First, a descriptive analysis of the population at study will be performed for socio- demographic, anthropometric and clinical characteristics. The means, standard deviations, medians and interquartile ranges will be presented as continuous numerical variables, while the frequencies and percentages will be determined for categorical variables. In the large-scale study, a Chi-square test or Fisher Exact test, if appropriate, will be used for the analysis of the primary endpoint, which is the comparison of the rate of POUR in the Experimental group with the rate of POUR in the Placebo group. This same test will also be helpful in the analysis of the secondary endpoints. If the patient doesn't take all of his medication or his surgery is cancelled he will still be included, since this will be an intention-to-treat analysis. Sub-group analyses will be performed to evaluate the impact of the tumour's characteristics, the duration of the surgery, the volume of intravenous fluids received during the intervention, the type of anaesthesia and the International Prostate Symptom Score (IPSS).