INTRODUCTION — Urodynamics refers to a group of tests used to assess function of the urinary tract by measuring various aspects of urine storage and evacuation (table 1). Some specific types of urodynamic testing are:
●Cystometry (or cystometrogram) evaluates bladder function by measuring pressure and volume of fluid in the bladder during filling, storage, and voiding.
●Uroflowmetry measures the rate of urine flow.
●Urethral pressure profile tests urethral function.
●Leak point pressure determines the bladder or abdominal pressure when leakage occurs due to increased abdominal pressure (Valsalva or cough) to assess urethral resistance.
The purpose of urodynamic testing is to aid in understanding physiologic mechanisms of lower urinary tract dysfunction, thereby improving the accuracy of diagnosis and facilitating targeted treatment.
The procedure and interpretation of results of urodynamic testing in women is reviewed here. The preoperative evaluation of women stress urinary incontinence is discussed separately. (See "Surgical management of stress urinary incontinence in females: Preoperative evaluation for a primary procedure".)
In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transgender and gender-expansive individuals.
EFFICACY — Clinical evaluation with urodynamics may lead to a more accurate diagnosis of incontinence type [1-6]. A meta-analysis including several thousand women reported the symptom of stress incontinence, when compared against a urodynamic diagnosis, was 91 percent sensitive, but only 51 percent specific in diagnosing pure stress incontinence . For urgency incontinence, history alone was 73 percent sensitive, but only 55 percent specific.
In a chart review study of women with urinary incontinence, the probability of a change in treatment plan with, versus without, urodynamic data was 27 percent . A prospective study of the impact of urodynamics on treatment and outcomes in women with overactive bladder reported that women who received treatment concordant with their urodynamic findings were more likely to report an improvement in bladder symptoms . Another study reported the preoperative urodynamic testing in women with urinary incontinence and pelvic organ prolapse prompted changes to the treatment plan in 44 percent of patients .
By contrast, a Cochrane review concluded there were insufficient data from randomized studies to determine whether treatment of urinary incontinence according to a urodynamic-based diagnosis was more effective than treatment based upon history and examination alone .
Numerous pitfalls in urodynamic testing limit its value . Some fundamental problems include:
●Lack of standardization of technical details, such as patient position, type of pressure sensor, and filling rate. These variables significantly affect results.
●The artificial situation of the urodynamic laboratory can produce nonphysiologic results in some patients due to anxiety, embarrassment, and/or pain. Differing trials have attempted to assess the impact of dimmed lights, music, and educational videos on improving patient comfort; results are mixed [9,12].
●Use of a transurethral catheter can unmask stress incontinence .
●Inconsistent reproducibility of test results in the same patient .
●The wide range of physiologic values in normal, asymptomatic patients .
●The absence of a specific abnormality during urodynamic testing does not exclude its existence, and not all abnormalities found during urodynamics are clinically significant.
Thus, a urodynamic test cannot be considered definitive without placing it in the context of other findings. A complete patient evaluation should consist of:
●Measurement of postvoid residual urine volume.
●Urinary diary (a record of volume and frequency of fluid intake and voiding over one to seven days).
INDICATIONS — Urodynamic evaluation is useful mainly in women with complicated stress urinary incontinence or mixed incontinence. Urodynamic testing may also help clarify the mechanisms of overflow incontinence. Urge incontinence seldom requires urodynamic testing except in cases where the patient does not respond to conservative management.
The indications for preoperative urodynamic testing in women with stress urinary incontinence are discussed in detail separately. (See "Surgical management of stress urinary incontinence in females: Preoperative evaluation for a primary procedure", section on 'Urodynamic testing'.)
COMPLICATIONS — Bacteriuria has been reported in 3 to 8 percent of women after urodynamic testing but is usually transient [16,17]. Prophylactic antibiotics are usually not necessary [18,19]. However, an expert panel recommended a single oral dose of trimethoprim-sulfamethoxazole before urodynamic evaluation (with alternative antibiotics in case of allergy or intolerance) for women with neurogenic lower urinary tract dysfunction, elevated postvoid residual, asymptomatic bacteriuria, immunosuppression, age over 70, and patients with indwelling catheter or performing intermittent catheterization .
CYSTOMETRY — Filling cystometry is the method by which the pressure/volume relationship of the bladder is measured during bladder filling. It is used to assess detrusor activity and bladder sensation, capacity, and compliance. Cystometry can be done with one channel measuring bladder pressure alone or with an additional channel that simultaneously measures abdominal pressure through the rectum or vagina. The advantage of the multichannel test is that it can discriminate between changes in abdominal versus bladder pressure by electronically subtracting the abdominal component from intravesical pressure.
Only a multichannel test can show that a rise in bladder pressure is due to detrusor contraction rather than tensing of the abdominal wall. This information is important for avoiding a false impression of detrusor overactivity. As an example, detrusor overactivity during single channel cystometry is not reproducible by multichannel testing in 40 percent of women . Thus, most, but not all , experts believe that the multichannel test result is the most reliable for evaluating women with incontinence.
Some urodynamic machines can also record urethral pressure with a second sensor on the bladder catheter (see below). This allows electronic calculation of urethral closure pressure, which is the difference between urethral and bladder pressures. Leakage usually occurs when bladder pressure exceeds urethral pressure. However, the clinical value of this measurement has not been proven.
Indications — The most common reason to do cystometry is to distinguish detrusor overactivity (involuntary contractions of the bladder) from stress incontinence (leakage due to an increase in abdominal pressure) (figure 1). The test can also identify patients with abnormalities of bladder sensation and mixed incontinence.
In patients with pelvic organ prolapse, preoperative urodynamic evaluation can identify patients with hidden incontinence (also called occult incontinence). This is defined as stress incontinence which occurs when the bladder is filled, elevated with large cotton swabs or a pessary, and then asked to cough or perform Valsalva. (See "Pelvic organ prolapse and stress urinary incontinence in females: Surgical treatment", section on 'Occult SUI'.)
Although this test does not identify all patients with hidden incontinence, a positive test would indicate that a stress incontinence procedure should be done as part of the prolapse operation. Those patients with a negative test can be counseled that they still could develop stress incontinence and could require a second surgical procedure .
Data — The International Continence Society (ICS)  defines cystometry data points as the volume at which the patient notes:
●First desire to void – The patient would like to pass urine at the next convenient moment, but voiding can be delayed if necessary.
●Strong desire to void – A persistent desire to void, but without fear of leakage.
●Urgency – A sudden compelling desire to void.
●Maximum cystometric capacity – The patient feels she can no longer delay micturition.
●Increased bladder sensation – An early first sensation of bladder filling (or an early desire to void) and/or an early strong desire to void, which occurs at low bladder volume and which persists.
●Reduced bladder sensation – Diminished sensation throughout bladder filling.
●Absent bladder sensation – The individual has no bladder sensation.
●Nonspecific bladder sensations – May make the individual aware of bladder filling, for example, abdominal fullness.
Other information includes:
●Compliance (the change in volume divided by change in detrusor pressure).
●Overactive bladder (any contractions, spontaneous or provoked, are abnormal during filling).
Normal voiding function — Effective voiding requires intact bladder sensation, a contractile detrusor muscle, and a nonobstructed bladder outlet (figure 2). As the bladder fills, active relaxation results in a low-pressure, high-compliance bladder. The normal bladder should not have involuntary phasic contractions during filling despite provocation. It should initially expand without resistance or increased intraluminal pressure. The urethral sphincter should relax and open when the patient wants to initiate voiding, accompanied by detrusor contractions. During voiding, detrusor contraction should be smooth and lead to a steady urine stream.
There are no recognized standards for normal values. However, a reasonable range for first desire to void is 100 to 200 cc, normal desire to void 150 to 350 cc, urgency 250 to 500 cc, and maximum cystometric capacity 300 to 600 cc. A small rise in detrusor pressure (ie, less than 10 to 15 cm of water) without undue sensation of urgency up to a capacity of 400 to 500 is also normal. Values outside these ranges do not necessarily indicate pathology, but could confirm a problem in symptomatic patients. Test results must correlate with symptoms to be meaningful.
Common abnormalities — Some of the more common bladder abnormalities and their cystometric findings are described below:
Detrusor overactivity — Detrusor overactivity (overactive bladder) can be diagnosed if there is urgency or leakage with a detrusor contraction that the patient cannot suppress. The involuntary detrusor contractions during the filling phase may be spontaneous or provoked by maneuvers such as posture change from prone to standing, toe raises, running water, or hand washing. In women with neurologic disease, uninhibited detrusor contractions are termed neurogenic detrusor overactivity. When there is no defined cause, detrusor overactivity is labeled as "idiopathic."
●Phasic detrusor overactivity – A characteristic wave form which may or may not lead to urinary incontinence.
●Terminal detrusor overactivity – A single, involuntary detrusor contraction, occurring at cystometric capacity, which cannot be suppressed and results in incontinence usually with bladder emptying (voiding).
●Detrusor overactivity incontinence – Incontinence due to an involuntary detrusor contraction.
Abnormalities of bladder sensation include the following:
●Increased bladder sensation – The individual feels an early and persistent desire to void.
●Reduced bladder sensation – The individual is aware of bladder filling, but does not feel a definite desire to void.
●Absent bladder sensation – The individual reports no sensation of bladder filling or desire to void.
Stress urinary incontinence — Stress urinary incontinence is characterized by leakage that occurs with an increase in abdominal pressure, such as coughing or Valsalva, without a rise in true detrusor pressure.
Idiopathic sensory urgency — Idiopathic sensory urgency should be considered in women with sensory parameters below the normal range. Symptoms include urgency at a low bladder volume, low bladder capacity, and frequency. However, patients with stress and urgency incontinence also often have low sensory volumes because they adapt to the risk of leakage by emptying the bladder frequently. These latter disorders can be excluded by absence of the findings described above.
Neurologic abnormality — Neurologic abnormality is suggested by an above normal capacity and high volume at first desire. A hypotonic bladder fails to empty adequately due to inadequate detrusor pressure. Flow rate is usually low.
Interstitial cystitis — Interstitial cystitis is characterized by low volume at normal desire, low volume urgency, and low capacity in addition to bladder pain. Some patients also have poor compliance. Normal compliance allows bladder filling to occur up to maximum capacity with minimal (5 to 10 cm H2O) change in intravesical pressure.
Elevated baseline pressure — A retrospective study of patients who had midurethral slings for stress incontinence reported that 56 percent of women with a detrusor pressure >15 cm during the filling phase of cystometry developed de novo urgency incontinence after surgery .
Technique — The optimal technique for performing cystometry has not been determined; thus, methods vary among centers. There is no preprocedure preparation. In general, having the patient in a sitting or standing position is more desirable than lying prone because these positions simulate stresses on the bladder that typically occur in daily life. Standing or sitting positions increased the detection of detrusor overactivity in most studies by 33 to 100 percent, according to a systematic review .
The patient begins by emptying her bladder as much as possible. After sterile preparation of the periurethral area with iodine or another antiseptic, a small plastic catheter is slowly inserted into the urethra to measure postvoid bladder volume. After removal of this catheter, a thin urodynamic catheter is inserted until it reaches the bladder. Bladder pressure is continuously measured by the urodynamic catheter. A second catheter is placed either into the rectum or deep in the vagina. This catheter indirectly measures intra-abdominal pressure. The urodynamic machine subtracts intra-abdominal pressure from bladder pressure, which gives a continuous reading of true detrusor pressure (the pressure created by the detrusor muscle alone).
Water or normal saline at room temperature is typically used to fill the bladder, although warm or cold fluid may be useful to provoke detrusor overactivity. Use of carbon dioxide has fallen into disfavor because it is less physiologic, compressible, dissolves in urine to form carbonic acid, and does not permit stress testing or a voiding study.
Most clinicians fill the bladder through the catheter at a rate of 50 to 100 cc/minute. Faster filling rates (greater than 100 cc/minute) are more likely to provoke detrusor overactivity. The woman is asked to describe sensations during filling, including when the first feeling of bladder fullness occurs.
A variety of transducers is available. Water-filled balloon catheters or water perfusion catheters are inexpensive and disposable. Microtransducer catheters are more accurate, but are more expensive, require sterilization, and can produce artifacts depending upon the orientation of the transducer to the bladder or urethral mucosa. A comparison of air-charged and microtransducer catheters in the evaluation of urethral function showed high concordance for maximum urethral closure pressure and valsalva leak point pressure, but not for functional urethral length .
Provocative maneuvers, such as coughing, Valsalva, heel bouncing, jumping, walking in place, change in posture, hand washing, and listening to running water are helpful for determining if they cause leakage and whether the leakage is related to uninhibited detrusor contractions or stress incontinence [28,29].
Once the bladder is completely full, the woman is asked to begin voiding, and measurements are made of pressure, volume, and flow rate.
Postprocedure care — After the procedure, the patient may notice urinary frequency, urgency, hematuria, or dysuria for a day. Increasing fluid intake helps to flush out the bladder, but caffeinated, carbonated, or alcoholic beverages should be avoided because they may irritate the bladder lining. Signs of infection, such as fever, chills, low back pain, or persistent blood in the urine, should be reported to the clinician.
Videourodynamics — This technique is similar to conventional cystometry, but with the addition of a radio-opaque filling medium, video recorder, and x-ray equipment. Videourodynamics may offer information beyond conventional urodynamics in complicated neurologic conditions, but most authorities believe it is seldom indicated . The disadvantages are radiation exposure, cost, and the extra technical support required.
Ambulatory urodynamics — Ambulatory testing can be performed by using commercially available systems in which an ambulatory patient wears an indwelling catheter connected to a microcomputer. The advantage over conventional cystometry is that the home environment reflects the patient's functional status more realistically than the laboratory. Several studies have shown that ambulatory urodynamics are more sensitive than conventional urodynamics in diagnosing detrusor overactivity [31-33]. One study showed that ambulatory monitoring was an effective second-line investigation for diagnosing incontinence in difficult cases .
However, there are several disadvantages to this method. It is costly and artifacts can be produced by catheter movement, leading to difficulty interpreting data and inaccurate diagnoses. As an example, one study found that 69 percent of healthy, asymptomatic women were diagnosed with detrusor overactivity on ambulatory monitoring . At this time, ambulatory urodynamics is useful in research, but not in clinical practice [36,37].
UROFLOWMETRY — Uroflowmetry measures urine volume voided over time. It can be done with or without a pressure-flow study (see below), which measures detrusor pressure during voiding.
Indications — Abnormal voiding is much more common in men than in women. Nevertheless, uroflowmetry is usually done as part of a complete urodynamic evaluation in women. It can be useful in clinical situations, such as:
●Frequency, urgency, and urgency incontinence as some of these patients have outlet obstruction.
●Voiding difficulty, hesitancy, or difficulty maintaining the urine stream, which can also be due to outlet obstruction (from previous pelvic surgery or urethral kinking with anterior vaginal wall prolapse) or weak detrusor (as in neurologic diseases).
●Planned pelvic surgery because poor uroflow may be a predictor of postoperative voiding difficulty after incontinence surgery or radical pelvic surgery. This information allows for preoperative counseling or training in self-catheterization ; however, the predictive value of uroflowmetry is controversial .
Technique — After the physician and nurse have left the room, the patient voids into a special commode that measures the amount and rate of urine flow. Although there are no universally accepted standards, a systematic review of standard uroflow parameters in healthy women (mean age 37) showed the following mean values :
●Voided volume 338 mL
●Maximum flow rate 24 mL/second
●Average flow rate 13 mL/second
●Postvoid residual 16 mL
●Voiding time 29 seconds
In addition, uroflow should occur in a continuous single curve (as opposed to short spikes) of flow.
Flow rates less than 15 mL/second may indicate outlet obstruction, detrusor weakness, or significant Valsalva effort during voiding . An acontractile detrusor is unable to initiate a contraction and will lead to overflow incontinence.
Some patients are unable to void normally in the artificial conditions of the urodynamics laboratory; thus, it is important to ask the patient if she feels that her void was typical for her, especially if an abnormal pattern is observed. If the patient feels the test was atypical, it should be repeated.
PRESSURE-FLOW STUDY — A pressure-flow study measures both bladder pressure and urinary flow. The purpose of a pressure-flow study is to determine the mechanism of abnormal voiding revealed by a low flow rate on uroflowmetry. If the detrusor pressure is high (>50 cm H2O), urethral overactivity (detrusor-sphincter dyssynergia) or urethral obstruction (stricture or tumor) may be present. The most common cause of obstructed voiding in females is prolapse of the anterior vaginal wall, which can cause kinking of the urethra when the bladder descends more than the urethra. In addition, previous pelvic surgery can cause bladder denervation and a weak detrusor muscle. The most common use of the pressure-flow study in women is to determine the cause of voiding dysfunction after surgery .
One study that compared women with bladder outlet obstruction with normal controls reported a maximum detrusor pressure >25 cm H2O gave the greatest sensitivity and specificity, >60 percent for detection of obstruction . A uroflow <12 mL/second gave equal sensitivity, specificity and accuracy (68 percent) for predicting obstruction.
A pressure-flow study can be done as an extension of cystometry when catheters are already in place to measure detrusor and abdominal pressure. The patient voids around the urethral catheter into a commode, which simultaneously measures uroflow.
If the patient has an acontractile or poorly contractile detrusor, she will have a low flow rate (<15 cc/sec maximum flow) and little or no rise in true detrusor pressure. Voiding occurs mainly by abdominal straining. Since many patients use Valsalva to aid voiding, a rise in abdominal pressure alone does not indicate a problem. Detrusor acontractility is often due to a neurologic abnormality, such as spinal cord injury or multiple sclerosis, but it may be idiopathic.
Test results are difficult to assess because of the difficulty of voiding around the catheter, as well as the artificial surroundings of the urodynamics laboratory. There are no accepted standards for the method and interpretation of pressure-flow studies.
URETHRAL PRESSURE PROFILE — The pressure in the urethra should be equal to or greater than the bladder pressure during bladder filling. When the bladder and urethra are in their proper anatomic location, increases in intraabdominal pressure will also increase urethral pressure, thereby preventing leakage. Low urethral pressure can be associated with incontinence and is related to aging, hypoestrogenic state, multiparity, and previous significant urogynecologic operations.
The urethral pressure profile (UPP) measures the intraluminal pressure along the entire length of the urethra with the bladder at rest. A special catheter with an intravesical and an intraurethral pressure transducer and side openings near its tip is perfused and slowly withdrawn from the bladder (figure 1). The transducers are usually brought out to the external urethral meatus at a rate of 1 mm/sec by a mechanical pulling device. The pressure necessary to maintain a constant flow provides an assessment of the activity of the urethral wall.
The clinical purpose of the UPP is to help distinguish intrinsic sphincter deficiency from genuine stress incontinence by measuring:
●Maximum urethral pressure (the highest pressure measured).
●Maximum urethral closure pressure (the difference between maximum urethral pressure and intravesical pressure).
●Functional urethral length (the length where the urethral pressure exceeds the intravesical pressure).
●Pressure-transmission ratio (the increment in urethral pressure on stress as a percentage of the simultaneous increment in vesical pressure) .
The UPP has limited clinical value because of a lack of standardized technique and equipment, as well as variable interpretation . Upright posture and increased bladder volume both increase urethral pressure. The size and stiffness of the catheter and the type of pressure transducer also affect the UPP. When microtransducers are used, pressures vary depending upon the orientation of the transducer, with anterior orientation producing higher pressures and posterior orientation, lower. Therefore, the study is usually done with the transducer in the lateral position.
In addition, detrusor overactivity can affect urethral function resulting in decreases in functional urethral length and pressure transmission ratio with bladder filling . Thus, detrusor overactivity needs to be treated to obtain a valid UPP.
Since the UPP is measuring the urethra at rest, it is of limited value in arriving at a diagnosis in the dynamic situation of incontinence. No single parameter of the UPP is useful in diagnosing stress incontinence . The pressure-transmission ratio also cannot discriminate between stress incontinence patients and controls .
A few studies have indicated that a low maximum urethral closure pressure (usually <20 or <30 cm H2O) is a predictor of poor outcome for retropubic suspension surgery [47-49], and, therefore, some advocate a sling procedure for patients with low urethral closure pressure and urethral hypermobility [50,51]. This reasoning would make the UPP clinically significant. However, there is a strong trend toward sling procedures for all cases of stress incontinence, with or without low urethral pressure, which makes the UPP increasingly irrelevant to choice of surgical procedure . Some experts recommend placing a sling slightly closer to the urethra in patients with low urethral closure pressure or low abdominal leak point pressure, but there are no data to support this recommendation. A retropubic sling is more effective than a transobturator sling for intrinsic sphincter deficiency . (See "Surgical management of stress urinary incontinence in females: Choosing a type of midurethral sling", section on 'SUI background and treatment options'.)
Intrinsic sphincter deficiency without urethral hypermobility is usually treated with periurethral bulking injections (see "Stress urinary incontinence in females: Persistent/recurrent symptoms after surgical treatment"). A UPP with low maximum pressure could provide supportive evidence to justify this method of treatment.
Women younger than 25 have a mean maximum urethral closure pressure of 90 cm H2O, while women older than 64 have a mean of 65 cm H2O . The average functional urethral length declines after menopause. Estrogen increases urethral length and maximum urethral pressure . However, there is no evidence that estrogen decreases incontinence in women with intrinsic sphincter deficiency.
LEAK POINT PRESSURE — Abdominal leak point pressure refers to the intravesical pressure at which urine leakage occurs due to increased abdominal pressure in the absence of a detrusor contraction. The pressure can be produced by Valsalva or cough. Unlike the urethral pressure profile, the leak point pressure reflects urethral function in the dynamic situation that produces incontinence.
Leak point pressure is used to assess intrinsic sphincter function. Leak point pressure has high reproducibility . It is more reliable than the urethral pressure profile for diagnosis of intrinsic sphincter deficiency [57-59]. Confirmation of this diagnosis can be important in selecting the correct surgical approach. Intrinsic sphincter deficiency is treated with a sling procedure or periurethral injections, rather than retropubic suspension. (See "Female stress urinary incontinence: Choosing a primary surgical procedure".)
The optimal method for performing leak point pressure is controversial. There is no standard. Variables include:
●Bladder volume (increasing volume decreases leak point) [60,61].
●Patient position (upright leak point is lower than supine).
●Catheter size (a 3 French catheter produces a lower leak point than an 8 French) .
●Location of the catheter (intravesical versus vaginal or abdominal. Transurethral catheters are obstructive and increase leak point pressure) [62,63].
●Method of determining leak point (visual, fluoroscopic or electronic).
A commonly used technique employs eight French microtip transducers at a bladder volume of 200 cc, in the sitting position, with leak point determined by visual observation. Both Valsalva and cough pressure profile (a series of increasingly strong coughs) are used to determine leak point. In the same patient, cough leak point is often different from Valsalva leak point. Furthermore, some patients involuntarily contract the levator muscles during valsalva or cough, which can increase leak point pressure. Despite these difficulties, many clinicians use a leak point pressure below 60 cm H2O to confirm the diagnosis of intrinsic sphincter deficiency .
POSTVOID RESIDUAL VOLUME — This measurement is made either by straight catheterization or by bladder ultrasound. Small portable ultrasounds specifically for postvoid residual measurement are available. A normal patient should have the ability to void at least 80 percent of the total bladder volume and have residual urine less than 50 cc immediately after voiding. A high residual urine on repeated determinations indicates outlet obstruction or poor detrusor contractility.
ELECTROPHYSIOLOGIC TESTING — Various electrophysiologic tests have also been used to evaluate lower urinary tract dysfunction. They have been employed mainly in the context of research, rather than clinical care.
●Electromyography (EMG) is the study of electrical potentials generated by depolarization of muscle. This can be done with surface electrodes, a needle inserted into urethral sphincter, a monopolar electrode inside the urethra, a concentric needle inserted into the urethral sphincter, or a single fiber to record action potentials from individual muscle fibers.
●Nerve conduction studies (NCS) examine nerve conduction rates from a stimulus to a receptor at a distal site. Pudendal nerve terminal motor latency and perineal nerve terminal motor latency (the time elapsed between initiating an impulse and its arrival at nerve's end) can be determined.
●Evoked potentials are the sum of potentials recorded in central nervous tissue (spinal cord or cortex) after stimulation of a peripheral site such as the perineum.
In clinical practice, these tests are rarely helpful except in some neurologic disorders.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Urinary incontinence in adults".)
SUMMARY AND RECOMMENDATIONS
●Full evaluation of urinary incontinence – Urodynamic testing is only one part of an evaluation that includes history, physical examination, urine culture, and postvoid residual. (See 'Indications' above.)
●Indications – Urodynamic testing is helpful when the diagnosis of lower urinary tract dysfunction is unclear, when objective findings do not correlate with subjective symptoms, when a patient fails to improve with treatment, and when surgical treatment is planned. (See 'Indications' above.)
●Test components – The main components of urodynamic testing are cystometry (measuring bladder pressure during filling of the bladder), uroflowmetry (measuring urine flow over time), pressure-flow study (determining whether poor flow is due to obstruction or detrusor weakness), and urethral pressure profile or leak point pressure (for diagnosis of intrinsic sphincter deficiency). (See 'Cystometry' above.)
●Challenges to interpretation of results – All urodynamic tests have uncontrolled variables, lack of standardization, and artifacts. Therefore, they must be interpreted with caution in the context of a patient's entire clinical picture. (See 'Common abnormalities' above.)
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