To develop an ultrasound (US)-based method for noninvasive diagnosing of bladder outlet obstruction, and the relationship between decorrelation of sequential US images and the degree of obstruction in a urethra model was studied.A flexible model of a male urethra was constructed from 15\% aqueous solution of polyvinyl alcohol cryogel. To create 4 different degrees of obstruction, polyvinyl alcohol rings representing the prostate were placed around the model. Each model was perfused at different flow rates (1-15 mL/s) with an aqueous solution containing scattering particles mimicking urine. At each flow rate, 10 sequential US images were acquired. The average correlation coefficients between the images were calculated and plotted as a function of the degree of obstruction and the flow rate.The average correlation decreased approximately linearly with an increase in the degree of obstruction. This decrease in correlation (decorrelation) might be due to turbulence caused by the obstruction. A higher degree of obstruction creates more turbulence and results in a higher decorrelation between sequential US images.Quantification of the decorrelation between sequential US images may provide us with a new approach to noninvasively diagnose bladder outlet obstruction.