Voiding symptoms in men, such as a poor voiding stream, prolonged bladder emptying and increased post-void residual may be the result of bladder outlet obstruction (BOO) due to benign prostatic obstruction (BPO) or impaired bladder contractility due to detrusor underactivity (DU) (1). A pressure-flow study is the only method to distinguish between BPO and DU. In patients with BPO, transurethral resection of the prostate (TURP) is performed, but many urologists hesitate to perform a TURP in patients with DU since clinical improvement may be poor and surgery bears considerable risks. The question is: is this hesitation justified? The aim of this study was to compare clinical outcomes after TURP in men with and without DU using the Hannover-Maastricht (HM)-nomogram, a BOO-dependent bladder contractility nomogram (2). To our knowledge this is the first clinical report of men with and without DU treated with TURP using the HM-nomogram for categorization of bladder contractility.

In this retrospective analysis we studied men treated with TURP for refractory voiding symptoms between 2010 and 2016. A total of 394 of these men underwent a preoperative pressure-flow study (PFS). In our final analysis we only included patients with a reliable preoperative PFS, a pre- and postoperative maximum flow rate (Qmax) and pre- and postoperatively measurement of post-void residual (PVR) (n=80). Bladder outlet obstruction index (BOOI) and maximum Watt factor (Wmax) were calculated by the software (MMS) of the PFS . Patients were plotted in the HM-nomogram and categorized in the group with DU (<25th percentile group) and without DU (the >25th percentile group). Clinical outcomes were measured by comparing pre- and postoperative Qmax and PVR. Catheterization rates were calculated pre- and postoperatively in both groups, but irrespective of method of catheterization. 
Different TURP methods used in our hospital included: GreenLight™ laser vaporization, 980-nm diode laser vaporization and electrosurgical TURP. The choice for electrosurgical TURP was the inability to visualize the ureteral orifices. Patients with presence of a large prostatic midlobe were mostly treated with 980-nm diode laser vaporization. All other patients were treated with GreenLight™ laser vaporization. Statistical analysis was performed using a Mann-Whitney U test and Chi-square test using SPSS version 23.

Baseline data of preoperative pressure-flow studies of men with or without detrusor underactivity are shown in table 1. Clinical outcomes before and six weeks after TURP are shown in table 2. Pre- and postoperative catheterization rates are shown in table 3. 
Postoperative Qmax increased dramatically after TURP in men with and without DU, but was not significantly affected by the method of TURP (p=0.36). However, patients who underwent a 980-nm diode laser vaporization had a significantly higher postoperative PVR (33ml (10-70)) than GreenLight™ laser vaporization (11ml (0-40)) and electrosurgical TURP (0ml (0-42)) (p=0.02).

This is the first clinical report on TURP in men with and without DU using the HM-nomogram for categorization of bladder contractility. At baseline cystometric capacity, voided volume, Qmax, PVR, voiding efficiency, first desire, BCI and Wmax were significantly different between men with and without DU. Age, BOOI, pDetQmax and voiding time did not differ significantly between both groups. Except for age, Qmax and voided volume these data are in line with previously published data on the HM-nomogram (2). An explanation for the differences of our findings and previous work (2) may be that a selection bias occurred towards patients with more severe symptoms requiring a pressure-flow study and/or desobstructive prostate surgery.
In both groups postoperative Qmax improved, PVR and the need for catheterization decreased, without significant differences between men with and without DU. Since we only included men with a reliable preoperative PFS, pre- and postoperative Qmax and PVR, there might also have been a selection bias towards patients with a less severe form of DU, because patients with missing data of Qmax and PVR were excluded from analysis.

In this retrospective analysis, TURP for refractory voiding symptoms leads to improvement of the Qmax, reduction of the PVR and the catheterization rate in patients with and without detrusor underactivity. Therefore TURP should also be considered as a viable treatment option in patients with detrusor underactivity.

Abrams P, Cardozo L, Fall M, et al. The standardisation of terminology of lower urinary tract function: Report from the standardisation sub-committee of the international continence society. American Journal of Obstetrics and Gynecology 2002; 187:116-126.
Oelke M, Rademakers K, van Koeveringe G. Unravelling Detrusor Underactivity: Development of a Bladder Outlet Resistance – Bladder Contractility Nomogram for Adult Male Patients With Lower Urinary Tract Symptoms. Neurourology and Urodynamics 2016; 35:980-986.