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Uroflowmetry

Definition

Uroflowmetry is a test that measures the volume of urine released from the body, the speed with which it is released, and how long the release takes.

Alternative Names

Uroflow

How the test is performed

You will urinate in a special urinal or toilet with a machine that has a measuring device.

You will be asked to begin urinating after the machine has started. When you finish, the machine will create a report for your health care provider.

How to prepare for the test

Your health care provider may ask you to temporarily stop taking medications that can affect the test results.

Uroflowmetry is best done when you have a full bladder. Do not urinate for 2 hours before the test. Drink extra fluids so you will have plenty of urine for the test.

Do not place any toilet tissue in the test machine.

How the test will feel

The test involves normal urination, so you should not experience any discomfort.

Why the test is performed

This test is useful in evaluating the function of the urinary tract. Usually, a patient having this test will report urination that is too slow.

Normal Values

Normal values vary depending on age and sex. In men, urine flow declines with age. Women have less change with age:

• Ages 4 - 7
  • The average flow rate for both males and females is 10 mL/sec.
• Ages 8 - 13
  • The average flow rate for males is 12 mL/sec.
  • The average flow rate for females is 15 mL/sec.
• Ages 14 - 45
  • The average flow rate for males is 21 mL/sec.
  • The average flow rate for females is 18 mL/sec.
• Ages 46 - 65
  • The average flow rate for males is 12 mL/sec.
  • The average flow rate for females is 18 mL/sec.
• Ages 66 - 80
  • The average flow rate for males is 9 mL/sec.
  • The average flow rate for females is 18 mL/sec.

What abnormal results mean

Results are compared with your symptoms and physical exam. A result that may need treatment in one patient may not need treatment in another patient.

Several circular muscles normally regulate urine flow. If any of these muscles becomes weak or stops working, you may have an increase in urine flow or urinary incontinence.

If there is a bladder outlet obstruction or if the bladder muscle is weak, you may have a decrease in urine flow. The amount of urine that remains in your bladder after urinating can be measured with ultrasound.

Your health care provider should explain and discuss any abnormal results with you.

What the risks are

There are no risks with this test.

Special considerations

References

Peterson AC, Webster GD. Urodynamic and videourodynamic evaluation of voiding dysfunction. In: Wein AJ, ed. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 58.