Written by Mr Jai Seth, BSc(Hons) MBBS MRCS MSc(Urol) MD(Res) FRCS(Urol)
Consultant Urological Surgeon · Last updated:
Rather than relying on symptoms alone, urodynamics directly records bladder pressures, urine flow, and what happens at the moment of leakage or obstruction. The numbers it produces let a urologist decide which treatment is most likely to help, and which would be wrong for your particular pattern.
When is this test used?
- Bladder leakage that doesn't fit a clear pattern of stress or urge incontinence.
- Symptoms that have persisted despite first-line treatment: bladder training, pelvic floor exercises, or oral medication.
- Mixed urinary symptoms in men where it is not clear whether the bladder, the prostate, or both are responsible.
- A weak urinary stream or difficulty emptying the bladder, where the cause has not been established.
- Suspected detrusor overactivity (an overactive bladder muscle) before deciding on bladder Botox, percutaneous tibial nerve stimulation, or sacral neuromodulation.
- Neurological conditions affecting bladder function: multiple sclerosis, spinal cord injury, Parkinson's disease.
- Before surgery for stress incontinence (sling, colposuspension, urethral bulking) or for prostate enlargement (HoLEP, TURP, UroLift), to confirm the bladder is contributing to symptoms in the expected way.
- Bladder pain or recurrent urinary tract infections where flow and emptying need to be characterised.
Before the test
- A bladder diary for two to three days before the test is usually requested. The diary records each drink, each visit to the toilet, and any leakage, and gives the urodynamic recording context to interpret.
- No special diet or fasting is required. You can eat and drink normally on the day of the test.
- Medication review. If you take tablets for bladder symptoms (antimuscarinics such as solifenacin or oxybutynin, or mirabegron), you are usually asked to stop them a week before the test (BAUS patient leaflet, 2025) so that your bladder behaves as it would untreated. Prostate medicines (alpha-blockers, finasteride or dutasteride) are reviewed individually. Do not stop any medication without checking, particularly for prostate enlargement, where an alpha-blocker may be the only treatment between symptoms and acute retention.
- A urine sample is dipstick-tested on the day; if it shows infection, the test is usually postponed for a week or two and antibiotics given first (BAUS). Antibiotics are also sometimes given around the test if you have a history of urinary tract infection, because a small catheter is inserted into the bladder during the procedure.
- Arrive with a comfortably full bladder if asked. The test usually begins with a free flow recording, and a moderately full bladder gives a clearer reading.
During the test
- Uroflowmetry (free flow). You pass urine, in private, into a specialised toilet that measures the strength and pattern of the stream. This takes the time it would normally take you to pass urine, a couple of minutes.
- Bladder scan. A small ultrasound check confirms how much urine, if any, is left in the bladder after you pass urine.
- Cystometry (filling and storage). A thin catheter is passed through the urethra into the bladder. A second, even thinner catheter is placed in the rectum (or, less commonly, the vagina). This measures abdominal pressure. The bladder is then slowly filled with warm sterile fluid while pressures are recorded. During this phase, you will be asked to report sensations: when you first feel the bladder filling, when the urge to pass urine appears, when you feel you could no longer hold on. You may also be asked to cough, change position, or step from the chair, so that the test captures what happens during normal daily provocation.
- Pressure-flow study (voiding). When the bladder is full and you cannot defer longer, you pass urine while the catheters are still in place. The recording shows whether the detrusor (bladder muscle) is generating adequate pressure, and whether the bladder is emptying against any obstruction.
- Video-urodynamics, when indicated. A small amount of contrast in the filling fluid allows real-time X-ray imaging during the test. This shows whether urine moves back up to the kidneys (vesicoureteric reflux), whether the bladder neck opens normally during voiding, and whether the urethra leaks during effort.
- The whole sequence usually takes 45 to 60 minutes. You remain dressed from the waist up throughout; a sheet covers your legs during the catheter phases. A specialist nurse is present.
After the test
- Most people go home within 15 to 30 minutes of the test ending.
- Mild stinging when passing urine for the first 24 hours, in between 1 in 2 and 1 in 10 people (BAUS patient leaflet, 2025). Drinking plenty of fluid usually settles it.
- A small amount of blood in the urine, also in between 1 in 2 and 1 in 10, which is not a cause for concern unless it persists or is heavy.
- A urinary tract infection needing antibiotics, in between 1 in 10 and 1 in 50 (BAUS). Antibiotics are given straight away if symptoms develop: burning, fever, cloudy urine. People at higher risk of infection are given antibiotics after the test as a precaution.
- Less often, the catheter cannot be passed and the test is abandoned for another day or route (between 1 in 10 and 1 in 50). Temporary retention needing a catheter, and a test that does not find the cause and may need repeating, each occur in between 1 in 50 and 1 in 250 (BAUS).
- Urodynamic traces are reviewed by the consultant who ordered the test, usually within a few days. You will be invited back to discuss what the test showed and what it means for your treatment options.
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