Innovation for Pelvic Health

Urodynamics testing is used to describe lower urinary tract function, and diagnose functional disorders affecting the bladder, urethra, and pelvic floor. Urologic clinicians play a central role in urodynamics testing; they are primarily responsible for performing more than 75% of evaluations completed in North America. While the value of a well-done urodynamics assessment is well established, comparatively few clinicians have received formal training in the area. This article describes hydrodynamic principles underlying the measurement of intravesical, abdominal and detrusor pressures. This is the first in a series of articles that will review principles of best urodynamics practices.

Uroflowmetry is an electronic recording of urinary flow. It is typically measured by one of two types of transducers. One type measures the weight of urine as it falls into a beaker or container placed on the transducer, and the other uses a spinning disc to measure urinary flow. Uroflowmetry is a non-invasive, comparatively inexpensive study often used to identify voiding abnormalities. Experienced clinicians can use uroflow tracings to differentiate a continuous (normal) flow pattern from abnormal patterns. While uroflowmetry has been found to reliably distinguish normal from abnormal flow patterns, uroflowmetry does not reliably distinguish the underlying cause of voiding abnormalities. Differential diagnosis of poor detrusor contraction strength from bladder outlet obstruction relies on a voiding pressure flow study that combines uroflowmetry with the various pressure studies used to generate a cystometrogram and pelvic floor muscle electromyography.

Electromyography (EMG) of the pelvic floor muscles is a valuable but challenging component of urodynamics testing. Optimal assessment relies on thoughtful selection of needle, wire, or surface patch electrodes; consistent display of EMG tracings simultaneously with pressure and flow tracings; and minimization of technical and environmental artifacts. This article reviews technical aspects of EMG, including the selection of the best electrodes for a given clinical scenario, minimization of environmental and technical artifacts, and clinical measurement during the filling cystometrogram and voiding pressure flow study.

This article focuses on patient preparation prior to multichannel urodynamics testing and follow-up care related to the testing procedure. Patients may experience anxiety related to urodynamics testing, and individual counseling with patients and the use of educational brochures or online information explaining the study may reduce anxiety. Expert opinion strongly suggests that urodynamics testing should seek to reproduce bothersome lower urinary tract symptoms (LUTS), and therefore, patient preparation for testing often begins with an assessment of LUTS, either volunteered by the patient or elicited by a written or online form. Completion of a form is strongly encouraged to ensure patients are queried about all potentially relevant LUTS. Antimicrobial prophylaxis should not be routinely administered, but suppressive antibiotics may be beneficial in highly selected patients. Medications prescribed to modulate lower urinary tract function may be discontinued, but some patients should be evaluated while taking these medications depending on the goals of testing. Mechanical cleansing of the bowel on the day of testing is rarely indicated, but management of bowel elimination symptoms is routinely indicated because of the association between lower urinary tract and fecal elimination dysfunction. Instructions and counseling following testing will ensure that the patient has an opportunity to discuss findings. Consumption of additional fluids to reduce transient bacteriuria and taking a warm bath or shower are also encouraged to alleviate any residual discomfort.

Lower urinary tract function is characterized by two stages: bladder filling/storage and micturition. Natural bladder filling tends to be slow, intermittent and variable, while urodynamics testing employs a continuous, supraphysiologic fill rate. A clear understanding of the typical proportion between bladder storage and micturition is essential when urodynamics findings are interpreted within a clinical setting. When completing a filling cystometrogram, the urodynamics clinician must answer five essential questions to generate clinical meaningful results: bladder capacity, bladder wall compliance, competence of the urethral sphincter mechanism, sensations of bladder filling, and detrusor response to bladder filling/storage. While the emphasis of each question differs depending on the patient’s lower urinary tract symptoms and specific questions posed by the referring physician, the combined answers to these questions form a comprehensive evaluation of lower urinary tract filling and storage functions. This article will address how the urodynamic clinician answers the first question, “What is the capacity of this bladder?”

This article defines the concept of bladder wall compliance, discusses various means of measuring or assessing compliance, and reviews its clinical relevance. Based on existing evidence, low bladder wall compliance is attributable to increased detrusor muscle tone during bladder filling or changes in the viscoelastic properties of the bladder wall that impede the bladder wall’s ability to stretch. While one can identify the individual components that compromise compliance, the filling CMG is only able to detect whole bladder wall compliance (for example, the combined effects of increased detrusor muscle tone and compromised viscoelastic properties of the bladder wall). From a clinical perspective, whole bladder wall compliance is divided into two categories: normal and low. Low bladder wall compliance is clinically relevant because of its potential to produce upper urinary tract distress, and there is increased risk for febrile urinary tract infections, ureterohydronephrosis, vesicoureteral reflux, renal scarring, compromised urinary tract function, and urinary incontinence because of its direct influence on the bladder outlet. It may produce pain and pressure in the patient with preserved sensations of bladder filling. Low bladder wall compliance is associated with a variety of clinically relevant disorders, including neurogenic bladder dysfunction, pelvic irradiation, interstitial cystitis, and radical prostatectomy.

The ‘Traces” series discusses how the urodynamic clinician generates usable data from a filling cystometrogram. Part 7 focuses on the question, “Is the urethral sphincter mechanism competent?” From a practical viewpoint, this question can be divided into two queries: 1) does this patient have observable urodynamic stress urinary incontinence (SUI) and 2) does this patient have intrinsic urethral sphincter incompetence, also referred to as intrinsic sphincter deficiency or a low pressure urethra? Signs of SUI include clinician observation of urine loss with coughing or during Valsalva’s maneuver. Urodynamic SUI is the observation of urine loss with increased abdominal and intravesical pressures in the absence of a detrusor contraction. The most commonly used techniques for assessment of urethral sphincter function and SUI are the urethral pressure profile and the abdominal leak point pressure. Both are useful for answering these queries, but both tests are vulnerable to physiologic and technical artifacts that must be minimized to produce technically accurate and clinically meaningful results.

The “Traces” series discusses how the urodynamic clinician generates usable data from a filling cystometrogram (CMG). Part 8 focuses on the question, “What are the sensations of bladder filling?” Recent research suggests that sensations of bladder filling wax and wane from consciousness in healthy persons free of bothersome lower urinary tract symptoms. Because of its invasive and atypical nature when compared to daily life, multichannel urodynamics testing cannot reproduce the numerous and complex variables that influence bladder sensation in the healthy individual, making the evaluation of sensations of bladder filling a particularly challenging component of the filling CMG. Routine assessment of bladder sensations focuses on identification of three landmarks – first sensation of bladder filling, first desire to void, and a strong desire to void. A fourth sensation, bladder fullness or a compelling desire to void, is recommended. In addition to assessing these sensations, the urodynamic clinician must assess sensations indicating associated disease or disorders affecting lower urinary tract function, including urgency, pain and atypical sensations. This assessment should be completed in the context of the results of one or more validated instruments used to measure bladder sensations.

It is well known that patients suffer from urinary symptoms and incontinence in positions that differ from the somewhat artificial conditions created by conventional urodynamic studies. This poses a problem in analysis of the data, particularly when we consider that one of the main goals of such studies is to reproduce the patient’s state when experiencing symptoms or abnormal bladder dynamics, allowing the healthcare provider to gain insight into the pathophysiology of the underlying problem and to devise sound treatment options.

The goal of urodynamics testing is to provide objective confi rmation of the signs and symptoms of incontinence and voiding dysfunction. While diagnosis and optimal treatment of lower urinary tract dysfunction require a careful history and objective evaluation, it has been demonstrated that urinary symptoms alone are not specifi c in predicting the type of dysfunction (15%–40% of diagnoses will be wrong without urodynamics testing, and 25%–30% of patients will have multiple diagnoses).