Benign Prostatic Hyperplasia

Introduction

Benign prostatic hyperplasia is a non-malignant increase in the number of epithelial and stromal cells of the prostate, occurring specifically in the transitional zone that surrounds the prostatic urethra. As the gland enlarges it compresses the urethra, producing bladder outlet obstruction and the constellation of lower urinary tract symptoms (LUTS) that brings men to medical attention.¹

It is one of the commonest conditions of ageing men: histological BPH is present in around 50% of men in their 60s and 80-90% of men over 80, though only a proportion have troublesome symptoms. The development of BPH requires both ageing and the presence of testosterone - men castrated before puberty do not develop it, which is the basis of hormonal treatment.

Pathophysiology and risk factors

Within the prostate, testosterone is converted by the enzyme 5-alpha reductase into dihydrotestosterone (DHT), which is considerably more potent and is the principal driver of prostatic growth. This is precisely the step blocked by finasteride and dutasteride.

Obstruction has two components, which is why two different drug classes are used:

• A static component - the physical bulk of the enlarged gland. Treated by 5-alpha reductase inhibitors, which reduce prostate volume by around 20-30% over months
• A dynamic component - smooth muscle tone in the prostate and bladder neck, mediated by alpha-1 adrenoceptors. Treated by alpha-blockers, which act within days

The bladder responds to chronic outflow obstruction with detrusor hypertrophy and trabeculation, producing detrusor overactivity and the storage symptoms of frequency, urgency and nocturia. If obstruction persists, the detrusor eventually decompensates, leading to incomplete emptying, chronic retention and, in high-pressure retention, hydronephrosis and renal impairment.

Risk factors

• Increasing age - the dominant factor
• Functioning testes and androgens - BPH does not occur without them
• Family history of BPH
• Obesity, metabolic syndrome and type 2 diabetes
• Ethnicity - higher rates reported in Black men and lower rates in men of East Asian origin
• Sedentary lifestyle; physical activity appears protective

Clinical features

Symptoms are conventionally divided into voiding (obstructive) and storage (irritative) groups. Most men have a mixture, and it is worth noting explicitly that LUTS is a syndrome, not a diagnosis - BPH is only one of its causes.

Scoring severity

The International Prostate Symptom Score (IPSS) is the standard tool. It comprises seven symptom questions scored 0-5 plus a quality-of-life question, giving a total out of 35:

• 0-7: mild - usually managed with watchful waiting and lifestyle advice
• 8-19: moderate
• 20-35: severe
• The quality-of-life question is arguably the most important, because the decision to treat is driven by bother rather than by the score alone - a man with moderate symptoms who is not troubled may need no treatment, while one with mild symptoms and severe nocturia may want it

Examination

• Abdominal examination - for a palpable bladder indicating retention
• Digital rectal examination - the key examination. A benign prostate is smooth, firm, symmetrical, with a palpable median sulcus and typically non-tender. Hard, craggy, nodular, asymmetrical, fixed, or with loss of the median sulcus suggests malignancy. A tender, boggy prostate suggests prostatitis
• External genitalia - phimosis, meatal stenosis
• Focused neurological examination - where a neurogenic bladder is a possibility
• Note that prostate size on DRE correlates poorly with symptom severity, though it does influence drug choice

Differential diagnosis

Investigations

• IPSS questionnaire - to quantify symptoms and bother at baseline and to monitor response
• Urine dipstick and culture - to exclude infection, haematuria and glycosuria
• Bladder diary (frequency-volume chart) for at least 3 days - distinguishes true LUTS from polyuria and from nocturnal polyuria, which are managed quite differently
• U&Es and creatinine - to detect obstructive renal impairment, particularly important if there is a large residual volume
• Post-void residual volume by bladder scan - identifies incomplete emptying and chronic retention
• PSA - see the caution below
• Urinary flow rate (uroflowmetry) - a maximum flow rate (Qmax) under 10 mL/s suggests obstruction; used in secondary care
• Renal tract ultrasound - if there is renal impairment, a large residual, haematuria, recurrent infection or suspected stones, to look for hydronephrosis
• Transrectal ultrasound and prostate volume measurement - to guide the choice of drug and surgical approach
• Multiparametric MRI and prostate biopsy - where prostate cancer is suspected
• Urodynamic studies - before surgery where the diagnosis is uncertain or a neurogenic cause is possible
• Flexible cystoscopy - for haematuria, suspected stricture, stone or bladder tumour

Management

Treatment is guided by how bothersome the symptoms are and by the presence of complications, following NICE CG97.¹ Many men need no treatment at all.

Conservative management

Watchful waiting with lifestyle advice is appropriate for mild symptoms (IPSS 0-7) or symptoms that are not bothersome.

• Reduce evening fluid intake, and reduce caffeine and alcohol, both of which are diuretic and bladder irritants
• Double voiding - waiting and voiding a second time to improve emptying
• Bladder training for storage symptoms
• Treat constipation
• Review medications - diuretics, anticholinergics, opioids, antihistamines, tricyclics and decongestants all worsen symptoms
• Containment products and urinary sheaths as an adjunct where appropriate

Medical management

Surgical management

Surgery is indicated for failure of or intolerance to medical therapy, and for complications: recurrent acute retention, high-pressure chronic retention with renal impairment, recurrent urinary tract infection, bladder stones, or recurrent haematuria from the prostate.

• Transurethral resection of the prostate (TURP) - the long-standing standard operation; endoscopic resection of transitional zone tissue
• Transurethral incision of the prostate (TUIP) - for smaller glands; lower risk of retrograde ejaculation
• Holmium laser enucleation (HoLEP) and photoselective vaporisation - increasingly used, with less bleeding and shorter catheter times, and suitable for larger glands
• Prostatic urethral lift (UroLift) and water vapour therapy (Rezum) - minimally invasive options that preserve ejaculatory function, suitable for selected men
• Open or robotic simple prostatectomy - for very large glands
• Prostatic artery embolisation - an option in selected patients unfit for surgery

Complications

• Acute urinary retention - painful, requiring catheterisation; a common presentation of undiagnosed BPH
• Chronic urinary retention, and in particular high-pressure chronic retention with bilateral hydronephrosis and renal impairment
• Obstructive uropathy, acute kidney injury and chronic kidney disease
• Recurrent urinary tract infections from incomplete emptying and stasis
• Bladder calculi - from chronic stasis
• Bladder diverticula and detrusor decompensation - a chronically obstructed bladder may never regain effective contraction
• Overflow incontinence and nocturnal enuresis
• Haematuria - from friable enlarged prostatic vessels
• Falls and sleep disturbance from nocturia, and considerable impairment of quality of life
• Complications of treatment - postural hypotension and falls from alpha-blockers, sexual dysfunction from 5-alpha reductase inhibitors, and the surgical complications above

Red flags

Prognosis

BPH is a chronic, slowly progressive condition, but its course is highly variable. A substantial proportion of men have symptoms that remain stable or even improve spontaneously over years, which is why watchful waiting is a legitimate and often successful strategy for mild or non-bothersome symptoms rather than a way of avoiding treatment.

Medical therapy is effective for most men who need it. Alpha-blockers improve symptom scores within days and are effective regardless of prostate size, while 5-alpha reductase inhibitors additionally alter the natural history - they reduce prostate volume and lower the long-term risk of acute urinary retention and the need for surgery by around half in men with enlarged glands. Combination therapy is more effective than either agent alone for preventing progression, at the cost of more adverse effects.

Surgery gives the greatest and most durable symptomatic improvement, with TURP producing substantial reductions in IPSS and improvements in flow rate that are maintained for years; around 10% require repeat surgery within a decade as tissue regrows. The important caveat is that outcomes are considerably worse where the detrusor has already decompensated after prolonged obstruction - such men may continue to empty poorly and remain dependent on catheterisation even after a technically successful operation. This is the strongest argument for identifying chronic retention and renal impairment early, and it is why a bladder scan and a creatinine matter as much as the symptom score.