Rigi10™ Malleable Penile Prosthesis
Also Known As
Urodynamics, Urodynamic Testing, UDS, Bladder function tests, Cystometrogram (CMG) - (though CMG is a component, sometimes used more broadly)
Definition
Urodynamic studies, often referred to simply as urodynamics, are a series of diagnostic tests that assess the function and dysfunction of the lower urinary tract (LUT), which includes the bladder and urethra.1 These studies measure relevant physiological parameters to evaluate how the bladder stores and releases urine.1 The primary purpose of urodynamic testing is to provide a detailed understanding of bladder and urethral activity, helping clinicians to diagnose the cause of various urinary symptoms such as incontinence, frequent urination, painful urination, problems starting or stopping urination, and issues with bladder emptying.1
How urodynamic studies work involves several components. A multi-channel urodynamic test typically comprises uroflowmetry, cystometry, pressure-flow study, urethral pressure profile, and electromyography.2 Uroflowmetry is a non-invasive test that measures the rate and volume of urine flow.2 Invasive components like cystometry involve inserting a small catheter into the bladder to fill it with sterile water or saline while measuring bladder pressure; another catheter may be placed in the rectum or vagina to measure abdominal pressure.6 This allows for the assessment of bladder sensation, capacity, compliance (how well the bladder can stretch), and the presence of involuntary bladder contractions.1 A pressure-flow study, conducted during voiding, measures the pressure generated by the detrusor muscle (bladder muscle) and the corresponding urine flow rate, which helps differentiate between impaired bladder contractility and bladder outlet obstruction.7 Urethral pressure profilometry measures urethral competence, and electromyography records pelvic floor muscle activity.2 The overall goal is to replicate the patient’s symptoms during the test to correlate them with objective urodynamic findings, leading to an accurate diagnosis and guiding treatment decisions.
Clinical Context
Urodynamic studies are utilized clinically in a variety of situations to diagnose and manage lower urinary tract symptoms (LUTS). They are particularly valuable when the diagnosis is unclear, when empirical treatments have failed, or before invasive surgical interventions are considered.15 The studies help in identifying specific LUT dysfunction, such as detrusor overactivity (DO), bladder outlet obstruction (BOO), detrusor underactivity (DU), stress urinary incontinence (SUI), and impaired bladder compliance.14
Relevant medical conditions where urodynamics are often indicated include neurogenic bladder (e.g., due to spinal cord injury, multiple sclerosis, Parkinson’s disease), complex or recurrent urinary incontinence, voiding dysfunction in men (often to differentiate BOO from DU, especially before prostate surgery), and in women with LUTS where initial assessment is inconclusive.14 For instance, in women, urodynamics can help differentiate types of incontinence (stress, urge, mixed) and assess for conditions like DO or SUI.22 In men, particularly those with LUTS potentially due to benign prostatic hyperplasia (BPH), urodynamics can confirm BOO and assess detrusor function, which is crucial for predicting surgical outcomes.64
Patient selection criteria for urodynamic studies generally include individuals with persistent LUTS despite conservative management, those with suspected neurological causes for their bladder dysfunction, patients with previous pelvic surgery who develop new LUTS, or when the findings might significantly alter the management plan.14 For example, the American Urological Association (AUA) and Society for Urodynamics, Female Pelvic Medicine, and Urogenital Reconstruction (SUFU) provide guidelines on indications, which include identifying LUT dysfunction, predicting consequences on the upper urinary tract, predicting management outcomes, assessing intervention outcomes, and evaluating treatment failure.14
While urodynamic studies are primarily diagnostic rather than surgical procedures themselves, they play a critical role in guiding surgical decisions. For example, confirming detrusor overactivity might lead to medical management or neuromodulation rather than surgery for SUI, or identifying impaired detrusor contractility might temper expectations from BOO surgery.64 The procedures involve several steps: uroflowmetry (non-invasive urine flow measurement), followed by invasive cystometry (filling the bladder with sterile fluid via a catheter to measure pressure and assess sensation, capacity, and compliance), and a pressure-flow study (measuring bladder pressure and flow during voiding).2 Electromyography (EMG) may be used to assess pelvic floor muscle activity.2
Expected outcomes from urodynamic studies are a detailed physiological assessment of LUT function, leading to a specific urodynamic diagnosis (e.g., detrusor overactivity with incontinence, bladder outlet obstruction with normal detrusor function). This diagnosis helps in tailoring treatment, predicting treatment success, and managing patient expectations.16 For example, women undergoing urodynamic testing are more likely to have a change made to their management compared to those who do not undergo testing.63 Similarly, in men, urodynamics can distinguish BOO from DU, guiding appropriate interventions and improving outcomes for those with proven BOO.64 The studies also help identify patients at risk of upper urinary tract damage due to high bladder pressures, guiding more aggressive management if needed.