Benign prostatic obstruction (BPO) is one of the most common affections among middle-aged men; it can lead to lower urinary tract (LUT) dysfunction and have a huge impact both on the general health conditions and on the quality of life [1]. In these patients, surgical procedures are often recommended and among them transurethral resection of the prostate (TURP) represents the standard therapy. Still, up to 1/3 of patients keeps experiencing lower urinary tract symptoms (LUTS) after surgery [2]. Detrusor underactivity (DU), detrusor overactivity (DO) and the persistence of benign prostatic obstruction (BPO), together with aging, can influence the surgical result. In particular, DU is recognized as major factor for unsuccessful prostate surgery: treated and untreated patients suffering from DU have similar long-term outcomes after removal of prostatic obstruction [2]. The purpose of this epidemiological study was to analyse post-surgical urodynamics findings of patients who underwent TURP, to assess the prevalence of these urodynamic observation in this population, focusing particularly on the presence of DU and its correlation, if any, with post voiding residual volume (PVR).

Consecutive male patients who underwent a previous surgery for BPO evaluated in three centres with invasive urodynamics (cystometry followed by pressure/flow study, performed according to the ICS standards) for persistence LUTS were included in this study. Data were extracted from databases of three centres and retrospectively analysed. Significant comorbidities, including surgical managed prostate cancer, neurogenic pathologies or suspected/diagnosed LUT pathologies other than BPO, were considered exclusion criteria as well as a urodynamic evaluation performed before than 6 months after surgery. Patients undergoing pharmacological treatment for the LUT dysfunction were included and a separate analysis on their data was performed to determine possible biases due to the therapy. The urodynamic parameters collected in the databases and therefore evaluated were: the presence of DO, DU, determined using the Bladder Contractility Index (BCI: pdetQmax +5Qmax<100), BPO, determined using the Bladder Outlet Obstruction Index (BOOI: pdetQmax -2Qmax>40) [3] and post-voiding residual volume (PVR), considered significant if ≥100 ml. Based on the urodynamic findings, we divided the patients in groups: Normal voiding (N) (BCI≥100, BOOI≤40); BPO (BCI≥100, BOOI>40); DU (BCI<100, BOOI≤40); BPO + DU (BCI<100, BOOI>40); DO; DO coexistent with DU or BPO. To consider the impact of aging, patients were divided in two age groups considering the median age of 70 years and data were analysed.

A total of 79 patients with LUTS after TURP were included. Mean interval between surgery and the urodynamic evaluation was 5.6 (min 0.8 – max 21) years. The median age of the patients was 70 years. Patients were categorized as N (8), O (3), DU (21), DO (20), DU+DO (15), DO+BPO (7), and DO+DU+BPO (2). Forty-nine per cent and 61% of patients showed a urodynamic observation of Detrusor Underactivity and DO, respectively, while residual BPO was present in 16% of patients. A significant PVR (≥100 ml) was found in 33% of patients. Of these patients, 81% showed of a urodynamic observation of DU. None of the patients classified as “Normal” belonged to this group. Few patients presenting a PVR≥100 ml showed a urodynamic observation of BPO (4%) or DO (4%), without DU. We were not able to demonstrate variations in the prevalence of different urodynamic observations in patients aged < or ≥70 years. Patients treated with alpha-blockers did not behave differently in comparison to the other patients.

According to data in literature, persistency of voiding dysfunction following surgery for BPO is not uncommon [1]. This epidemiological study shows that LUTS in patients who underwent a TURP seem to be secondary to the presence of detrusor underactivity or overactivity in the majority of cases (49 and 61% respectively), more than to an effective residual obstruction, present in only 16% of patients. 33% showed a PVR≥100 ml: in these patients, DU was particularly frequent (81%), whilst urodynamic observations of DO or BPO (without an associated DU) were rare (prevalence of 4% for both).

According to this study, LUTS in patients after surgery for BPO are usually associated to DU or DO. The presence of a residual BPO is less common. A cut-off of 100 ml for PVR may be considered useful to identify patients with DU, with 81% of patients with a PVR≥100 ml showing DU and very few (4%) showing BPO or DO. These data may be useful to build a prospective study to define, in men with LUTS post-TURP, a nomogram for the prediction of different urodynamic observations, that may allow a pathophysiological treatment of these patients, avoiding an invasive urodynamic test.

Gravas, S., Bach, T., Drake, M., Gacci, M., Gratzke, C., & Herrmann, T. R. W. “Treatment of non-neurogenic male LUTS.” European Urology Guidelines (EAU). (2017).
Rademakers, Kevin LJ, Gommert A. van Koeveringe, and Matthias Oelke. "Detrusor underactivity in men with lower urinary tract symptoms/benign prostatic obstruction: characterization and potential impact on indications for surgical treatment of the prostate." Current opinion in urology 26.1 (2016): 3-10.
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