Primary care physicians are uniquely positioned to screen for benign prostatic hyperplasia (BPH) and lower urinary tract symptoms, to perform the initial diagnostic workup, and to start medical therapy in uncomplicated cases. Effective medical therapy is available but underutilized in the primary care setting.1
This overview covers how to identify and evaluate patients with lower urinary tract symptoms, initiate therapy, and identify factors warranting timely urology referral.
TWO MECHANISMS: STATIC, DYNAMIC
BPH is a histologic diagnosis of proliferation of smooth muscle, epithelium, and stromal cells within the transition zone of the prostate,2 which surrounds the proximal urethra.
Symptoms arise through two mechanisms: static, in which the hyperplastic prostatic tissue compresses the urethra (Figure 1); and dynamic, with increased adrenergic nervous system and prostatic smooth muscle tone (Figure 2).3 Both mechanisms increase resistance to urinary flow at the level of the bladder outlet.
As an adaptive change to overcome outlet resistance and maintain urinary flow, the detrusor muscles undergo hypertrophy. However, over time the bladder may develop diminished compliance and increased detrusor activity, causing symptoms such as urinary frequency and urgency. Chronic bladder outlet obstruction can lead to bladder decompensation and detrusor underactivity, manifesting as incomplete emptying, urinary hesitancy, intermittency (starting and stopping while voiding), a weakened urinary stream, and urinary retention.
MOST MEN EVENTUALLY DEVELOP BPH
Autopsy studies have shown that BPH increases in prevalence with age beginning around age 30 and reaching a peak prevalence of 88% in men in their 80s.4 This trend parallels those of the incidence and severity of lower urinary tract symptoms.5
In the year 2000 alone, BPH was responsible for 4.5 million physician visits at an estimated direct cost of $1.1 billion, not including the cost of pharmacotherapy.6
BPH can cause lower urinary tract symptoms that fall into two categories: storage and emptying. Storage symptoms include urinary frequency, urgency, and nocturia, whereas emptying symptoms include weak stream, hesitancy, intermittency, incomplete emptying, straining, and postvoid dribbling.
History and differential diagnosis
Assessment begins with characterizing the patient’s symptoms and determining those that are most bothersome. Because BPH is just one of many possible causes of lower urinary tract symptoms, a detailed medical history is necessary to evaluate for other conditions that may cause lower urinary tract dysfunction or complicate its treatment.
Obstructive urinary symptoms can arise from BPH or from other conditions, including urethral stricture disease and neurogenic voiding dysfunction.
Irritative voiding symptoms such as urinary urgency and frequency can result from detrusor overactivity secondary to BPH, but can also be caused by neurologic disease, malignancy, initiation of diuretic therapy, high fluid intake, or consumption of bladder irritants such as caffeine, alcohol, and spicy foods.
Urinary frequency is sometimes a presenting symptom of undiagnosed or poorly controlled diabetes mellitus resulting from glucosuria and polyuria. Iatrogenic causes of polyuria include the new hypoglycemic agents canagliflozin and dapagliflozin, which block renal glucose reabsorption, improving glycemic control by inducing urinary
Nocturia has many possible nonurologic causes including heart failure (in which excess extravascular fluid shifts to the intravascular space when the patient lies down, resulting in polyuria), obstructive sleep apnea, and behavioral factors such as high evening fluid intake. In these cases, patients usually have nocturnal polyuria (greater than one-third of 24-hour urine output at night) rather than only nocturia (waking at night to void). A fluid diary is a simple tool that can differentiate these two conditions.
Hematuria can develop in patients with BPH with bleeding from congested prostatic or bladder neck vessels; however, hematuria may indicate an underlying malignancy or urolithiasis, for which a urologic workup is indicated.
The broad differential diagnosis for the different lower urinary tract symptoms highlights the importance of obtaining a thorough history.
A general examination should include the following:
Body mass index. Obese patients are at risk of obstructive sleep apnea, which can cause nocturnal polyuria.
Gait. Abnormal gait may suggest a neurologic condition such as Parkinson disease or stroke that can also affect lower urinary tract function.
Lower abdomen. A palpable bladder suggests urinary retention.
External genitalia. Penile causes of urinary obstruction include urethral meatal stenosis or a palpable urethral mass.
Digital rectal examination can reveal benign prostatic enlargement or nodules or firmness, which suggest malignancy and warrant urologic referral.
Neurologic examination, including evaluation of anal sphincter tone and lower extremity sensorimotor function.
Feet. Bilateral lower-extremity edema may be due to heart failure or venous insufficiency.
The International Prostate Symptom Score
All men with lower urinary tract symptoms should complete the International Prostate Symptom Score (IPSS) survey, consisting of seven questions about urinary symptoms plus one about quality of life.8 Specifically, it asks the patient, “Over the past month, how often have you…”
- Had a sensation of not emptying your bladder completely after you finish urinating?
- Had to urinate again less than 2 hours after you finished urinating?
- Found you stopped and started again several times when you urinated?
- Found it difficult to postpone urination?
- Had a weak urinary stream?
- Had to push or strain to begin urination?
Each question above is scored as 0 (not at all), 1 (less than 1 time in 5), 2 (less than half the time), 3 (about half the time), 4 (more than half the time, or 5 (almost always).
- Over the past month, how many times did you most typically get up to urinate from the time you went to bed until the time you got up in the morning?
This question is scored from 0 (none) to 5 (5 times or more).
- If you were to spend the rest of your life with your urinary condition the way it is now, how would you feel about that?
This question is scored as 0 (delighted), 1 (pleased), 2 (mostly satisfied), 3 (mixed: equally satisfied and dissatisfied), 4 (mostly dissatisfied), 5 (unhappy), or 6 (terrible).
A total score of 1 to 7 is categorized as mild, 8 to 19 moderate, and 20 to 35 severe.
The questionnaire can also be used to evaluate for disease progression and response to treatment over time. A change of 3 points is clinically significant, as patients are unable to discern a difference below this threshold.9
Urinalysis is recommended to assess for urinary tract infection, hematuria, proteinuria, or glucosuria.
A fluid diary is useful for patients complaining of frequency or nocturia and can help quantify the volume of fluid intake, frequency of urination, and volumes voided. The patient should complete the diary over a 24-hour period, recording the time and volume of fluid intake and each void. This aids in diagnosing polyuria (> 3 L of urine output per 24 hours), nocturnal polyuria, and behavioral causes of symptoms, including excessive total fluid intake or high evening fluid intake contributing to nocturia.
Serum creatinine not recommended
Measuring serum creatinine is not recommended in the initial BPH workup, as men with lower urinary tract symptoms are not at higher risk of renal failure than those without these symptoms.10