From: The Merck Manual of Diagnosis and Therapy

Benign Prostatic Hyperplasia

(Benign Prostatic Hypertrophy)

Benign adenomatous hyperplasia of the periurethral prostate gland, causing variable degrees of bladder outlet obstruction.

A major difficulty in establishing prevalence of benign prostatic hyperplasia (BPH) has been the lack of a common definition. Based on autopsy studies, the prevalence of histologically diagnosed BPH increases from 8% in men aged 31 to 40 yr to 40 to 50% in men aged 51 to 60 yr and > 80% in men older than 80 yr. However, based on clinical criteria in men aged 55 to 74 yr without prostate cancer, the prevalence of BPH is 19% using the criteria of a prostate volume > 30 mL and a high International Prostate Symptom score. However, the prevalence is only 4% if the criteria are a prostate volume > 30 mL, a high score, a maximal urinary flow rate < 10 mL/sec, and a postvoid residual urine volume > 50 mL.

Etiology and Pathophysiology

The etiology is unknown but may involve hormonal changes associated with aging. Multiple fibroadenomatous nodules occur in the periurethral region of the prostate gland, probably originating within the periurethral glands rather than in the true fibromuscular prostate (surgical capsule), which is displaced peripherally by progressive growth of the nodules. The hyperplasia may involve the lateral walls of the prostate (lateral lobe hyperplasia) or tissue at the inferior margin of the vesical neck (middle lobe hyperplasia). Histologically, the tissue is glandular, with varying proportions of fibrous stroma interposed.

As the lumen of the prostatic urethra becomes compromised, urine outflow is progressively obstructed, accompanied by hypertrophy of the bladder detrusor, trabeculation, cellule formation, and diverticula. Incomplete bladder emptying causes stasis and predisposes to infection with secondary inflammatory changes in the bladder (chronic prostatitis, see below) and the upper urinary tract. Urinary stasis predisposes to calculus formation (see Ch. 221). Prolonged obstruction, although incomplete, can produce hydronephrosis and compromise renal function.

Symptoms, Signs, and Diagnosis

Progressive urinary frequency, urgency, and nocturia are due to incomplete emptying and rapid refilling of the bladder. Decreased size and force of the urinary stream produce hesitancy and intermittency. Sensations of incomplete emptying, terminal dribbling, almost continuous overflow incontinence, or complete urinary retention may ensue. Straining to void can cause congestion of superficial veins of the prostatic urethra and trigone, which may rupture and produce hematuria. Acute complete urinary retention may be precipitated by prolonged attempts to retain urine, immobilization, exposure to cold, anesthetics, anticholinergic and sympathomimetic drugs, or ingestion of alcohol. Symptoms may be quantitated by the seven-question American Urological Association Symptom Score (see Table 218-1).

On rectal examination, the prostate usually is enlarged, has a rubbery consistency, and, frequently, has lost the median furrow. However, digital rectal examination of prostate size may be misleading. A small prostate on rectal examination may be sufficiently large to cause obstruction. The distended urinary bladder may be palpable or percussible on physical examination.

Serum prostate-specific antigen (PSA) is moderately elevated in 30 to 50% of patients with BPH, depending on prostate size and degree of obstruction (see also Prostate Cancer in Ch. 233). Men with mild or moderate BPH symptoms usually do not need further testing.

More severe symptoms or the presence of hematuria or UTI warrants further evaluation by a urologist. IVU may disclose upward displacement of the terminal portions of the ureters (fishhooking) and a defect at the base of the bladder compatible with prostatic enlargement. With prolonged obstruction, the ureters dilate and hydronephrosis occurs. Urethral catheterization cystoscopy or ultrasonography after voiding measures residual urine, and catheterization permits preliminary drainage to stabilize renal function and adequately control UTI. If indicated because of an elevated serum PSA, transrectal ultrasonography permits estimation of gland size, may aid selection of the appropriate surgical approach, and differentiates vesical neck contracture, chronic prostatitis, and other obstructive phenomena. Instrumentation should be avoided until definitive therapy has been decided, because manipulation may increase obstruction, trauma, and infection.

An indurated and tender prostate suggests prostatitis, whereas a stony, hard, nodular prostate usually indicates carcinoma or, occasionally, prostatic calculi.

Treatment

When BPH is associated with UTI or azotemia due to bladder outlet obstruction, initial therapy should be medical, directed toward stabilizing renal function, discontinuing anticholinergic and sympathomimetic drugs, and eradicating infection. Urethral or suprapubic catheter drainage may be desirable in advanced bladder outlet obstruction. The chronically obstructed, distended bladder should be slowly decompressed to help avoid postobstructive diuresis. For some patients with mild to moderate obstructive symptoms, -adrenergic blockers such as terazosin may improve voiding. The 5-reductase inhibitor finasteride may reduce prostate size, improving voiding over time (months), especially in patients with large (> 40 mL) glands. All such patients should avoid anticholinergic and narcotic drugs, which may induce obstruction.

Definitive therapy is surgical. Although sexual potency and continence are usually retained, about 5 to 10% of patients will experience some postsurgical problems. Transurethral resection of the prostate (TURP) is preferred. Larger prostates (usually > 75 g) may require open surgery using the suprapubic or retropubic approach, permitting enucleation of the adenomatous tissue from within the surgical capsule. The incidence of impotence and incontinence is much higher than after TURP. All surgical methods require postoperative catheter drainage for 1 to 5 days. Alternative surgical approaches include intraurethral stents, microwave thermotherapy, high-intensity focused ultrasound thermotherapy, laser ablation, electrovaporization, and radiofrequency vaporization; their roles are not established.

Page Reviewed and/or Updated:

September 21, 2008