Benign prostatic hyperplasia (BPH) is a common condition in aging males which often causes bladder outlet obstruction (BOO) with negative impact on male lower urinary tract symptoms.Although preoperative urodynamic study is not mandatory for BPH surgery, it is commonly utilized to evaluate the degree of obstruction (bladder outlet obstruction index; BOOI) and detrusor contractility (bladder contractility index; BCI), and predict surgical outcomes. Both indexes use detrusor pressure at maximal flow rate (PdetQmax) and maximal flow rate (Qmax) during voiding cystometry. To minimize the artifact and errors, voiding pressures should be analyzed when the patient is sufficiently relaxed and involuntary bladder contraction should not be used for calculating the pressure-flow relationship. However, there are some patients who present similar patterns between detrusor overactivity (DO) and detrusor pressure (Pdet) during voiding despite repeated measurement.
Our hypothesis is that patients who present similar patterns between DO and Pdet during voiding might depend on DO or urge to void (although their uninhibited urge to void is denied during pressure-flow study) so the real Pdet of such patients could be overestimated. Thus, those patients might present different clinical characteristics and surgical outcomes after BPH surgery. The aim of present study was to investigate whether similar patterns of DO and Pdet during voiding on preoperative urodynamic study would affect clinical outcomes after holmium laser enucleation (HoLEP) in BPH patients

Patients who underwent HoLEP for BPH between 2009 and 2020 were reviewed. Those who with positive DO on preoperative urodynamic study were included. Any patients with prior diagnosis of prostate/bladder cancer, neurogenic bladder, or preoperative urethral stricture were excluded. 
DO patterns were compared with patterns of Pdet during voiding. Group A presented similar patterns (shape and amplitude) between DO and Pdet, while Group B presented different patterns (Figure 1). Baseline demographics, perioperative findings were compared between Group A and B, based on the routine protocol for BPH.

A total of 256 patients were included with mean age of 69.7 ± 6.3 years with median follow-up of 49.2 (range: 1.2 – 259.2) months. Based on DO patterns, 34 patients were assigned to Group A (similarity patterns between DO and Pdet during voiding) and others (n=222) were categorized into Group B. There were no significant differences in age, underlying diseases and preoperative prostate volume on TRUS. However, Group A was less exposed to BPH medication before surgery and acute urinary retention was more frequent (41.2% vs. 24.8%, p = 0.045) than Group B. Meanwhile, there were no differences in duration and types of medication in those who patients were under medical therapy. 
After excluding patients with recurrent urinary retention and recent history of urinary tract infection, complete preoperative 3-day voiding diary was available in 124 patients (124 out of 177, 70.1%). There were no differences in mean episodes of daily frequency, urgency and urgency urinary incontinence between groups. IPSS total score (mean: 21.6 ± 10.9) did not differ (22.9 ± 8.3 vs. 21.3 ± 11.3, p =0.248). IPSS QoL (quality of life) score was higher in Group A (4.6 ± 1.2 vs. 4.0 ± 1.3, p = 0.037).
Patients in Group A had smaller voided volume in both uroflowmetry and voiding cystometry. First sensation and detrusor overactivity was observed in smaller volume, but maximum amplitude of DO was higher. All patients in Group A succeeded in voiding at voiding cystometry with larger MaxPdet (maxium detrusor pressure) and PdetQmax. Both groups presented mean BOOI (PdetQmas – 2 * Qmax) larger than 40, but BOOI was higher in Group A. Smaller proportion of patients had DU defined as BCI (PdetQmax + 5 * Qmax) less than 100 but not statistically significant (26.5% vs. 40.5%, p = 0.120)

BOO surgery successfully improved voiding profiles on uroflowmetry, IPSS symptom scores (21.5 ± 12.3 to 8.4 ± 6.1, p < 0.001) and QoL scores (4.0 ± 1.3 to 1.8 ± 1.4, p < 0.001). Effects of BOO surgery were additionally assessed after dividing patients in to four categories (1. DUA (-) Group A; 2. DUA (-), Group B; 3. DUA (+) Group A; 4. DUA (+) Group B). On postoperative 1 month and 6-month uroflowmetry/bladder scan, voided volume, Qmax and post-void residual volume were significantly improved except for patients in category 3; DUA (+) Group A (Table 1).

The present study investigated the impact of similar patterns of DO and Pdet in preoperative urodynamic study on clinical outcomes after HoLEP. Patients with similar patterns presented small bladder capacity and voided volume. In addition, DO was provoked in smaller volume with higher amplitude that MaxPdet and PdetQmax value was larger leading to higher BCI and BOOI than those with different patterns. Postoperatively, patients with DU and similar patterns did not show significant improvement in uroflowmetry. However, this study is limited by the retrospective study design.

BPH patients with similar patterns between preoperative DO and Pdet during voiding were more naïve to medical therapy with more episodes of urinary retention and smaller functional capacity. Therapeutic effects of HoLEP was limited if such patients had concurrent DU.