Introduction: The study aims to identify candidates who can be managed conservatively after the first episode of spontaneous painful acute urinary retention (AUR). Methods: A total of 20 patients with primary spontaneous painful AUR were prospectively included in the study. Twenty-four hours after AUR, the catheter was removed. When residual urinary volume was <100 ml, patients were referred without catheter, when residual urinary volume was ≥100 ml, the catheter was replaced and removed again at day 4, 7 or 10 after AUR, respectively. Receiver operating characteristic curves, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated to assess predictors for successful catheter removal. Results: Thirteen out of 20 (65%) patients had a successful catheter removal until day 10 after AUR. Among them 12 of 13 (93.2%) had a successful catheter removal until day 4 of AUR. Hydronephrosis urinary volume and Qmax at the time of AUR were significant numeric predictors for failure of successful catheter removal. In addition, we calculated a prediction model combing age + prostate volume + urinary volume + Qmax that highly predicts successful catheter removal (sensitivity 100%, specificity 69%, PPV 64%, NPV 100%). Conclusion: We found for the first time a significant association between hydronephrosis and successful catheter removal. Successful catheter removal until day 4 after AUR can safely be managed without immediate transurethral resection of the prostate.