Uroflowmetry and Urodynamic study
Urodynamic testing is the most accurate way to assess the physiological aspects of bladder outlet obstruction. With the increasing use of prostate artery embolization for benign prostatic obstruction, it’s important for interventional radiologists to be familiar with urodynamic assessments and reports to choose appropriate patients. This review outlines the role of urodynamic studies in managing benign prostatic obstruction, including selecting patients, interpreting urodynamic findings, and their potential to predict patient outcomes.
Aim of Uroflowmetry:
| Aim | Description |
|---|---|
| Reproduce the patient’s symptoms during urodynamic testing | Obtain objective information to make an accurate diagnosis of the primary cause of LUTS |
| Distinguish BPO from other causes of LUTS | Differentiate between Bladder Outlet Obstruction (BPO) and other potential causes of Lower Urinary Tract Symptoms |
| Evaluate bladder storage and emptying | Assess how bladder function affects treatment success or complications |
| Determine if serious or irreversible damage has occurred or is at risk | Identify if there is any significant or irreversible damage to the upper and lower urinary tract |
Uroflowmetry Variables and Definations:
| Variable | Definition |
|---|---|
| Cystometry Variables and Definitions during Filling Cystometry | |
| Cystometric capacity | Bladder volume at the end of filling when the patient is allowed to void. Decreased capacities can cause urinary frequency. |
| Bladder compliance | The relationship between the change in bladder volume and change in detrusor pressure. Impaired compliance can lead to increased detrusor pressure during bladder filling, potentially causing incontinence. |
| Detrusor overactivity | Involuntary detrusor contraction during the filling phase, often accompanied by a sense of urgency. |
| Detrusor leak point pressure | Lowest detrusor pressure at which urine leakage occurs in the absence of a detrusor contraction or increased abdominal pressure. |
| Variables Characterizing Pressure-Flow Relationship in Voiding Phase | |
| Maximum pressure | The highest pressure achieved at any time point during the attempt to void. |
| Pressure at maximum flow | The pressure recorded at the time point of maximum flow. |
| Maximum detrusor pressure | The highest pressure within the detrusor muscle during voiding. |
| Pressure-flow study findings | Evaluates the relationship between the pressure generated in the bladder and the urine flow rate, helping to identify obstruction or detrusor underactivity. |
Urodynamic Parameters for Patient Selection:
| Parameter | Consideration for Patient Selection |
|---|---|
| Detrusor pressure at Qmax | High detrusor pressure may indicate potential benefits from interventions like PAE. |
| Bladder compliance | Impaired compliance may affect treatment outcomes; counseling about potential results is crucial. |
| Presence of Detrusor Overactivity | Should be assessed to understand its impact on treatment outcomes. |
| Cystometric capacity | Low capacity may lead to urinary frequency; intervention may be considered. |
| Pressure-flow study findings (BOO or detrusor activity) | These findings help differentiate obstructive vs. contractile origins of LUTS. |
Summary of Important Values in Urodynamic Studies:
| Parameter | Value |
|---|---|
| PVR volume for diagnosing chronic urinary retention | ≥ 300 mL |
| Detrusor pressure at Qmax | < 40 cm H2O (no improvement in symptom score after TURP) Higher pressure - more symptom improvement patients had after treatment |
| Detrusor leak point pressure | > 40 cm H2O indicates high risk for future upper tract deterioration resulting from high storage pressures |
| BOOI (Bladder Outlet Obstruction Index) ICS nomogram | > 40 indicates obstruction |
| Schafer nomogram | Zones 3–6 defines obstruction |
| Qmax for identifying BOO | < 15 mL/s indicates potential BOO |
| Qmax indicating high likelihood of BOO | < 10 mL/s |