- Objectives In this study we assessed the possible influence of dutasteride (types 1 and 2 isoenzymes of 5-alpha-reductase inhibitors) on prostate tissue vascularity. We also attempted to evaluate whether preoperative treatment with dutasteride could help to avoid excessive bleeding in patients undergoing transurethral resection of prostate (TUR-P). Methods This pilot study has 3 phases. All patients enrolled in the study had a prostate-specific antigen < 4 ng/mL and normal digital rectal examination. In the first phase we included 10 patients with benign prostatic hyperplasia treated with alpha-blockers. The end point of this phase was to choose the preset that could exclude noise signals and be reproducible. In the second phase, we included 32 patients in whom color Doppler sonography (CDS) was performed before and 6 weeks after treatment with 0.5 mg dutasteride per day. We counted every discrete color Doppler signal (CD-spot). To compare the CDS data, we used the Student t test, and P < .05 was considered significant. Afterward, 46 patients joined the third phase. Patients were assigned to the control and study groups according to sequentially numbered sealed envelopes. Patients in the study group received 0.5 mg dutasteride 6 weeks before TUR-P. Results In the first phase: color Doppler preset with pulse repetition frequency of 0.3 kHz was chosen as the most sensible. In the second phase, a significant decline in CD-spots count was detected in 23 (72%) patients (P < .05) and was more distinctive in the periurethral zone. In the third phase, only 43 of the patients continued with TUR-P (in 3 patients, voiding symptoms improved). Operating time and volume of irrigation fluid were significantly different (50.55 minutes/42.65 minutes, P = .014; 8.03/13.10 L, P = .047). Conclusions Six weeks of dutasteride treatment may reduce prostate tissue vascularity in the periurethral area proximal to the verumontanum. The third phase of our study confirmed that preoperative treatment with dutasteride could improve operative performance and avoid TUR syndrome.