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].