PATHOPHYSIOLOGY OF BPH

Introduction

Benign prostatic hyperplasia (BPH) is a very common urological problem seen locally and it is estimated that approximately 20% of men above t he age of 50 years might require treatment. Patient with BPH present with both obstructive and irritative symptoms. Obstructive symptoms include hesitancy, poor stream, post micturition dribbling and retention of urine. Irritative symptoms include frequency, dysuria, urgency and nocturia. About 50% of our local patients with BPH will have an enlarged prostate gland. However, the size of the prostate gland bears no relationship with severity of obstruction.


Etiology

The exact etiology of BPH is still poorly understood. Various risk factors have been implicated such as racial predilection, hypertension, liver cirrhosis and vasectomy but none had been proven convincingly. Studies and observations have shown that both increasing age and intact testes are important for BPH to develop as castration in young age of the development of BPH later in life.

Microscopic BPH starts to develop as early as in the thirties but clinical BPH usually present after the fifties. Studies of the various populations form different parts of the world have shown that t he incidence of the disease is approximately the same amongst the various races.


Anatomy of the Prostate Gland

Prostate gland is para reproductive organ of the male derives from the outpouching of the urethra during early embryonic life. It weighs about 15 grams in adults and is situated deep in the pelvis between the bladder and the external sphincter. It is an organ, which consists of both glandular epithelium and fibromuscular stroma with numerous ducts emptying into the prostatic urethra. Alkaline secretion is produced during sexual stimulation by these glands. Two zones or prostate gland are recognized on histological examination, the outer or the peripheral zone and the inner or the central zone.

Pathology and Pathogenesis of BPH

With increasing age, the prostate gland undergoes benign enlargement first around the prostatic urethra and later extends to involve the central zone. The weight of prostate gland in BPH is usually tow to three times that of normal. Grossly, nodular enlargements are seen in the prostate gland usually with cystic spaces due to dilatation of the obstructed prostatic ducts.

Histologically, hyperplasia of both glandular and fibromuscular components are seen in BPH. It is also important to note that with advancing age, carcinoma of the prostate gland is also likely to occur and this commonly arise from the peripheral zone. Both conditions present with symptoms of bladder outlet obstruction and can sometimes coexist.

The pathogenesis of BPH is still largely unresolved. Several theories have been postulated to explain it s development. These include: 1. Hormonal mechanism, an increase in the level of dihydro testosterone (DHT) in the cells leads to stimulation of cell growth. DHT is derived from testosterone by the enzymatic action of 5 alpha reeducates 2. Stem cell theory, by reactivation of the stem cells and benign enlargement of the prostatic gland 3. Stroma-epithelial interaction by growth factor which stimulates cell proliferation.

Both mechanical enlargement of the prostate gland as well as an increase in the tone of the prostatic urethra causes bladder outlet obstruction in BPH. The tone of the prostatic urethra is regulated by smooth muscle which is innervated buy the alpha adrenergic nerve fibres which are abundant in the prostate gland as well as in t he bladder neck.

Sequelae of BPH

Bladder outlet obstruction causes hypertrophy of the detrusor muscle and thickening of t he bladder due to increasing workload against the outflow resistance. Normal person empties the bladder with a detrusor pressure below 30 cm H20 with a maximal peak flow rate of more than 25 cc/sec. In the early phase of bladder outlet obstruction, the flow rate is maintained with increase in the emptying pressure. This is known as compensatory hypertrophy. As the obstruction progresses, the detrusor pressure rises further and the flow rate decreases with large amount of residual urine in the bladder, The detrusor muscle is replaced by fibrous tissue and become floppy with poor tonicity. This late phase is known as decompensatory hypertrophy and t he bladder is now suffering from irreversible damages.

In addition to thickening of the bladder wall, the increased detrusor pressure also leads to trabeculation, saccule and diverticulum formation in the bladder. When the obstruction is not relieved by appropriate treatment, hydronephrosis, hydroureter and renal failure can occur. As a result of increased residual urine, stasis can lead to stone formation in the bladder and is seen in about 10% of patients with BPH locally. Infection is also commonly seen at this stage and would be difficult to eradicate until obstruction is relieved. About 3-5% of patients with BPH present with chronic retention and overflow incontinence is usually associated with impairment of renal function. The response to treatment by TURP at this stage tends to be less satisfactory due to decompensation and is also associated with higher morbidity. Hence, to achieve optimal result of treatment for patient with BPH, timely intervention is important.

 

Natural History of BPH

The symptom of BPH varies depending on the severity of obstruction. Though t he symptoms generally progress with time, they do wax and wane along its course. Studies have showed that about 25 to 30% of patients experience improvement in their symptoms without treatment. Hence, strict objective criteria are needed in evaluating newer treatment modalities for patients with BPH.

Those with severe symptoms and associated with complications such as retention of urine, infection and renal impairment would require surgical treatment.

 

Conclusion

BPH is a common problem affecting the elderly male in our local population. It exact etiologies still poorly understood but aging, dihydrostestostrone, growth factor and epithelial – stroma interaction are believed to play an important role in its development. Obstruction in BPH is contributed both mechanical and neurogenic factors and surgical treatment is needed only in those with proven obstruction. With availability of newer medications and less invasive modalities of treatment, both physicians and urologists are now in a better position to tailor the choice of treatment according to the severity of the obstruction.