Flow Rate and Residual Ultrasound

As part of the investigation of problems with bladder function, it is often necessary to measure the rate at which urine is passed (the flow rate), and the amount of urine left in the bladder (the residual).

To get a good flow test you need to pass more than 150 mL of urine. Begin drinking water early on the day, unless you already drink a moderate amount of water, as you need to have a full bladder for the test. To achieve this it is suggested that you:

1. Drink plenty of water on waking
2. Pass urine two hours before the test 
3. Continue to drink approximately 4-5 drinks before your appointment

If you do not have a full bladder at the time you come for the test, you can drink water in the waiting room to fill your bladder. You may be asked to fill out a simple questionnaire upon arrival.

When you have a full bladder and feel as though you are ready to pass urine, press the button in the waiting room to alert the nurse. They will ask you to pass urine into a special toilet which measures the rate and volume of your flow.

You will then be asked to lie down on a bed for a quick ultrasound scan of your bladder. 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.

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Our team of specialists combine to deliver excellence in urology healthcare. We offer the greatest breadth of urological expertise of any urology practice in New Zealand. As well as caring for the urological problems of men such as prostate cancer and sexual dysfunction, we also offer comprehensive treatment of female urology and pelvic health as well as the care of children.

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