Objective: This paper aims to estimate the incidence of post-obstructive diuresis (POD) among patients with urinary retention, explore possible underlying causes and identify patients who need hospitalization.Material and methods: This retrospective study includes patients admitted for urinary retention in Zealand University Hospital, Denmark. We collected demographic characteristics, health information and laboratory results from patients' charts and analyzed data statistically.Results: We assessed 64 patients, and POD occurred in 29.7%. A significant correlation was observed between POD and residual urine, serum creatinine, serum urea and systolic and diastolic blood pressure. We identified increased residual urine volume as an independent predictor of POD by OR 1.21 (95% CI: 1.06-1.40), p = 0.006 per 100 mL and creatinine of >120 umol/L is an independent predictor of POD by OR 7.17 (95% CI; 1.63-31.37), p = 0.009. Patients with residual urine at the time of diagnosis of more than 1150 ml will suffer POD with a probability of area under curve (AUC) 0.874 (p < 0.001) with 84% sensitivity and 78% specificity. Patients with creatinine >120 umol/L will suffer POD with a probability of AUC 0.774 (p < 0.001) with 68% sensitivity and 82% specificity.Conclusion: In this small retrospective study residual urine of more than 1150 mL and elevated creatinine are independent predictors of POD in patients with urinary retention. However, larger prospective studies are needed to confirm these findings.