Lower urinary tract symptoms are common in men, and an accurate diagnosis of bladder outlet obstruction would help reduce invasive testing and initiate targeted treatment to improve symptoms and reduce complications.
A review by Dr. Silva of St Michael’s Hospital in Canada examines the diagnosis of bladder outlet obstruction based on patient symptoms and the ability of cystometry to accurately measure residual urine. The article was published online in the August 6 issue of JAMA.
Clinical Case
The patient was a 72-year-old male who needed to get up 3 times a night to urinate. He has had nocturia for the past several years, which has recently worsened. In addition to a feeling of bladder fullness, he has had difficulty urinating and a thin urine stream in the last few months. During the week of the visit, there were several episodes of urinary incontinence. There is no hematuria, no painful urination, no history of urinary tract infection, and no history of other prostate or urinary tract disease.
When evaluating this patient, which lower urinary tract symptom do you think is most suggestive of bladder outlet obstruction?
Background
Bladder outlet obstruction can cause many clinical symptoms, including urinary frequency, thinning of the urine stream, and a feeling of incomplete urination. These symptoms are known as lower urinary tract symptoms.
Lower urinary tract symptoms include voiding symptoms and obstructive symptoms such as hesitant urination, thin or intermittent urine stream (or possibly both), straining to urinate, dribbling, and prolonged urination; as well as storage symptoms and urinary tract irritation such as frequency, urgency, urge incontinence, and nocturia. The most common lower urinary tract symptoms reported in the literature include hesitancy to urinate, thinning of the urine stream, and nocturia.
Prostatic hyperplasia (BPH) frequently causes lower urinary tract symptoms and is very common in older men over 60 years of age. The prevalence of BPH is 90% in people aged 81 to 90 years.
BPH is associated with benign hyperplasia of smooth muscle cells and epithelial cells in the migratory zone of the prostate. The migratory zone of the prostate has 2 lobes that encircle the proximal urethra. The prostate is adjacent to the bladder neck and wraps around the prostatic portion of the urethra. Cellular hyperplasia increases the size of the migratory zone, compressing the urethra and causing bladder outlet obstruction, which can lead to lower urinary tract symptoms. However, BPH does not always cause bladder outlet obstruction, and patients may be asymptomatic.
There are many causes of lower urinary tract symptoms in older men, including structural and functional abnormalities of the lower urinary tract, which (in addition to BPH) are equally important.
Causes of lower urinary tract symptoms (other than bladder outflow tract obstruction secondary to BPH)
Urethral stricture
primary bladder neck obstruction
bladder neck contracture
Urethral stricture
Bladder dysfunction (e.g., overactive bladder syndrome)
Urinary tract infection
Neoplastic disease (e.g. bladder cancer, prostate cancer)
Chronic pelvic pain (e.g., prostatitis, interstitial cystitis)
Medications (e.g., diuretics)
Other disease states (e.g., congestive heart failure)
Central nervous system dysfunction
Stroke
Parkinson’s disease
Some prescription medications, such as antidepressants, antihistamines, bronchodilators, anticholinergics, and sympathomimetics, may also cause or exacerbate lower urinary tract symptoms because they can act on the forceps and urethral dilators.
Contractile dysfunction of the detrusor muscle in patients with overactive bladder can cause lower urinary tract symptoms by itself or may be combined with other conditions causing lower urinary tract symptoms. In some patients, if bladder outlet obstruction is suspected but not effective for treatment, the etiology of lower urinary tract symptoms in these patients is often overactive bladder disorder.
We emphasize the importance of identifying the underlying cause of bladder outlet obstruction which, if left untreated, may lead to a number of complications. These complications include recurrent urinary tract infections, bladder stones, overflow incontinence, meatus hematuria, pelvic effusion, acute urinary retention, and nephropathy.
Complications associated with bladder outlet obstruction affect patients’ quality of life and increase the number of patient visits. in 2000, approximately 8 million outpatient visits in the United States had a primary or secondary diagnosis of BPH.
A Canadian population-based assessment suggested that outpatient visits for patients with bladder outlet obstruction increased by 50% from 2000 to 2004. The direct medical costs of treating BPH in the United States in 2000 were $1.1 billion (including costs incurred in outpatient clinics, inpatient units, emergency departments, and physicians’ offices).
Most patients who first present with lower urinary tract symptoms visit a primary care physician. Identifying risk factors associated with bladder outlet obstruction at the initial visit will help identify patients with complications who may benefit from treatment (alpha blockers, 5-alpha reductase inhibitors, or both) or referral to a specialist to avoid complications.
The diagnostic test for bladder outlet obstruction is an invasive pressure/urinary flow rate measurement, known as urodynamics, which is usually performed by a urologist.
The urodynamic test is performed in 2 time phases, namely urine storage at low bladder pressure (filling phase) and effective spontaneous emptying (voiding phase), and the primary function of the bladder is assessed based on its results. The examination involves the insertion of a small catheter through the urethra and the slow filling of the bladder with saline while measuring the intravesical pressure. In addition, a transrectal transducer is inserted to measure intra-abdominal pressure.
During voiding, measurement of urinary flow rate and forced urinary muscle pressure (i.e., intravesical pressure seen minus intra-abdominal pressure) allows calculation of many parameters of bladder outlet resistance, such as the Abrams-Griffiths diagram, which can help in the diagnosis of bladder outlet obstruction. In bladder outlet obstruction, the intravesical pressure is high and the urinary flow rate is low (high pressure – low flow type), so the forceps pressure during voiding can reflect the bladder outlet resistance.
In the A-G diagram, the forced urinary muscle pressure is used to determine whether the bladder outlet is obstructed, or suspected of being obstructed, based on the maximum urinary flow rate during voiding.
Quantifying lower urinary tract symptoms can provide important information for clinical workups, such as disease severity, response to treatment, and progression of clinical symptoms. Many questionnaires exist, but the most important is the American Urological Association Symptom Index (AUA Symptom Index), often referred to as the International Prostate Symptom Score (IPSS, see Table 2).
This questionnaire was designed in 1992 and was originally used to assess the severity of BPH symptoms. in 1993, the WHO added a question to the AUA Symptom Index7 questions, now known as the distress score, to assess how much the symptoms bothered them.
Urinary tract symptoms
1. Dysuria: In the past month, have you experienced frequent dysuria after urination?
2. Frequency: In the past month, did you often urinate again within 2 hours after urination?
3. Interrupted urine flow: In the past month, have you often experienced multiple interruptions in your urine flow during urination and then restarted urination?
4. Urinary urgency: In the past month, have you had difficulty holding your urine?
5. Thinner urine stream: In the past month, have you often experienced a thinner urine stream?
6. Effort to urinate: In the past month, did you often need to strain or exert yourself to start urinating?
7. Nocturia: In the past month, how many times did you need to get up to urinate from the time you went to sleep to the time you got up?
Scoring.
Items 1-6: 0 points, not once; 1 point, less than 1 out of 5 times; 2 points, less than half; 3 points, about half; 4 points, more than half; 5 points, almost every time.
Item 7: 0 points, none; 1 point, 1 time; 2 points, 2 times; 3 points, 3 times; 4 points, 4 times; 5 points, 5 times.
Total score: 0-7 points, mild symptoms; 8-19 points moderate symptoms; 20-35 points severe symptoms.
Quality of life
How would you feel if your future life was accompanied by your current urination situation?
Score: 0, happy; 1, satisfied; 2, generally satisfied; 3, okay (both full and unsatisfied); 4, not very satisfied; 5, unsatisfied; 6, poor
The names IPSS and AUA Symptom Index are interchangeable, and this review uses the IPSS. first symptoms of bladder outlet obstruction are usually seen by a non-specialist or primary care physician, so it is important to assess the diagnostic accuracy of commonly used screening methods.
The primary objective of this review was to evaluate the diagnostic accuracy of individual symptoms and questionnaires in men with lower urinary tract symptoms relative to urodynamic testing (the reference standard, “gold standard”).
The second objective was to assess the relevance of cystometry and catheterization for measuring residual urine volume. Normal bladder function allows complete voiding without residual urine, or no residual urine after voiding.
Therefore an increase in residual urine volume after voiding reflects a decline in bladder emptying function.
Although there is no standard definition of residual urine volume, the currently accepted standard is less than 200 ml. Residual urine volumes in excess of 200 ml are indicative of reduced bladder emptying, which is a risk factor for urinary tract infection. Declining bladder function may lead to long-term complications such as acute renal failure and urinary retention.
Review of the literature
By searching the literature of prospective studies between 1950-2014 on diagnostic tests for men with lower urinary tract symptoms due to bladder outlet obstruction and comparing cystometric and catheter methods for measuring residual urine, 10 and 20 publications were used according to the inclusion criteria, respectively.
The quality of the literature was graded according to the Quality Assessment of Diagnostic Accuracy Studies 2 criteria, with grade 1 being the highest quality and grade 5 being the worst.
1. Prevalence of bladder outlet obstruction
The results of the Level 3 quality studies showed that more than half of the patients with lower urinary tract symptoms had bladder outlet obstruction (total prevalence: 64%).
The highest prevalence among all levels of quality studies was 79% (level 3 quality) and the lowest was 38% (level 4 quality).
2. Accuracy of diagnosis of bladder outlet obstruction based on symptoms
The studies included in this review considered a number of different lower urinary tract symptoms, including thin urine stream, nocturia, urinary frequency, urinary urgency, intermittent urine stream, urge incontinence, straining to urinate, dribbling after urination, hesitation to urinate, and a sense of incompleteness.
Of these symptoms, only intermittent urine flow and post-void dribbling were assessed in the Level 3 studies, but the 95% confidence interval for the likelihood ratio included 1.
In poorer quality studies, urinary incontinence and thinning of the urine stream increased the likelihood ratio for bladder outlet obstruction, but patients without nocturia symptoms seemed less likely to have bladder outlet obstruction.
IPSS is the most commonly used metric in high quality studies, with IPSS >= 20 or IPSS >= 8 usually used as a cut-off value to predict the presence of bladder outlet obstruction (Table -3).
The positive predictive value for bladder outlet obstruction is only slightly higher with increasing diagnostic threshold, but even above an IPSS score of 20, the positive predictive value is only 1.5.
Similarly, the ability of the IPSS to rule out bladder outlet obstruction improved as symptoms decreased. However, even at the lowest threshold (IPSS<8), the negative likelihood ratio was only 0.58.
Thus, IPSS is not very useful in predicting bladder outlet obstruction in patients with lower urinary tract symptoms, and its use in clinical practice is therefore limited.
Summary of the accuracy of IPSS and symptoms in diagnosing bladder outlet obstruction
Threshold of diagnostic tests
Sensitivity
Specificity
Positive Likelihood Ratio
Negative Likelihood Ratio
Diagnostic OR
IPSS/AUA Symptom >=20
41 (30-52)
71 (63-78)
1.5 (1.1-2.0)
0.82 (0.67-1.00)
1.8 (1.2-2.8)
IPSS ≥14
69 (58-79)
41 (31-52)
1.20 (0.93-1.50)
0.75 (0.49-1.10)
1.60 (0.82-3.00)
IPSS/AUA Symptom Index ≥8
91 (85-95)
12 (8-19)
1.00 (0.89-1.10)
0.58 (0.28-1.20)
1.60 (0.49-5.40)
3. Accuracy of physical examination in diagnosing bladder outlet obstruction
Rectal examination was performed in many studies, but there are no data on the diagnostic accuracy. Some studies performed rectal finger examination or bladder percussion and compared it with the reference standard for bladder outlet obstruction, but none of them met the inclusion criteria of this study.
4. Accuracy of cystometry in assessing urine volume
A search of the literature screened 20 publications for inclusion in the study, 8 of which explored the correlation between measured urine volume and pre-void urine volume.
The overall correlation coefficient was r=0.93, suggesting a high correlation between cystometric results of catheterization measurements. Despite the heterogeneity in the literature, there was no evidence of publication bias.
5. Limitations of the study
Studies of diagnostic accuracy are usually at risk of case selection bias.
In addition, the small number of publications included in this review, the small sample of the original studies themselves, and the lack of urodynamic studies using blinded, independent methods are limitations of this review.
The results of these studies suggest that examination is more likely to produce differences when urine volumes are higher. However, the purpose of our examination of residual urine volume is to see if there is significant urinary retention, and thus these differences are usually not clinically relevant.
Both cystometry and urethral cannula techniques for measuring residual urine have limitations in the presence of pathologic structures. When urine volume is close to the diagnostic threshold, caution should be exercised and relevant series should be performed to avoid the effects of instrumental measurements and daily urine volume variability.
6. Discussion
The positive likelihood ratios (LR) of questionnaires and symptoms suggest that they are of little significance for the diagnosis of bladder outlet obstruction. Lower urinary tract symptoms in men are usually caused by the presence of prostatic hyperplasia, which leads to bladder outlet obstruction.
The questionnaire lacks specificity in identifying other etiologies of lower urinary tract symptoms, such as medications, neurological, renal, cardiovascular and respiratory diseases or dysfunctions, and therefore does not correctly diagnose bladder outlet obstruction.
The IPSS has limitations due to cultural differences in patient education, cognitive ability, and perception of sensory perception, possible reluctance of patients to fill out the questionnaire truthfully, and possible inaccuracy in recalling symptoms.
Patients’ co-morbidities, medication use, and water deprivation may cause symptoms to fluctuate. These may affect the accurate classification of disease severity. Once a patient is diagnosed, the IPSS can be a reliable tool to reflect response to treatment.
Although the Urological Association recommends rectal examination and PSA first for men with lower urinary tract symptoms, this review concludes that there is a lack of evidence for these findings as a marker of bladder outlet obstruction. The value of these diagnostic tests for other conditions is beyond the scope of this review.
Case Analysis
Lower urinary tract symptoms are very common and are not exclusively seen in older men. Based on the findings in this review, the pretest probability of bladder outlet obstruction in this 72-year-old male patient was estimated to be 64%. His IPSS score was 21 (bladder emptying = 4, frequency = 2, intermittent urine flow = 2, urgency = 2, thinning of urine flow = 5, straining to urinate = 3, nocturia = 3) and quantified the intensity of symptoms.
There were no positive results for a complete history, physical examination (including rectal examination), and focused tests to assess voiding function (infections, medications, other systemic diseases, and possible neoplastic diseases). According to the results in the table, an IPSS greater than 20 gives a positive predictive value of 1.5, which gives a post-test probability of 73% for bladder outlet obstruction.
The IPSS quantifies the severity of the symptoms and the degree of distress to the patient. Residual urine volume greater than 350 ml measured by cystometry after voiding suggests bladder emptying dysfunction, the latter being a risk factor for urinary tract infection, which may be secondary to hydronephrosis, acute kidney disease and urinary retention. The results of the cystometry are highly correlated with the results of catheterization and therefore can be done without catheterization.
The patient was referred to a urologist and treatment with alpha-blockers and 5-alpha reductase inhibitors was started. The result was only a mild improvement in symptoms. The latest clinical guidelines recommend a urodynamic study to confirm bladder outlet obstruction prior to invasive cautery therapy such as transurethral resection of the prostate. Therefore, the patient underwent urodynamic testing and was diagnosed with bladder outlet obstruction.
After thorough consideration of the benefits, risks, complications, and alternatives such as laser cautery, the patient underwent transurethral resection of the prostate. 3-month follow-up revealed an improvement in urinary flow symptoms and voiding sensation with an IPSS score of 8.
Key Points
In men with lower urinary tract symptoms, the IPSS quantifies the severity of symptoms while taking into account the distress caused by these symptoms. However, neither the lower urinary tract symptoms nor the IPSS had better accuracy in predicting bladder outlet obstruction.
With the high prevalence of bladder outlet obstruction in men with lower urinary tract symptoms, cystometry provides a non-invasive and reliable method to help determine the presence of post-void urine retention. It therefore avoids the need to insert a urinary catheter and provides an effective tool to perform a series of tests to assess urinary volume changes and detect disease progression.