alpha blocker use, 5-alpha reductase inhibitor use, pre-operative spontaneous voiding, AUA symptom and quality of life scores, pre-operative free uroflowmetry [maximum flow rate (Qmax), voided volume, post void residual (PVR)] and pre-operative pressure flow urodynamics [bladder capacity, the presence of detrusor overactivity, Qmax, detrusor pressure at maximum flow (Pdet@Qmax), PVR, and abdominal straining to void]. Our primary outcome of interest was the presence of the ability to spontaneous void after surgery without the need for intermittent catheterization or indwelling catheter. Data were analyzed in SAS (Cary, North Carolina, USA) for our primary outcome (spontaneous voiding after surgery) and the strata of bladder contractility index (BCI ≥ 100 versus BCI < 100) for our variables of interest using chi-square test, t-test, and logistic regression methods. Data are presented as mean ± standard deviation. A p-value <0.05 was defined as significant.

Of the 131 men who underwent urodynamics, 122 (mean age 68 ± 11 years) had pre-operative urodynamic tracing available for review. Baseline characteristics included diabetes in 22% (27/122), any instance of pre-operative UTI in 23% (28/122), the use of alpha blockers in 81% (99/122), the use of 5-alpha reductase inhibitors in 41% (50/122), a mean AUA symptom score of 18 ± 7.8 and quality of life score of 3.7 ± 1.6. Pre-operative free uroflowmetry demonstrated a mean Qmax 7.8 ± 5.7, voided volume 174 ± 145 and PVR 209 ± 221. On urodynamics, DU (BCI < 100) was identified in 54% (66/122) of men, with only 68% (45/66) voiding spontaneously prior to surgery, compared to 82% (46/56) of men with BCI ≥ 100. At a mean follow-up of 6.4 months, 79% (52/66) of men with DU were able to void spontaneously, compared to 96% (54/56) of men with BCI ≥ 100.

On logistic regression (Table 1) for the outcome post-operative spontaneous voiding, significant preoperative characteristics and urodynamic factors include: pre-operative spontaneous voiding (OR 9.460 95%CI 2.955 - 30.289), increased Qmax (OR 1.184, 95%CI 1.014 - 1.382), increased Pdet@Qmax (OR 1.032, 95%CI 1.012 - 1.052), DU with BCI < 100 (OR 0.138, 95%CI 0.030 - 0.635), and obstruction with BOOI > 40 (OR 5.595, 95%CI 1.685 - 18.575). Elevated pre-operative PVR alone was significantly, albeit weakly, associated with reduced odds of spontaneous void after a de-obstructive outlet procedure [free uroflowmetry PVR β = -0.003/mL (OR 0.997, 95%CI 0.995 - 0.999, p < 0.05); urodynamic PVR β = -0.002/mL (OR 0.998, 95% CI 0.996 - 1.000, p < 0.05)]. Factors which were not independently associated with spontaneous voiding after surgery include diabetes, pre-operative UTI, use of alpha blocker, use of 5-alpha reductase inhibitor, free uroflowmetry Qmax and voided volume, urodynamic bladder capacity, detrusor overactivity and the presence of abdominal straining.

When outcomes were stratified by bladder contractility for BCI ≥ 100 versus BCI < 100 (Table 2), the only baseline non-urodynamic characteristic that was significantly different between groups was the AUA quality of life score, which was worse in men with DU (mean 4.1 ± 1.5) versus men with BCI ≥ 100 (mean 3.4 ± 1.5). On urodynamics, all urodynamic parameters were significantly different between groups when stratified by bladder contractility. Weak bladders (BCI < 100) demonstrated: greater bladder capacity, PVR, and abdominal straining; and reduced detrusor overactivity, Qmax, Pdet@Qmax, and BOOI. In men with a weak bladder contraction (BCI < 100), only 32% (21/66) of men had a BOOI > 40 (p < 0.001). On post-operative follow-up, both AUA symptom score and quality of life score were significantly worse in men who had a weak bladder (BCI < 100) compared to those who did not. On follow-up, there was improvement in mean Qmax and PVR in both underactive (BCI < 100) and non-underactive bladders. There was a significantly greater Qmax noted at longest follow-up in men who had a strong bladder contraction prior to surgery [post-operative Qmax mean 16 ± 12 (BCI ≥ 100) versus 11 ± 6.5 (BCI < 100), p < 0.05].

DU portends a lower likelihood of spontaneous voiding and remains a difficult entity to predict without urodynamic evaluation. A surprisingly large number of men with DU were able to benefit from a bladder outlet de-obstruction procedure.

The decision for a man to pursue a de-obstructive outlet procedure should be individualized. Counseling should take into account the presence of pre-operative spontaneous voiding, obstructive parameters, flow, and bladder contractility; and should provide patient’s with guidance for the expectation of spontaneous voiding after surgery.

Osman NI, Chapple CR, Abrams P, et al. Detrusor underactivity and the underactive bladder: a new clinical entity? A review of current terminology, definitions, epidemiology, aetiology, and diagnosis. Eur Urol. 2014;65(2):389-398. doi:10.1016/j.eururo.2013.10.015
Chapple CR, Osman NI. Crystallizing the Definition of Underactive Bladder Syndrome, a Common but Under-recognized Clinical Entity. Low Urin Tract Symptoms. 2015;7(2):71-76. doi:10.1111/luts.12101