Uroflowmetry: What are its normal values, in which diseases is it performed?

Uroflowmetry (uroflow) test is one of the tests we use frequently in urology. It is very easy to use and does not require any special preparation. Patients only drink water until the feeling of urination (squeezing feeling) comes.

We mostly do it in elderly male patients with lower urinary tract complaints due to prostate enlargement (LUTS). It is a test that we frequently use in patients with suspected neurogenic bladder and urethral stenosis. In this article, I will give general information about the uroflowmetry test.

What is uroflowmetry test?

Uroflowmetry is a test that measures urine flow rate. It shows the amount and speed of urine excreted per second. It is also known as uroflow for short. Uroflow test gives an idea about bladder contraction and sphincter function. The maximum and average values ​​of the current give information about the degree of obstruction.

Which parameters are checked in the uroflowmetry test?

The following measurements are checked in the urine flow test. Among these, the most commonly used average and maximum flow velocity measurements.

  • Maximum flow
  • Time to reach maximum flow
  • Average flow
  • Flow time
  • Total amount of urine made
  • Discharge time

What are the normal values ​​of uroflowmetry in children?

When necessary, uroflowmetry test is also requested in children. The average values ​​for boys and girls are as follows by age;

  • Average flow rate between 4-7 years old is 10 ml/sec.
  • Mean flow rate 12 ml/sec in boys aged 8-13 years
  • Mean flow rate in girls aged 8-13 years is 15 ml/sec.

What are the normal values ​​of the uroflowmetry test in men?

In men, uroflowmetry values ​​change with age. In aging men, the urinary flow rate slows down due to prostate enlargement. In addition, uroflow test results are also low, as bladder contractions will weaken as a natural result of aging and due to reasons such as diabetes. Normal uroflowmetry values ​​in men are as follows according to age;

  • Mean flow rate in men aged 14-45: 21 ml/s
  • Average flow rate in men aged 46-65: 12 ml/s
  • Mean flow rate in men aged 66-80: 9 ml/s

What are the normal values ​​of the uroflowmetry test in women?

Unlike men, uroflowmetry results are not affected much by age in women. Generally, uroflow tests in women remain the same.

  • Average flow rate in women aged 14-45: 18 ml/s
  • Average flow rate in women aged 46-65: 18 ml/s
  • Average flow rate in women aged 66-80: 18 ml/s

Interpretation of the uroflowmetry test

Uroflow is used to evaluate the urinary flow rate due to an obstruction in the urinary tract after the bladder or BPH. We can estimate the degree of obstruction (occlusion, stenosis) according to the maximum flow. According to this;

  • If the maximum flow rate is above 20 ml/s, there is no possibility of an obstruction.
  • If the maximum flow rate is between 15-20 ml/sec, there is a low probability of obstruction. If there is clinical suspicion, it should be investigated.
  • If the maximum flow rate is between 10-15 ml/sec, obstruction is suspected.
  • If the maximum flow rate is less than 10 ml/sec, there is severe obstruction or impaired bladder contractions.
  • The total amount of urine made is also important for a healthy interpretation. If this amount is less than 100 ml, the results should be viewed with suspicion and repeated.

How is the preparation before uroflowmetry?

It is recommended that patients who will undergo uroflowmetry drink water before the procedure. Since some drugs will affect bladder contractions, patients should tell their doctor about the drugs they are using beforehand. If the urologist thinks that these drugs affect bladder functions, he may recommend discontinuing uroflowmetry a few days before. In addition, since the drugs used in the treatment of benign prostate enlargement (BPH) will affect the uroflowmetry results, it is important to discontinue them for a healthy result.

How much water should be drunk for the uroflowmetry test?

In order to obtain a healthy test result, patients must drink enough water beforehand. For a normal uroflow test, an average of 250 cc of urine should be extracted. It is recommended that patients drink 4 glasses of water before the test and not urinate until the feeling of urgency is felt.

How is the uroflowmetry test done?

Before the procedure, patients drink water and are told to squeeze until they feel the urge to urinate. Patients who have a feeling of fullness in the bladder or need to urinate make their urine into a special funnel. The flow rate per second of the urine flowing into this funnel, the time taken for the bladder to empty completely, and the amount of urine flowing per second are connected to an electronic device to which the funnel is connected and recorded. Uroflow test does not have any negative side effects to the patient. It is a test to measure the flow rate of urine during normal urination.

Which  whom uroflowmetry is done?

Uroflowmetry test is performed in patients who have weakened urine flow, who urinate with difficulty and straining, who urinate intermittently and drop by drop, who urinate thin, forked, and who feel that their urine is not fully emptied.

Briefly, uroflowmetry is performed on patients with bladder contraction problems, BPH complaints and suspected urethral stricture. In practice, we usually perform this test in elderly male patients with suspected urethral stricture due to BPH, and neurogenic bladder patients.

In which diseases is the uroflowmetry test low?

It is associated with urinary flow, bladder contraction, and resistance in the urethra after the bladder. For a normal urine flow, the bladder muscle (detrusor muscle) must contract strongly and the pressure in the urethra after the bladder must be low. Uroflowmetry is used in the diagnosis of the following diseases;

  • Neurogenic bladder (flask type neurogenic bladder)
  • Bladder nerve damage due to spinal cord disorders
  • •Diabetes
  • Bladder tumor (bladder cancer)
  • Bladder neck stenosis
  • Bladder neck height
  • Benign prostatic enlargement (BPH)
  • •Prostate cancer
  • urethral stricture
  • Urinary incontinence (incontinence)
  • Patients with frequent cystitis

In which situations is uroflowmetry high?

An increase in urine flow indicates weakness of special muscles called sphincter, which allows urine retention. This may be a sign of urinary incontinence. That is, in patients with urinary incontinence (urinary incontinence), the uroflow test may be high. If uroflow values ​​are low after surgery for prostate cancer or benign prostate enlargement, they return to normal values. If there is permanent damage to the sphincter during these operations, patients will leak urine. In the urine flow study, uroflow values ​​are higher than normal.

Which patients require uroflowmetry in practice?

Patients are generally evaluated by the urologist. Patients are asked about their complaints about urination. Older men often have complaints related to benign prostatic enlargement. Patients who have previously had closed (endoscopic) surgery on the urinary tract may also have complaints (symptoms) related to urethral stenosis or bladder neck stenosis. In general, we request uroflowmetry test to our patients who come with the following complaints;

  • Slowing of urine flow
  • Intermittent, drip urination
  • Sudden cessation while urinating
  • Difficulty starting to urinate
  • Inability to urinate
  • Frequent and sudden need to urinate
  • Patients with urinary incontinence
  • Diabetics with urinary complaints
  • BPH patients
  • Patients with suspected urethral stricture
  • Patients with frequent cystitis

What drugs affect uroflowmetry results?

Some drugs affect the result of uroflowmetry (urine flow test). In order to obtain a healthy result, the urologist asks the patients about the drugs they used before this test and may tell them to stop a few days in advance. These drugs are divided into two main groups;

  • Anticholinergic drugs: This group of drugs prevents the bladder muscle from contracting and as a result, the urine flow slows down. We use these drugs mostly in the treatment of patients with overactive bladder disease.
  • Alpha blocker drugs: Alpha blocker group drugs are used in the treatment of BPH. These drugs work by reducing the pressure in the urinary tract after the bladder.
  • 5-alpha reductase inhibitors (dinasteride, dutastaeride): These drugs are used in the treatment of BPH. By lowering the testosterone level, they shrink the prostate and thus enable patients to urinate comfortably.

What are the conditions that affect the uroflowmetry result?

Apart from drugs, there are some conditions that affect the urine flow test. In this regard, patients should pay attention to these issues in order to obtain a healthy result. The doctor should remind his patients that uroflowmetry will be performed;

  • Excessive straining while urinating
  • Constipation
  • The degree of filling of the bladder
  • Not making excessive body movements while urination

What does residual urine in the bladder indicate after uroflowmetry?

Normally, the bladder needs to be completely emptied after urinating. If the bladder does not empty completely and urine remains in the bladder (residual urine, post-void urine), this indicates that there is an obstruction in the urinary tract after the bladder or that the bladder muscle (detrusor muscle) does not contract (work) sufficiently.

Normally, urine of 100 ml or more is considered abnormal. The greater the obstruction or dysfunction of the bladder muscle, the greater this amount. This condition causes frequent urinary tract infections and requires treatment.

What should be done to increase the urine flow rate?

One of the frequently asked questions by our patients is that their urine flow rates slow down and what they should do to increase it. In male patients, it is considered normal to slow down urine flow with age due to prostate enlargement. If there is no slowdown in urine flow and no improvement with medications and surgery is required. Apart from this, our suggestions to increase the urine flow rate;

  • •Healthy eating
  • •Losing weight
  • Regular sports program (such as walking, running, swimming)
  • Doing Kegel exercises that strengthen the pelvic muscles
  • Sitting urination helps the bladder to empty better and increase the urine flow by pressing the abdominal muscles on the bladder.
  • As the fluid intake increases, the flow rate also increases.

In summary; Uroflowmetry is a test that shows the urine flow rate. In practice, it is mostly performed in patients with benign prostatic enlargement, urethral stricture and neurogenic bladder. In men, it decreases with age due to prostate enlargement. It’s a simple test. It is enough for the patients to drink water until they get stuck. If there are drugs that have been used before and will negatively affect the result, it is better to discontinue them.

Prof. Dr. Emin ÖZBEK

Urology Specialist

Istanbul/ TURKEY

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