Role of Invasive Urodynamic Testing in Benign Prostatic Hyperplasia and Male Lower Urinary Tract Symptoms

The role of urodynamics in the evaluation of lower urinary tract symptoms in men with benign prostatic hyperplasia is controversial despite the additional information regarding bladder function and outlet obstruction it provides. This controversy is primarily based on outcome studies that suggest men without proved bladder outlet obstruction may benefit from outlet reduction with medication or surgical resection. The aim of this article is to describe the role of urodynamic studies in the evaluation of benign prostatic hyperplasia, including illustration of existing urodynamic techniques, reviewing best practice guidelines and current literature, and providing recommendations for use of urodynamics in clinical practice.

The goals of treatment of lower urinary tract symptoms (LUTS) and benign prostatic hyperplasia (BPH) are improvement of patient quality of life through relief of symptom-related bother and prevention of morbidities, including retention, urinary tract infections (UTIs), obstructive uropathy, and stones. When evaluating LUTS, it is helpful to divide them into storage-related issues (urinary frequency, urgency, incontinence, or nocturia) and emptying-related issues (slow stream, intermittency, hesitancy, straining, feeling of incomplete emptying, or retention). The bladder outlet obstruction caused by BPH is responsible for only a portion of the symptoms related to BPH, however. Other possible causes of LUTS in the setting of BPH include detrusor overactivity (DO), increased bladder sensation, poor compliance, and impaired detrusor contractility. The majority of the treatments for BPH, however, focus on the relief of the possible outlet obstruction. There is also general consensus that patients with proved bladder outlet obstruction have a higher success rate after treatment of BPH than those that do not. The questions raised are (1) How is the degree of outlet obstruction assessed? and (2) How are patients counseled in regards to expectations for treatment outcomes with or without the diagnosis of bladder outlet obstruction?

The American Urological Association (AUA) guidelines for treatment of BPH recommend that initial evaluation of patients includes a history and focused physical, including digital rectal examination, urinalysis, prostate-specific antigen in selected patients, and an AUA/international prostate symptom score (IPSS). Optional diagnostic testing includes uroflow and postvoid residual (PVR). These investigative tools may suggest bladder outlet obstruction, but the gold standard for diagnosis of obstruction is a pressure-flow study. Several studies have shown that only 40% to 60% of patients with suspected outlet obstruction, based on history or symptom index score, actually demonstrate true obstruction on pressure-flow studies. Also, filling cystometry during urodynamics can reveal other bladder storage dysfunction that can explain the patient symptoms that may or may not be related to obstruction. The follow-up question is, Can patients be treated empirically for BPH with medical therapy or surgical intervention without an accurate diagnosis of bladder outlet obstruction, or does the improvement in treatment outcome sufficiently justify the cost and invasiveness of a urodynamic evaluation?

The aim of this article is to describe the role of urodynamics in the evaluation of BPH, including illustration of existing urodynamic techniques, reviewing best practice guidelines and current literature, and providing recommendations for use of urodynamics in clinical practice.

Principles of urodynamics

Multichannel urodynamic studies (UDS), including filling cystometry and detrusor pressure–uroflow study, can provide important pathophysiologic information about bladder function and outlet obstruction, particularly in the setting of BPH. Bates and colleagues stated, “the bladder is an unreliable witness,” and many urologists acknowledge the difficulty in assessing men with lower urinary tract dysfunction by history and physical examination alone. Therefore, urodynamics can provide invaluable information regarding the origin and, sometimes, a better definition of a patient’s true symptoms. These studies, however, are invasive, expensive, time consuming, and bothersome for patients and, therefore, should be undertaken in a thoughtful manner with excellent quality control. The International Continence Society (ICS) outlined good urodynamic practice consisting of

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Appropriate patient selection with a clear question to be answered and clear indication for obtaining certain measurements
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Precise measurements with complete documentation and data quality control
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Accurate analysis with correlation of findings with patient symptoms

The first step in deciding to perform urodynamics is to formulate the urodynamic questions from the standard noninvasive urologic investigations, including history and physical, symptom scores, uroflowmetry, urinalysis, diary, and PVR volume. The patients’ recorded bladder diary and serial flow rates with volumes greater than 150 mL can also aid in identification of abnormal voiding patterns. These tools alone may strongly suggest the probability of bladder outlet obstruction. There may be other contributing factors, however, such as patient-reported sensation during filling, contractility, compliance, or urethral stricture disease, that are not obvious on noninvasive testing but may be suspected and, therefore, warrant further investigation. Once there exists a clear indication for UDS, the procedure is focused to allow for the collection of objective data to explain the clinical presentation.

Because the purpose of urodynamics is to identify the pathophysiology of LUTS, it is important that the study be performed interactively with patients, who are encouraged to communicate when their symptoms are reproduced. The study is also dynamic, with continuous observation of bladder pressures as they are collected and correlation of these pressures with subjective symptoms. With this in mind, the person performing UDS must have an understanding of the physics of the measurements; practical experience with the equipment, including the ability to troubleshoot problems; an understanding of quality control of signals; and the ability to analyze resulting data.

Once the indications and directed urodynamic questions are established, patients should be counseled regarding the procedure itself, including catheter placement and morbidity related to the procedure. The primary morbidity of UDS is physical discomfort. Previous studies report a risk of UTI after urodynamics with the use of prophylactic antibiotics ranging from 4% to 16%. Latthe and colleagues performed a systematic review of randomized controlled trials performed through March 2007 comparing effectiveness of prophylactic antibiotics with placebo or nothing for reducing bacteriologically proved UDS-related UTI. Eight trials with 995 patients, primarily women, were included and the investigators found a 40% reduction in risk of significant bacteriuria (colony count >10 ⁵/mL). The antibiotics used included nitrofurantoin, floroquinolones, augmentin, trimethoprim, and cotrimazole and most were given before the study. Patients have also reported low rates of transient micturition pain and difficulty voiding, which is usually more pronounced in men than women; hematuria; cloudy urine; and fever. Despite these morbidities, when patient-reported discomfort, embarrassment, and apprehension were investigated, 33% to 70% of men reported only mild pain and 74% to 95% of men reported they would undergo urodynamics again if medically indicated. Important factors that have been identified to reduce patient discomfort and anxiety include the ability of a physician to communicate and explain during the procedure and the level of expertise in technique when performing UDS.

In preparation for urodynamic evaluation, a 7 to 10F transurethral dual lumen catheter is placed into the bladder and connected to an external pressure transducer to measure bladder pressure (Pves). A separate rectal balloon catheter is placed for the measurement of abdominal pressure (Pabd). True detrusor pressure (Pdet) is a calculation subtracting Pabd from Pves and represents a true rise in detrusor pressure independent of the effect of increased abdominal pressure (ie, during Valsalva’s maneuver). “Zero pressure” should be the value recorded when the open end of the fluid-filled bladder catheter, connected to the transducer, is at the same vertical level as the transducer. The transducer should be set at the reference height, which is at the level of the upper edge of the symphysis pubis. Patients can be catheterized in the supine position, but the test should be performed in the upright position if patients are able to stand, to mimic the stresses on the bladder when patients are vertical. Also, whatever activity precipitates a patient’s symptoms, including change of position, hearing water run, and so forth, should be replicated during the study.

Indications for urodynamics

The role of urodynamics in the evaluation of LUTS in men with BPH remains controversial despite its provision of potentially useful information regarding bladder function and outlet obstruction. This controversy is primarily based on outcome studies that have confirmed men without proved bladder outlet obstruction may still benefit from relaxation of the bladder outlet with medication or surgical resection. There is evidence that men with obstruction fare better in symptom reduction, including decreased bother impact and improvement in quality of life after ablative prostate surgery than those without obstruction. The difference in surgical success rates for men with demonstrable outlet obstruction is 15% to 29% higher than in those patients without obstruction. Despite this, unobstructed men do not always fail, with moderate success rates of 55% to 78%. Tanaka and colleagues studied the predictive value of UDS regarding efficacy of transurethral resection of prostate (TURP) at 3 months based on IPSS, quality-of-life questionnaires, and improvement of maximum flow rate (Qmax). Their finding was that as the degree of outlet obstruction worsened, TURP efficacy improved. Unobstructed patients with DO improved only minimally after TURP. Jensen and colleagues also studied the predictive value of UDS for the outcome of prostatic surgery in 130 men, finding that at 6 months the success rate was 93% as opposed to 78% in unobstructed patients ( P <.02). These investigators followed up on the same patients 8 years later and reviewed their symptom score analysis, uroflowmetry, and subjective evaluation of outcome. The difference in success rates was less impressive but persisted in long-term outcomes at 8 years: 83% in obstructed men versus 72% in men with no obstruction.

Urodynamic evaluation, therefore, can be a valuable tool in the evaluation of BPH in providing a pathophyisiologic explanation of symptoms and guidance for therapeutic management. When counseling patients for treatment outcome expectations, urodynamics can also help predict response to various treatments. When symptoms and initial evaluation strongly suggest that obstruction is present (ie, low flow rate, large prostate on digital rectal examination, primarily obstructive complaints on the AUA/IPSS scoring, and elevated PVRs), then patients may be treated for obstruction on an empiric basis (ie, omitting UDS from the evaluation). If patients have other health-related issues affecting voiding function, however (eg, diabetes; cerebrovascular disease; other neurologic disorders, such as multiple sclerosis or Parkinson’s disease; or history of pelvic radiation), urodynamic evaluation seems prudent. The authors agree with European Association of Urology (EAU) guidelines recommending pressure-flow studies before prostatectomy under the following circumstances:

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Voided volume <150 mL or Qmax >15 mL, particularly if patients are elderly
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Younger men (ie, <50 years old)
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Elderly men (ie, >80 years old)
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PVR >300 mL
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Suspicion of neurogenic bladder (ie, Parkinson’s disease)
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After radical pelvic surgery
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Previous unsuccessful invasive treatment

The urodynamic evaluation is a tool in a urologist’s armamentarium that must be used in perspective of the complete picture. Urologists should be wary of making decisions based on a single office visit and urodynamic findings (essentially a snapshot of a particular patient) because BPH is a dynamic process that may change with time.

One situation in which urodynamic evaluation is imperative is in men with significant LUTS persisting after TURP. The majority of these symptoms are related to detrusor dysfunction and not obstruction and, therefore, may require strategies other than those treating the bladder outlet. Nitti and colleagues and Thomas and colleagues found only a small percentage of men (12%–16%) who returned after TURP had persistent obstruction. Detrusor dysfunction may be in the form of involuntary detrusor activity during filling or detrusor underactivity that only is elucidated during a urodynamic study. LUTS persisting or recurring after TURP are explained by DO in the absence of obstruction 50% of the time in patients with concomitant neurologic disorders. Detrusor underactivity, alternatively, may be related to long-term obstruction or age-related changes, which may have been present before intervention and continue to progress despite relief of obstruction. In studying factors predictive of detrusor underactivity after TURP, Thomas and colleagues only identified lower preoperative voiding pressures, similar to the findings of Neal and colleagues. When this information is obtained before initial resection or after a patient returns with persistent symptoms, a urologist can better direct therapy and expectations.

Indications for urodynamics

The role of urodynamics in the evaluation of LUTS in men with BPH remains controversial despite its provision of potentially useful information regarding bladder function and outlet obstruction. This controversy is primarily based on outcome studies that have confirmed men without proved bladder outlet obstruction may still benefit from relaxation of the bladder outlet with medication or surgical resection. There is evidence that men with obstruction fare better in symptom reduction, including decreased bother impact and improvement in quality of life after ablative prostate surgery than those without obstruction. The difference in surgical success rates for men with demonstrable outlet obstruction is 15% to 29% higher than in those patients without obstruction. Despite this, unobstructed men do not always fail, with moderate success rates of 55% to 78%. Tanaka and colleagues studied the predictive value of UDS regarding efficacy of transurethral resection of prostate (TURP) at 3 months based on IPSS, quality-of-life questionnaires, and improvement of maximum flow rate (Qmax). Their finding was that as the degree of outlet obstruction worsened, TURP efficacy improved. Unobstructed patients with DO improved only minimally after TURP. Jensen and colleagues also studied the predictive value of UDS for the outcome of prostatic surgery in 130 men, finding that at 6 months the success rate was 93% as opposed to 78% in unobstructed patients ( P <.02). These investigators followed up on the same patients 8 years later and reviewed their symptom score analysis, uroflowmetry, and subjective evaluation of outcome. The difference in success rates was less impressive but persisted in long-term outcomes at 8 years: 83% in obstructed men versus 72% in men with no obstruction.

Urodynamic evaluation, therefore, can be a valuable tool in the evaluation of BPH in providing a pathophyisiologic explanation of symptoms and guidance for therapeutic management. When counseling patients for treatment outcome expectations, urodynamics can also help predict response to various treatments. When symptoms and initial evaluation strongly suggest that obstruction is present (ie, low flow rate, large prostate on digital rectal examination, primarily obstructive complaints on the AUA/IPSS scoring, and elevated PVRs), then patients may be treated for obstruction on an empiric basis (ie, omitting UDS from the evaluation). If patients have other health-related issues affecting voiding function, however (eg, diabetes; cerebrovascular disease; other neurologic disorders, such as multiple sclerosis or Parkinson’s disease; or history of pelvic radiation), urodynamic evaluation seems prudent. The authors agree with European Association of Urology (EAU) guidelines recommending pressure-flow studies before prostatectomy under the following circumstances:

▪

Voided volume <150 mL or Qmax >15 mL, particularly if patients are elderly
▪

Younger men (ie, <50 years old)
▪

Elderly men (ie, >80 years old)
▪

PVR >300 mL
▪

Suspicion of neurogenic bladder (ie, Parkinson’s disease)
▪

After radical pelvic surgery
▪

Previous unsuccessful invasive treatment

The urodynamic evaluation is a tool in a urologist’s armamentarium that must be used in perspective of the complete picture. Urologists should be wary of making decisions based on a single office visit and urodynamic findings (essentially a snapshot of a particular patient) because BPH is a dynamic process that may change with time.

One situation in which urodynamic evaluation is imperative is in men with significant LUTS persisting after TURP. The majority of these symptoms are related to detrusor dysfunction and not obstruction and, therefore, may require strategies other than those treating the bladder outlet. Nitti and colleagues and Thomas and colleagues found only a small percentage of men (12%–16%) who returned after TURP had persistent obstruction. Detrusor dysfunction may be in the form of involuntary detrusor activity during filling or detrusor underactivity that only is elucidated during a urodynamic study. LUTS persisting or recurring after TURP are explained by DO in the absence of obstruction 50% of the time in patients with concomitant neurologic disorders. Detrusor underactivity, alternatively, may be related to long-term obstruction or age-related changes, which may have been present before intervention and continue to progress despite relief of obstruction. In studying factors predictive of detrusor underactivity after TURP, Thomas and colleagues only identified lower preoperative voiding pressures, similar to the findings of Neal and colleagues. When this information is obtained before initial resection or after a patient returns with persistent symptoms, a urologist can better direct therapy and expectations.

Filling cystometry

This portion of the urodynamic evaluation is integral for the detection of abnormal bladder compliance, increased bladder sensation, and DO. Approximately 20% to 40% of men with BPH have demonstrable DO, possibly related to long-term obstruction or age-associated detrusor changes.

Cystometry should be performed only as a part of a pressure-flow study when evaluating men with LUTS/BPH and not as a stand-alone test. The procedure involves filling the bladder with room temperature (22 °C) or body temperature (37 °C) sterile water or saline at a rate of 10 to 50 mL/min (depending on voided volumes as gleaned by voiding diary analysis) while bladder and abdominal pressures are simultaneously recorded. The first sensation of filling, first desire to void, and strong desire to void should be recorded to reflect presence or absence of sensation reduction or amplification (first sensation of filling <100 mL). Changes in bladder pressure during filling should be noted as to correspondence with urgency or other symptoms.

Normally, the bladder should store urine at low pressure without involuntary detrusor contractions and normal compliance (>40 mL/cm H ₂O). Fig. 1 demonstrates involuntary detrusor contraction during filling (DO). DO in men with BPH has been shown to be independently associated with aging and degree of obstruction. Oelke and colleagues studied 1481 men with BPH and LUTS; after age adjustment, the odds ratios of DO compared with Schäfer’s obstruction grade (0–VI) were: 1.2 for grade I, 1.4 for grade II, 1.9 for grade III, 2.5 for grade IV, 3.4 for grade V, and 4.7 for grade VI. Furthermore, men with BPH and DO tend to have decreased compliance and capacity. Gomes and colleagues measured a difference of 31 mL/cm H ₂O in bladder compliance and 120 mL in mean capacity between men with and without DO having undergone UDS for evaluation of BPH, both statistically significant differences. Men with DO have a higher risk of failure to improve symptom-related bother after prostatectomy than those that do not, particularly if no bladder outlet obstruction is identified. When a patient reports significant storage-related symptoms and when DO and bladder outlet obstruction are present on UDS, a urologist may counsel the patient that these symptoms resolve approximately two thirds of the time after outlet-reducing surgery. If DO persists, the patient may require further treatment with anticholinergic medication or other lower urinary tract rehabilitation to reduce bladder overactivity.