Urodynamic study (UDS VDS)

Urodynamic study/Video-Urodynamic study (UDS/VUDS)

What is a Urodynamic Study (UDS)?

A Urodynamic Study is a real-time functional study of the bladder and the outlet and involves the infusion of saline into the bladder via a small urethral catheter. 

As the bladder fills and then empties, the urologist will be able to assess its storage and voiding patterns to reach a diagnosis of the patient’s issues. The aim of this study is to replicate the patient’s problem so that we can give more specific treatment.

What is a Video-Urodynamic Study (VUDS)?

The function of a VUDS is similar. However, in this case, the bladder is filled with dyed water and X-rays are taken in the process for better visualisation of the urological organs.

What is a Urodynamic Study for?

A urodynamic test helps the urologist assess your bladder’s ability to retain and release urine without stopping. This gives the urologist more information about your urination process and checks if your bladder muscles and sphincters are working well. In short, it allows us to reproduce your urinary symptoms during the study. 

A UDS includes cystometry and uroflowmetry in the same sitting. 

  • Cystometry — This test measures how much urine the bladder can hold, as well as the pressure inside the bladder. It helps your urologist discern how full your bladder is before you have the urge to urinate. 
  • UroflowmetryThis is a test that will measure your voiding function by analysing the speed and volume of your urination. It also helps your urologist discern whether there is any obstruction to the flow of urine.

Often, this test is recommended by your urologist when you experience the following symptoms:

  • Urinary leaking
  • Difficulty holding your urine
  • Frequent urination
  • Difficult urination
  • Difficulty with bladder emptying

We perform these studies to understand your condition better so that the right treatment plan and medical advice can be given to you.

Who is a UDS/VUDS recommended for?

As mentioned earlier, they are usually 


  • Mixed incontinence
  • Overactive bladder (OAB)
  • Failed medical therapy for OAB/BPH
  • Suspected bladder outlet obstruction
  • Neurological conditions with urinary symptoms
  • Neurological conditions with the upper urinary tracts
  • Planning for specific surgeries which require assessment of the bladder or urethra
  • Previous surgery with persistent urinary symptoms
  • Incontinence after surgery (e.g: Transurethral resection of prostate, radical prostatectomy, mid-urethral slings)
  • Voiding dysfunction

How do I prepare for a UDS/VUDS?

Please complete your bladder diary before the study as it contains very useful information for the urologist before the study. Other steps you can take are to:

  • Have your meal before the study.
  • Arrive at least half an hour before the study.
  • Stop taking some medication before the test, as advised by your doctor.
  • Take the oral laxatives prescribed to you 2 days before the test to clear your bowels.
  • Limit your fluid intake and avoid caffeinated drinks 2 hours before your test.

We may need to check in advance with a urine sample that no infection is present.If you have an infection, you should be treated with antibiotics before the urodynamic study can be carried out. Please bring the results of the urinary test to your appointment if it is not done at the hospital.

What can I expect from a UDS/VUDS?

The test takes about 30-60 minutes to complete and will involve small doses of radiation for VUDS.


  1. You will be brought to a quiet room with your nurse and attending urologist.

  2. In a lying position with a local anaesthetic gel (to numb the urethra), a small catheter is inserted in your urethra. Another catheter is placed in your rectum. They will be taped to your body.
    • Both catheters measure the pressure in your bladder and your abdomen with the traces being reflected on the computer screen.
  1. Sensing electrodes may be placed near your rectum and these will monitor the activity of the pelvic muscles.
  2. You may then be asked to stand up or sit down throughout the study. We may ask you to change your position if required.
  3. Using the catheter, your bladder will be filled with a sterile saline fluid and you will be asked to cough or bear down to test your bladder reaction throughout the test.
  4. The doctor checks if there is any leakage of urine and if you have any abnormal urge to urinate.
  5. When your bladder is completely full, you are asked to empty your bladder while pressure is being recorded. This is done with the urethral catheter in your bladder.



  1. The urinary flow will be recorded and you may be asked to do certain actions to assist in the flow.
  • You may be asked to cough, strain or lean forward.
  1. The residual urine volume will be measured.
  2. At the end of the cystometry test, the catheters and sensors are removed.

What to expect after a UDS/VUDS

Right after the tests are done, your doctor will discuss the results with you, and any further treatment you may need. 

You may experience blood in your urine for the next 2 days or discomfort in your urethra. Drink plenty of liquids after the tests to reduce discomfort while urinating.

Are there any risks to UDS/VUDS?

UDS/VUDS is generally a safe and well-tolerated study. Although rare, a risk may be sudden high blood pressure (autonomic dysreflexia), especially in patients with neurological conditions (e.g. spinal cord injury). It is a sudden and exaggerated automatic response to various stimuli in patients with spinal cord injury or spinal dysfunction. 

Sudden high blood pressure can be life-threatening if not properly managed. We will need to closely monitor the blood pressure of these patients during the tests. Please let your urologist know if you have any spinal cord injuries or concerns.   

UTI is also a side effect but is uncommon. 


A urodynamic study is an effective functional study of the bladder and its storage and voiding patterns to understand the patient’s condition better.

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Dr. Fiona Wu 2

Dr Fiona Wu
Consultant Urologist

MBBS (S'pore), MRCS (Edin), MMED (Surg),
MMED (Clinical Investigation),
FRCS (Urol) (RCPSG), FAMS (Urology)

Dr Fiona Wu is an experienced Consultant Urologist and is the Medical Director of Aare Urocare.

Prior to her private practice, Dr Fiona Wu spent 15 years in public service. She was a Consultant in the Department of Urology at National University Hospital (NUH), Alexandra Hospital and Ng Teng Fong General Hospital. She was also the Programme Director of Surgery-in-Training at NUH and a core faculty member of postgraduate junior doctors. 

Dr Wu’s clinical interests lie in Female Urology, Neuro-urology, Urinary Incontinence, Reconstructive Urology and Voiding Dysfunction. She believes in treating incontinence in a holistic way using minimally invasive methods. She worked closely with the gynaecology and colorectal departments to treat complex pelvic floor conditions and continues to do so in her own practice. 

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