Detrusor Underactivity (DU) is a common but still poorly understood and underdiagnosed urological problem. 
Effectiveness of TURP is uncertain in men with DU and until a few years ago was considered a contraindication for surgery. 
With this study we investigate the role of DU on recovery voiding in men with Indwelling Catheter (IC) or in Clean Intermittent Catheterization (CIC) eligible to TURP

This is an observational, prospective, non-randomized study that started in 2017 and completed in 2025. 
Pts with IC or in CIC for PVR>300 ml and BVE<50%, eligible to TURP, were recruited in the study. All pts underwent UD, IPSS and BII prior to surgery. 
Exclusion criteria: neurological diseases, previous TURP and/or pelvic irradiation.
Q-Max, BVE, Bladder Contractility Index (BCI) and Bladder Outlet Obstruction Index (BOOI) were determined, allowing to categorize pts in 4 groups: 
Group A: pts with DU and BOO (BCI<100 and BOOI>40).
Group B: pts with DU (BCI<100 and BOOI<40)
Group C: pts with Contractile Underactive Bladder, with a detrusor contraction <40 cmH2O, but no flow detected (no BCI nor BOOI determined because of absence of flow)
Group D: pts with Acontractile Bladder (no detrusor contraction nor flow detected during UD).
We followed operated pts after TURP verifying recovery of BVE, Q-Max and PVR, IPSS and BII 1-6 and one year after surgery

We included in the study 186 pts, 72 pts for group A (BCI 79 +/- 11 and BOOI 54 +/- 9), 56 pts for group B (BCI 59 +/- 15 BOOI 22 +/- 12), 30 pts in group C and 28 pts in group D (BCI and BOOI not determined).
We excluded 45 pts with a normal detrusor contraction (> 40 cmH2O) but no flow detected at UD because a severe BOO.  
All pts in group A- B and C underwent TURP, all pts but 8 of group D remained in CIC or IC, 8 highly motivated pts of group D underwent surgery after given very well informed consent. 
After surgery 70 patients of group A (97%) regained micturition without necessity of CIC, 2 (3%) pts restored micturition but continued with one daily CIC for complete bladder emptying. 
In group B 44 pts (80%) restored micturition after surgery without necessity of CIC, 9 (15%) regained spontaneous void but continued with 1-2 daily CIC for complete emptying, 3 pts (5%) did not restore spontaneous void so remained in CIC. 
Pts in group B who did not regain satisfying bladder emptying with BVE50% presented preoperatively a severe DU with BCI<40 
In group C 21 pts (70%) restored micturition without necessity of CIC, 4 pts (14%) needed 1 daily CIC for complete voiding and 5 pts (16%) did not restore micturition and remained in CIC or IC. 
Pts in group C who did not restore micturition presented severe DU with contraction <20 cmH2O
Among 8 out of 28 pts of group C who underwent surgery although acontractility diagnosis only 3 pts restored micturition but needed to continue 2 daily CIC to complete bladder emptying. 
After surgery patients in the three groups (A, B and C) showed a statistical significant improvement in IPSS, BII score, Q-max and PVR (Table 1)

Definition of DU is not clear especially in patients without flow registration at UD. For this reason we decide to include patients with DU without flow detected and verifying surgery results in such cases. 
DU could not be a contraindication to TURP allowing in most cases to restore spontaneously voiding and satisfying bladder emptying.

DU do not controindicate in most cases TURP,  acontractility and severe underactivity only could result in a surgical failure.

Abrams P. Bladder outlet obstruction index, bladder contractility index and bladder voiding efficiency: three simple indices to define bladder voiding function. BJU Int. 1999 Jul;84(1)