For this test, you will urinate into a special funnel that is connected to a measuring instrument. The instrument calculates the amount of urine, rate of flow in seconds, and the length of time until all urine has been passed. This information helps evaluate how well the lower urinary tract is working. It also helps figure out if there is a blockage of normal urine outflow (termed Bladder Outlet Obstruction, BOO)
An ultrasound scan of the bladder is required after you have completed you urine flow test. This is a painless scan where ultrasound gel is placed on your lower abdomen, then the ultrasound probe uses sound waves to produce an image to see how much urine is left in your bladder.
To get a good flow test you need to pass more than 150 mL of urine. To prepare it is best to drink plenty of water two hours before your test.