Complex urodynamic study

What is a Complex Urodynamic Study (UDS)?

Complex urodynamic study (UDS), also known as multichannel urodynamics, is a modern diagnostic method that provides a detailed assessment of the function of the lower urinary tract — the bladder and the urethra. Unlike ultrasound, MRI, or CT scans, which show the structure of organs, urodynamics evaluates their function: the ability to store and hold urine, and then to empty completely and in a coordinated manner.

The procedure consists of a series of sequential measurements, each providing information about different aspects of bladder and urethral function. Urodynamic testing is performed using specialized equipment that simultaneously records pressure, volume, and urine flow rate.

When is a Urodynamic Study Recommended?

Urodynamic testing is recommended for the following conditions:

Urinary incontinence — stress (with coughing, sneezing, physical activity), urge (sudden uncontrollable urges), or mixed incontinence
Overactive bladder (OAB) — frequent urination, urinary urgency, nocturia (night-time urination)
Difficulty urinating — weak stream, need to strain, intermittent urination
Neurogenic bladder dysfunction — due to diabetes mellitus, multiple sclerosis, Parkinson’s disease, spinal cord injury
Chronic urinary retention — incomplete bladder emptying (post-void residual volume > 100 ml)
Suspected bladder outlet obstruction (BOO) — narrowing of the urinary tract, prostate enlargement, urethral stricture
Detrusor-sphincter dyssynergia (DSD) — lack of coordination between bladder contraction and sphincter relaxation
Pre-operative evaluation — before surgical treatment for incontinence or pelvic organ prolapse
Previous treatment failure — when standard therapy has not produced the expected results

What Does a Urodynamic Study Include?

A comprehensive urodynamic evaluation consists of several stages performed sequentially during a single session. Depending on the clinical situation, your doctor may recommend a full study or specific components.

1. Uroflowmetry

Uroflowmetry is a simple screening test that measures the speed and volume of urination. The patient urinates into a specialized device — a uroflowmeter — which records the flow pattern (flow curve). The test can detect:

Reduced maximum flow rate (a sign of obstruction or detrusor weakness)
Intermittent voiding pattern (may indicate dyssynergia or abdominal straining)
Prolonged voiding time
Voided volume and post-void residual volume (measured by ultrasound or catheterization after voiding)

Uroflowmetry is often the first step in urodynamic testing and is performed before catheter placement.

2. Filling Cystometry (Cystotonometry)

Filling cystometry measures bladder pressure during the filling phase. A thin urethral catheter (7–8 Fr, approximately 2.3 mm in diameter) is placed into the bladder, which is then slowly filled with sterile saline solution at a rate of 20–50 ml/min. A second thin catheter is placed in the rectum (in men) or vagina (in women) to measure intra-abdominal pressure. This allows the calculation of the true pressure generated by the bladder muscle — the detrusor pressure.

During filling cystometry, the following parameters are assessed:

First sensation of filling — the volume at which the patient first feels the bladder filling
First desire to void — the volume at which the urge to urinate first appears
Maximum cystometric capacity — the volume at which the patient can no longer delay voiding (normal range: 400–600 ml)
Bladder compliance — the ability of the bladder wall to stretch during filling; reduced compliance indicates a stiff bladder wall (may be seen in interstitial cystitis, tuberculosis, radiation cystitis)
Detrusor overactivity (DO) — involuntary pressure increases that the patient cannot consciously control; this is the primary urodynamic finding in overactive bladder syndrome

During the study, the doctor will ask about your sensations throughout the filling process. Correlation between subjective sensations and objective pressure measurements is diagnostically important.

3. Pressure-Flow Study (Voiding Cystometry)

This stage is performed immediately after filling cystometry, when the bladder has been filled to maximum cystometric capacity. You will be asked to urinate into the uroflowmeter while the catheters remain in place. The equipment simultaneously records three key parameters:

Detrusor pressure (Pdet) — the strength of bladder contraction, calculated as the difference between intravesical and intra-abdominal pressure
Urine flow rate (Q) — the speed and volume of urination
Electromyographic activity (EMG) — activity of the sphincters and pelvic floor muscles (if EMG electrodes are used)

The correlation between detrusor pressure and urine flow rate enables your doctor to:

Differentiate obstruction from detrusor weakness — high pressure + low flow = obstruction; low pressure + low flow = detrusor underactivity
Assess bladder contractility — using the Abrams-Griffiths nomogram (AG number) or the Bladder Contractility Index (BCI)
Classify the type of obstruction — using the ICS nomogram

The pressure-flow study is the gold standard for diagnosing bladder outlet obstruction in men and for the differential diagnosis of voiding difficulties.

4. Urethral Pressure Profilometry (UPP)

Urethral pressure profilometry measures pressure along the entire length of the urethra. The test is performed using a specialized catheter with a pressure sensor that is slowly withdrawn (automatically or manually) from the bladder through the urethra at a rate of 0.5–1 mm/s. The result is a graph called the urethral pressure profile.

Urethral pressure profilometry evaluates:

Maximum urethral closure pressure (MUCP) — the highest pressure recorded in the urethra (normal: 60–90 cm H₂O in women, higher in men)
Functional urethral length — the segment of the urethra where pressure exceeds intravesical pressure
Area of maximum pressure — the location of the external urethral sphincter
Stress profile — urethral pressure during coughing and straining, used to identify urethral sphincter deficiency — a common cause of stress urinary incontinence

This test is particularly important for diagnosing stress urinary incontinence, planning surgical correction, and evaluating suspected urethral hypomobility.

5. Electromyography (when indicated)

Electromyography (EMG) records the electrical activity of the external urethral sphincter and pelvic floor muscles. The test may be performed using surface electrodes (placed on the perineal skin) or concentric needle electrodes (inserted directly into the sphincter muscle under digital guidance — more precise but invasive).

EMG helps identify:

Detrusor-sphincter dyssynergia (DSD) — involuntary sphincter contraction during voiding
Impaired voluntary sphincter control
Denervation changes in neurogenic disorders

How to Prepare

For the most accurate results, please follow these recommendations:

1–2 hours before the test: drink 500–1000 ml of still water (no caffeine!) to ensure your bladder is naturally filled. Arrive with a comfortably full bladder
The day before: avoid alcohol and caffeinated beverages (coffee, strong tea, energy drinks) as they may affect bladder function
If you take anticoagulants (warfarin, rivaroxaban, apixaban, clopidogrel, etc.) — please inform your doctor. Temporary discontinuation may be necessary
If prescribed — your doctor may recommend a prophylactic dose of antibiotics
Before the procedure: empty your bowels if possible
Bring with you: your referral, previous test results (ultrasound, urine analysis, bladder diary if you have kept one)

How Is the Test Performed?

The procedure is performed on an outpatient basis — no hospitalization is required. You will lie in a urological examination chair (a gynecological chair for women).

Uroflowmetry (if performed as part of UDS): you will urinate into a uroflowmeter — a specialized device resembling a funnel connected to a measuring instrument
Catheter placement: the doctor inserts a thin urethral catheter into the bladder and a thin rectal catheter (in men) or vaginal catheter (in women) for measuring intra-abdominal pressure. This feels similar to routine bladder catheterization
Bladder filling: through the urethral catheter, the bladder is slowly filled with sterile saline solution. The doctor will ask about your sensations throughout the filling. Please answer honestly and do not hold longer than you normally would
Voiding: when the bladder is full, you will be asked to urinate naturally into the uroflowmeter. The catheters remain in place during voiding. Despite some awkwardness, try to urinate as you normally would — this is essential for accurate results
Urethral pressure profilometry: if indicated, this is performed after the main stages
Completion: the catheters are removed, and you can immediately return to your normal activities

The entire procedure takes approximately 30–60 minutes. Results are interpreted by the doctor immediately after the study.

What Will I Feel During the Procedure?

Urodynamic testing is not painful but may cause some discomfort:

Catheter insertion: brief burning or mild discomfort (similar to routine catheterization)
Bladder filling: a gradually increasing sensation of fullness and urge to urinate (a normal sensation, similar to natural bladder filling)
Voiding with catheters: an unusual sensation, but there should be no sharp pain

Remember: the more relaxed you are, the more accurate the results will be. The doctor and staff will do everything to make the procedure as comfortable as possible.

Risks and Possible Complications

Urodynamic testing is a minimally invasive procedure with a low risk of complications. However, the following may occur:

Urinary tract infection (most common, frequency ~2–5%). Symptoms include burning during urination, increased frequency, lower abdominal discomfort. Drinking plenty of fluids after the procedure helps reduce the risk
Microhematuria — a small amount of blood in the urine, usually resolving spontaneously within 24–48 hours
Temporary urinary retention — a rare complication that may require short-term catheterization
Allergic reaction to the local anesthetic (lidocaine) used during catheter placement

Contact your doctor if you experience fever, chills, severe back pain, or blood in the urine for more than 2 days after the procedure.

Understanding Your Results

Urodynamic results enable your urologist to:

Make an accurate diagnosis — distinguish stress from urge incontinence, determine the type of bladder overactivity (motor vs. sensory)
Identify the underlying cause of your symptoms — obstruction, detrusor underactivity, dyssynergia, or a combination
Choose the most appropriate treatment — conservative (behavioral therapy, bladder training, physiotherapy), medical (anticholinergics, beta-3 agonists), or surgical (slings, TURP, sacral neuromodulation)
Predict treatment outcomes — assess the likely effectiveness of planned interventions
Monitor progress — repeat studies can evaluate the effectiveness of treatment over time

It is important to understand that urodynamic testing is only one part of the diagnostic process. Results are always interpreted together with your symptoms, medical history, bladder diary, ultrasound findings, and laboratory tests.

Why Choose Our Center?

State-of-the-art urodynamic equipment meeting international ICS standards
Experienced urologists with specialized training in urodynamic testing
Individualized testing protocol — the study is tailored to your specific symptoms and clinical needs
Comfortable, private setting — your comfort and dignity are our priority