As surgical therapy for benign prostate hyperplasia (BPH), various surgeries including transurethral resection of prostate (TUR-P) are performed. The purpose of surgery　is　the　improvement　of　the　mechanical　and　functional　obstruction　of　prostatic　urethra. However, urination involves not only prostate but also the extension, contraction, and cooperative movement of bladder. Urodynamic study (UDS) is a useful examination in a diagnosis of the clinical condition and the cause of LUTS. Some patients do not improve their urination after surgery in spite of their UDS results shown obstructive pattern.
Thus we compared urine flow of predicted value estimated by Urodynamic study with measured value after an operation of TUR-P.

Forty-one patients with BPH who performed UDS before TUR-P from 2014 to 2018 at Teikyo University Chiba Medical center were evaluated. At the UDS, maximum urine flow rate (Qmax) and detrusor pressure at Qmax (Pdet@Qmax) were measured. Based on these data, using Schäfer nomogram, we estimated Qmax after TUR-P(EQmax). All surgery was performed by senior residents.
After operation, Qmax was measured by the uroflowmetry (MQmax) and it is compared with EQmax. Secondly, we compared the patients charcteristics and parameters obtained by UDS between the patients with MQmax – EQmax ≥5ml/s or more (Good responder) and MQmax -EQmax≤ -5ml/s (Poor responder) and Intermediate responder (-5ml/s <MQmax -EQmax <5ml/s). All of these studies were performed retrospectively.
Statistical analysis was done by Paired t-test, ANOVA, Mann-Whitney U test and Spearman’s rank correlation.

The median age was 71.5 years old (54-80 years old). The preoperative prostate volume measured by transperitoneal ultrasonography was 55ml (12.8-106 ml). The percentage of patients with urinary retention history was 47.6%. Median EQmax was 18 ml/s (5-32 ml/s), and median MQmax was 14 ml/s (4-40 ml/s). The median MQmax tended to be slightly lower in than that of EQmax (P= 0.054 by Paired t-test). We examined whether is a difference in MQmax value among the grade of obstruction and detrusor contractility. However, there was no significant difference in the MQmax in each grade of Schäfer nomogram.
Secondly, we compared the parameter among Good, Intermediate and Poor responder group (Table 1). Statistical analysis by one-way ANOVA among the three groups, Detrusor Pressure at Qmax(Pdet＠Qmax), EQmax, MQmax and Postoperative Voided Volume were significantly different. There was a significant difference between Good responder group and Intermediate responder group in the MQmax (P < 0.001 by Mann-Whitney U test). In the comparison of Poor responder group and Intermediate responder group, Poor responder is significantly older than Intermediate group patients (P = 0.003 by Mann-Whitney U test). In Poor responder group, Pdet＠Qmax and EQmax were significantly higher and MQmax is significantly lower and bladder capacity tends to be low.

MQmax was significantly better in Good responder group. In Good responder group, the volume of prostate, resected prostate volume and the proportion of resected volume of prostate (Resected / Preoperative prostate volume) were tend to be more than other groups. It seems that good Qmax would be expected by resected larger volume in the patients with large prostate.
In the Poor responder group, Pdet@Qmax was higher in spite of their poor response. Two hypotheses might be considered. 
1 .Age might be a factor that causes poor therapeutic effect. Bladder capacity is negatively related age (r=-0.362 by Spearman’s rank correlation) (Figure 1). Decreased bladder capacity caused by aging might be affected low MQmax. 
2. There was a possibility that sufficient resection was not done in poor responder group. The proportion of resected volume to preoperative prostate volume in poor response group was lower than other groups. It was not significant, but we think it was important.
The limitation of this study was small number of patients and retrospective study.

The median EQmax obtained by UDS was smaller than the MQmax after TUR-P. There were some cases in which there was a large difference from predicted value. By excising adequately for larger adenomas, better urination can be expected. In addition, it was suggested that older age may be a factor that causes worse results of Qmax than predicted.