Background:The obstructive hydronephrosis is a term that implicates the structural and functional changes of the kidneys as a result of difficulties in the flow of urine. Hydronephrosis specifically describes dilation and swelling of the kidney. Hydronephrosis is a condition that typically occurs when the kidney swells due to the failure of normal drainage of urine from the kidney to the bladder. Our aim was to evaluate the degree of hydronephrosis, causes and diagnostic method. Material andMethods:This is a study of 136 patients that have been treated at the Department of Urology, University Clinical Centre of Kosovo, Prishtina. For diagnosis of hydronephrosis in our patient, we used as equipment the Color Doppler ultrasound, with resolution of 3.5 MHz–8 MHz.Results:Out of 136 participants in the study, 91 (66.9%) were males and 45 (33.1%) females, with significant difference (P=0.000). The average age for males was 49 years old, whereas for females was 33. This study included patients with a diagnosis of symptomatic hydronephrosis with various causes and degrees. All patients were presented with hydronephrosis. The hydronephrosis grade varied from the stage I up to the IV. In our study we have difference grade of hydronephrosis, X2 test, P= 0.114. The most common causes of hydronephrosis in our study were; kidney stone, ureteral stones, neck stenosis PU, pregnancy, infiltrating bladder cancer, bladder neck contracture, prostate adenoma, infiltrating prostatic carcinoma etc. In this study we have indentified different causes, of which stones dominate as the most usual causes of hydronephrosis P= 0.0001.Conclusion:The Ultrasound is an easy method to be applied, non invasive, and a fast one to help and diagnose the obstructive hydronephrosis. The ultrasound has a high sensitivity and should be used as a screening method followed by other methods, as necessary. Hydronphrosis is most commonly presented to men with an average age about fifties. We came to the conclusion that the main causes of hydronephrosis are kidney stone, followed by ureteral stones, in which, in a larger percentage, they appear with the II degree of hydronephrosis.