Aim: The aim of this study was to investigate the relationship between the degree of hydronephrosis and the presence of microscopic hematuria in patients that presented to the emergency department (ED) with ureteral stones. Methods: The records of patients who presented to our ED due to urolithiasis between January 2017 and December 2020 were retrospectively analyzed. Patients aged 18 years or older who underwent non-contrast computed tomography (CT abdomen/pelvis) and urinalysis (UA) and were diagnosed with ureteral stones were included in the study. Radiology reports were reviewed for stone size, localization, and degree of hydronephrosis. Patients with and without microscopic hematuria and the degree of hydronephrosis were compared. Results: A total of 476 patients were included, which consisted of 391 with microscopic hematuria and 85 without microscopic hematuria. The median stone size was 4.1 mm in the presence of microscopic hematuria and 5.5 mm in the absence of microscopic hematuria. Logistic regression analysis was performed to determine the factors associated with the development of hydronephrosis. Stone size [odds ratio (OR):2.15, 95% confidence interval (CI):1.12-4.16, p<0.001), presence of pyuria (OR: 2.58, 95%CI: 1.78-3.48, p<0.001), and absence of microscopic hematuria (OR: 1.31, 95%CI 1.04-2.89, p=0.017) were identified as risk factors for moderate and severe hydronephrosis. Conclusion: We consider that non-contrast CT imaging is necessary for the diagnosis and treatment of emergency cases in which microscopic hematuria is not detected in urinalysis since their stone size may be larger and degree of hydronephrosis may be more severe.