Background: Detrusor underactivity (DU) is a frequent clinical issue that is poorly understood. Both the diagnosis and the course of treatment are challenging and unpredictable. In men, DU and bladder outlet obstruction (BOO) frequently coexist. Prostatic surgery may enhance voiding efficiency (VE). Aim: Toimprove the outcome of transurethral resection of the prostate (TURP) by selectingBenign Prostatic Hyperplasia (BPH) patient with significant post-voiding residual urine who could benefit from surgery and could void normally after TURP. Patients and methods: This is a clinical trial – single arm studyincluded 24 male patients above 50 years oldwith BPH and significant postvoiding residual urine who underwent TURP. Urodynamic predictors were assessed. Results: There was significant difference between patients with good and poor outcomes regarding IPSS pre-operatively, Qmax, postvoid residual (PVR), Voiding Efficiency and BCI Conclusion: The success rate of prostatectomy was 83.3% and about 16.7% had poor outcomes. Patients with higher BCI had good prognosis.