Urodynamic Testing

National Kidney and Urologic Diseases Information Clearinghouse 

What is the urinary tract? 

The urinary tract is the body’s drainage 

system for removing wastes and extra water. 

The urinary tract includes two kidneys, two 

ureters, a bladder, and a urethra. Blood 

flows through the kidneys, and the kidneys 

filter out wastes and extra water, making 

urine. The urine travels down two narrow 

tubes called the ureters. The urine is then 

stored in a muscular, balloonlike organ called 

the bladder. The bladder swells into a round 

shape when it is full and gets smaller as it 

empties. When the bladder empties, urine 

flows out of the body through the urethra. 

What is the lower urinary 

tract and how does it work? 

The lower urinary tract includes the bladder 

and urethra. The bladder sits in the pelvis 

and is attached to other organs, muscles, and 

the pelvic bones, which hold it in place. The 

urethra is a tube at the bottom of the bladder that carries urine from the bladder to the 

outside of the body. 

The lower urinary tract works by coordinating the muscles of the bladder wall with the 

sphincters, which are circular muscles that 

surround the area of the bladder that opens 

into the urethra. The muscles of the bladder wall relax as the bladder fills with urine. 

If the urinary tract is healthy, the bladder 

can hold up to 2 cups, or 16 ounces, of urine 

comfortably for 2 to 5 hours. The sphincters 

close tightly like rubber bands around the 

bladder to help keep urine from leaking. As 

the bladder fills, the need to urinate becomes 

stronger and stronger, until the bladder 

reaches its limit. Urination is the process 

of emptying the bladder. To urinate, the 

brain signals the bladder muscles to tighten, 

squeezing urine out of the bladder. At the 

same time, the brain signals the sphincters 

to relax. As the sphincters relax, urine exits 

the bladder through the urethra. When all 

the signals occur in the correct order, normal 

urination occurs. 

For more information about the urinary tract 

and urinary tract problems, see the National 

Kidney and Urologic Diseases Information 

Clearinghouse (NKUDIC) fact sheet The 

Urinary Tract. 

U.S. Department 

of Health and 

Human Services 

NATIONAL 

INSTITUTES 

OF HEALTH 

             

              

             

              

             

             

              

                

             

                

                   

            

             

             

                

               

                  

                 

                 

     

           

                 

           

               

              

                  

               

                     

                

             

                

               

           

              

              

             

                

             

                

              

               

             

             

       

       

Kidneys 

Bladder 

Sphincters 

Urethra 

Pelvic floor 

muscles 

Ureters 

Front view of the urinary tract 
           

           

                   

          

                   

           

   

     

       

     

   

           

          

           

               

          

             

                

         

                   

                

             

               

               

                 

                  

               

                

               

                 

           

        

             

     

           

             

              

           

               

            

           

            

       

           

              

     

   

     

     

           

         

       

         

         

      

               

                   

             

                 

            

         

           

           

             

              

             

       

              

               

       

What is urodynamic testing? 

Urodynamic testing is any procedure that 

looks at how well the bladder, sphincters, 

and urethra are storing and releasing urine. 

Most urodynamic tests focus on the bladder’s 

ability to hold urine and empty steadily and 

completely. Urodynamic tests can also show 

whether the bladder is having involuntary 

contractions that cause urine leakage. A 

health care provider may recommend urodynamic tests if symptoms suggest problems 

with the lower urinary tract. Lower urinary 

tract symptoms (LUTS) include 

• urine leakage 

• frequent urination 

• painful urination 

• sudden, strong urges to urinate 

• problems starting a urine stream 

• problems emptying the bladder
 

completely
 

• recurrent urinary tract infections 

Urodynamic tests range from simple observation to precise measurements using sophisticated instruments. For simple observation, 

a health care provider may record the length 

of time it takes a person to produce a urinary 

stream, note the volume of urine produced, 

and record the ability or inability to stop the 

urine flow in midstream. For precise measurements, imaging equipment takes pictures 

of the bladder filling and emptying, pressure monitors record the pressures inside 

the bladder, and sensors record muscle and 

nerve activity. The health care provider will 

decide the type of urodynamic test based 

on the person’s health information, physical exam, and LUTS. The urodynamic test 

results help diagnose the cause and nature of 

a lower urinary tract problem. 

Most urodynamic tests do not involve special 

preparations, though some tests may require 

a person to make a change in fluid intake or 

to stop taking certain medications. Depending on the test, a person may be instructed to 

arrive for testing with a full bladder. 

What are the urodynamic 

tests? 

Urodynamic tests include 

• uroflowmetry 

• postvoid residual measurement 

• cystometric test 

• leak point pressure measurement 

• pressure flow study 

• electromyography 

• video urodynamic tests 

Uroflowmetry 

Uroflowmetry is the measurement of urine 

speed and volume. Special equipment 

automatically measures the amount of urine 

and the flow rate—how fast the urine comes 

out. Uroflowmetry equipment includes a 

device for catching and measuring urine and 

a computer to record the data. During a 

uroflowmetry test, the person urinates privately into a special toilet or funnel that has a 

container for collecting the urine and a scale. 

The equipment creates a graph that shows 

changes in flow rate from second to second 

so the health care provider can see when 

the flow rate is the highest and how many 

seconds it takes to get there. Results of this 

test will be abnormal if the bladder muscles 

are weak or urine flow is blocked. Another 

approach to measuring flow rate is to record 

the time it takes to urinate into a special container that accurately measures the volume 

of urine. Uroflowmetry measurements are 

performed in a health care provider’s office; 

no anesthesia is needed. 

2  Urodynamic Testing 
             

             

                 

                   

                

            

              

             

            

           

           

                

               

             

                

               

              

               

               

              

        

             

             

         

                

             

            

         

                 

          

           

               

           

               

             

              

             

               

              

             

                 

        

             

         

Uroflowmetry equipment 

Postvoid Residual Measurement 

This urodynamic test measures the amount 

of urine left in the bladder after urination. 

The remaining urine is called the postvoid 

residual. Postvoid residual can be measured 

with ultrasound equipment that uses harmless sound waves to create a picture of the 

bladder. Bladder ultrasounds are performed 

in a health care provider’s office, radiology center, or hospital by a specially trained 

technician and interpreted by a doctor, usually a radiologist. Anesthesia is not needed. 

Postvoid residual can also be measured using 

a catheter—a thin flexible tube. A health 

care provider inserts the catheter through the 

urethra up into the bladder to remove and 

measure the amount of remaining urine. A 

postvoid residual of 100 milliliters or more 

is a sign that the bladder is not emptying 

completely. Catheter measurements are 

performed in a health care provider’s office, 

clinic, or hospital with local anesthesia. 

Cystometric Test 

A cystometric test measures how much urine 

the bladder can hold, how much pressure 

builds up inside the bladder as it stores urine, 

and how full it is when the urge to urinate 

begins. A catheter is used to empty the 

bladder completely. Then a special, smaller 

catheter is placed in the bladder. This catheter has a pressure-measuring device called a 

manometer. Another catheter may be placed 

in the rectum to record pressure there. 

Once the bladder is emptied completely, 

the bladder is filled slowly with warm water. 

During this time, the person is asked to 

describe how the bladder feels and indicate 

when the need to urinate arises. When the 

urge to urinate occurs, the volume of water 

and the bladder pressure are recorded. The 

person may be asked to cough or strain 

during this procedure to see if the bladder 

pressure changes. A cystometric test can also 

identify involuntary bladder contractions. 

Cystometric tests are performed in a health 

care provider’s office, clinic, or hospital with 

local anesthesia. 

Urethra 

Catheter 

Bladder 

Cystometric test 

3  Urodynamic Testing 
             

          

                 

               

              

                

             

         

        

               

           

              

                

                 

         

             

            

                

                 

             

                    

             

         

              

               

               

                

               

           

            

             

             

           

          

               

               

   

         

             

                  

           

           

            

              

           

                

             

             

             

                

         

             

             

              

           

               

              

           

             

          

               

               

          

               

             

         

             

               

              

             

Leak Point Pressure 

Measurement 

This urodynamic test measures pressure at 

the point of leakage during a cystometric 

test. While the bladder is being filled for the 

cystometric test, it may suddenly contract 

and squeeze some water out without warning. The manometer measures the pressure 

inside the bladder when this leakage occurs. 

This reading may provide information about 

the kind of bladder problem that exists. The 

person may be asked to apply abdominal 

pressure to the bladder by coughing, shifting 

position, or trying to exhale while holding 

the nose and mouth. These actions help the 

health care provider evaluate the sphincters. 

Pressure Flow Study 

A pressure flow study measures the bladder 

pressure required to urinate and the flow 

rate a given pressure generates. After the 

cystometric test, the person empties the bladder, during which time a manometer is used 

to measure bladder pressure and flow rate. 

This pressure flow study helps identify bladder outlet blockage that men may experience 

with prostate enlargement. Bladder outlet 

blockage is less common in women but can 

occur with a cystocele or, rarely, after a surgical procedure for urinary incontinence. Pressure flow studies are performed in a health 

care provider’s office, clinic, or hospital with 

local anesthesia. 

Electromyography 

Electromyography uses special sensors to 

measure the electrical activity of the muscles 

and nerves in and around the bladder and 

the sphincters. If the health care provider 

thinks the urinary problem is related to 

nerve or muscle damage, the person may 

be given an electromyography. The sensors are placed on the skin near the urethra 

and rectum or on a urethral or rectal catheter. Muscle and nerve activity is recorded 

on a machine. The patterns of the nerve 

impulses show whether the messages sent to 

the bladder and sphincters are coordinated 

correctly. Electromyography is performed 

by a specially trained technician in a health 

care provider’s office, outpatient clinic, or 

hospital. Anesthesia is not needed if sensors 

are placed on the skin. Local anesthesia is 

needed if sensors are placed on a urethral or 

rectal catheter. 

Video Urodynamic Tests 

Video urodynamic tests take pictures and 

videos of the bladder during filling and 

emptying. The imaging equipment may use 

x rays or ultrasound. If x-ray equipment is 

used, the bladder will be filled with a special 

fluid, called contrast medium, that shows up 

on x rays. X rays are performed by an x-ray 

technician in a health care provider’s office, 

outpatient facility, or hospital; anesthesia 

is not needed. If ultrasound equipment is 

used, the bladder is filled with warm water 

and harmless sound waves are used to create 

a picture of the bladder. The pictures and 

videos show the size and shape of the bladder 

and help the health care provider understand the problem. Bladder ultrasounds are 

performed in a health care provider’s office, 

radiology center, or hospital by a specially 

trained technician and interpreted by a doctor, usually a radiologist. Although anesthesia is not needed for the ultrasound, local 

anesthesia is needed to insert the catheter to 

fill the bladder. 

4  Urodynamic Testing 
     

     

         

       

     

             

      

               

           

             

               

             

         

                 

           

             

        

             

           

          

           

       

           

         

       

            

       

           

        

         

        

         

    

           

   

             

               

            

                 

            

             

               

         

               

                

       

             

   

             

       

                

         

                 

                

             

               

           

             

   

         

             

           

             

             

   

What happens after 

urodynamic tests? 

After having urodynamic tests, a person may 

feel mild discomfort for a few hours when 

urinating. Drinking an 8-ounce glass of 

water every half-hour for 2 hours may help to 

reduce the discomfort. The health care provider may recommend taking a warm bath 

or holding a warm, damp washcloth over the 

urethral opening to relieve the discomfort. 

An antibiotic may be prescribed for 1 or 

2 days to prevent infection, but not always. 

People with signs of infection—including 

pain, chills, or fever—should call their health 

care provider immediately. 

How soon will test results be 

available? 

Results for simple tests such as cystometry 

and uroflowmetry are often available immediately after the test. Results of other tests 

such as electromyography and video urodynamic tests may take a few days to come 

back. A health care provider will talk with 

the patient about the results and possible 

treatments. 

Points to Remember 

• The urinary tract is the body’s drainage 

system for removing wastes and extra 

water. 

• The lower urinary tract includes the
 

bladder and urethra.
 

• Urodynamic testing is any procedure 

that looks at how well the bladder, 

sphincters, and urethra are storing and 

releasing urine. 

• Most urodynamic tests focus on the 

bladder’s ability to hold urine and empty 

steadily and completely. 

• Urodynamic tests include uroflowmetry, postvoid residual measurement, 

cystometric test, leak point pressure 

measurement, pressure flow study, electromyography, and video urodynamic 

tests. 

• Most urodynamic tests do not involve 

special preparations. Depending on 

the test, a person may be instructed to 

arrive for testing with a full bladder. 

• After having urodynamic tests, a person 

may feel mild discomfort for a few hours 

when urinating. 

• Results for simple tests are often available immediately after the test, while 

other test results may take a few days to 

come back. 

Hope through Research 

In recent years, researchers have learned 

much about the causes and treatment of 

lower urinary tract problems. Researchers 

are looking into ways to more accurately 

assess LUTS and diagnose lower urinary 

tract problems. Research focuses on designing and developing more accurate and reliable diagnostic tests and tools. 

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) 

sponsors studies of diagnostic urodynamic 

methods and devices. The NIDDK also 

sponsors programs aimed at understanding, diagnosing, and treating lower urinary 

tract problems. NIDDK-funded studies 

have shown associations between LUTS 

and nonurologic diseases and conditions. 

These findings have important diagnostic 

and management implications. Continued 

improvement in urodynamic testing will help 

support advancements in understanding 

these associations. 

5  Urodynamic Testing 
Participants in clinical trials can play a more 

active role in their own health care, gain 

access to new research treatments before 

they are widely available, and help others 

by contributing to medical research. For 

information about current studies, visit 

www.ClinicalTrials.gov. 

For More Information 

American Urological Association Foundation 

1000 Corporate Boulevard 

Linthicum, MD 21090 

Phone: 1–800–828–7866 or 410–689–3700

Fax: 410–689–3998 

Email: auafoundation@auafoundation.org 

Internet: www.auafoundation.org 

www.UrologyHealth.org 

Interstitial Cystitis Association 

100 Park Avenue, Suite 108–A 

Rockville, MD 20850 

Phone: 1–800–HELP–ICA (1–800–435–7422) 

or 301–610–5300 

Email: icamail@ichelp.org 

Internet: www.ichelp.org 

Acknowledgments 

Publications produced by the Clearinghouse 

are carefully reviewed by both NIDDK scientists and outside experts. This publication 

was originally reviewed by Michael Albo, 

M.D., University of California, San Diego, 

Medical School, and Holly E. Richter, Ph.D., 

M.D., University of Alabama at Birmingham 

School of Medicine. 

You may also find additional information about this 

topic by visiting MedlinePlus at www.medlineplus.gov. 

This publication may contain information about 

medications. When prepared, this publication 

included the most current information available. 

For updates or for questions about any medications, 

contact the U.S. Food and Drug Administration tollfree at 1–888–INFO–FDA (1–888–463–6332) or visit 

www.fda.gov. Consult your health care provider for 

more information. 

National Kidney and 

Urologic Diseases 

Information Clearinghouse 

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Phone: 1–800–891–5390 

TTY: 1–866–569–1162 

Fax: 703–738–4929 

Email: nkudic@info.niddk.nih.gov 

Internet: www.urologic.niddk.nih.gov 

The National Kidney and Urologic Diseases 

Information Clearinghouse (NKUDIC) 

is a service of the National Institute of 

Diabetes and Digestive and Kidney Diseases 

(NIDDK). The NIDDK is part of the 

National Institutes of Health of the U.S. 

Department of Health and Human Services. 

Established in 1987, the Clearinghouse 

provides information about diseases of the 

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This publication is not copyrighted. The Clearinghouse 

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This publication is available at 

www.urologic.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 12–5106 

January 2012 

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