From previous studies, the investigators found that sexual outcomes after prostate surgery may show insignificant improvement, remain unchanged or deteriorate in non-negligible number of patients especially those with high preoperative IIEF scores. Deterioration of erectile function could be attributed to persistence of storage symptoms specially nocturia. Several pathophysiologic mechanisms, described before, are involved in pathogenesis of LUTS and ED and one can imagine that after relief of obstruction, the erectile function should improve, however lack of improvement or even deterioration suggests that damage associated with these mechanisms is irreversible and patients may require some sort of penile rehabilitation after surgery. The investigators hypothesized that Tadalafil may enhance relief of storage symptoms and enhance recovery of erectile function after surgery for BPH. With this assumption, a RCT was designed to examine the utility and efficacy of Tadalafil, once daily dose, to relieve persistent/ de novo storage symptoms and early erectile function deterioration after endoscopic prostate surgery.