BPH: Etiology - Epidemiology
There is no globally accepted epidemiologic definition of BPH.
Benign prostatic hyperplasia (BPH) refers to a regional nodular growth of varying combinations of glandular and stromal proliferation that occurs in almost all men who have testes and who live long enough.
Benign prostatic hyperplasia (BPH) is a pathologic process that contributes to, but is not the sole cause of, lower urinary tract symptoms (LUTS) in aging men.
The etiology of prostatic growth in older men have not been established.
A significant portion of LUTS is due to age-related detrusor dysfunction and other conditions such as polyuria, sleep disorders, and a variety of systemic medical conditions unrelated to the prostate-bladder unit.
Histopathologically BPH is characterized by an increased number of epithelial and stromal cells in the periurethral area of the prostate and referred to as hyperplasia.
It involves hyperplasia of prostatic stromal and epithelial cells, resulting in the formation of large, fairly discrete nodules in the periurethral region of the prostate.
When sufficiently large, the nodules compress the urethral canal to cause partial, or sometimes virtually complete, obstruction of the urethra, which interferes with the normal flow of urine.
It leads to symptoms of urinary hesitancy, frequent urination, dysuria (painful urination), increased risk of urinary tract infections, and urinary retention.
The hyperplasia results in a remodeling of the normal prostatic architecture.
Microscopic BPH refers to the histologic evidence of cellular proliferation
Histopathologically BPH is characterized by an increased number of epithelial and stromal cells in the periurethral area of the prostat
The molecular etiology of is uncertain.
The incidence of histologic or microscopic BPH is far greater than that of clinical or macroscopic BPH.
Macroscopic BPH refers to organ enlargement due to the cellular changes.
Epithelial budding from preexisting ducts and the appearance of mesenchymal nodules characterize the early stages of the process, but the tissue phenotype of patients with established disease is highly variable.
The development of BPH requires an intact androgen signaling pathway.
In the absence of obvious cellular proliferation, the hyperplastic process must be due to an imbalance between cell death and cell proliferation, leading to cell accumulation in both the epithelial and stromal compartments.
BPH stroma is a complex mixture of smooth muscle cells and extracellular matrix.
BPH is said to be a “stromal disease,” but it remains unclear whether the initiating events occur in the stromal compartment, the epithelial compartment, or both.
Paracrine and autocrine growth factors seem to be the primary factors that stimulate or inhibit stromal and epithelial growth.
Inflammation, common in BPH specimens, may play a role in the pathogenesis of the disease through cytokines that promote cell growth or lead to smooth muscle contraction.
BPH can have a familial inheritance.
The bladder's response to obstruction is only partially adaptive.
Smooth muscle cells subjected to increased load undergo hypertrophy, but the phenotype of the cell changes, ECM production is increased, contractile protein expression is altered, and cell-to-cell signaling is impaired.
Aging, perhaps through vascular mechanisms, leads to further alteration in bladder biology that in all likelihood amplifies the effects of obstruction.
Prostate growth is only one component of LUTS in aging men.
There is also significant contributions of aging, bladder dysfunction, nervous system changes, and systemic disease that in many cases has more impact on symptoms than the size of the prostate.
There is a clear trend toward an increase in symptom scores with advancing age.
When evaluating elderly men, one can therefore stratify them by the level of LUTS into mildly, moderately, and severely symptomatic according to a standardized symptom severity and frequency questionnaire.
The same patients then can be further classified based on the degree of prostatic enlargement as measured by digital rectal examination (DRE), transrectal ultrasonography (TRUS), or magnetic resonance imaging (MRI) and lastly by the presence and degree of bladder outlet obstruction as measured by flow rate recordings or invasive pressure flow studies.
There are several key baseline parameters allowing a stratification of patients according to the risk of progression. Age, symptom severity, flow rate, prostate size, and serum PSA are useful predictors of the risk of progression.
All relevant parameters such as symptom severity and frequency, bother, interference, disease-specific HRQOL, maximum flow rate, and prostate volume tend to worsen with advancing age.
Strong correlations exist between measures of symptom severity and frequency (IPSS), bother, disease-specific HRQOL, and interference scores.
There is a worsening of LUTS and BPH with time.
The two most significant progression events are acute urinary retention and the need for BPH-related surgery.
Although not exceedingly common, there is a significant baseline incidence rate and the risk is cumulative; that is, with increasing time of observation the incidence rate increases linearly.
The risk of acute urinary retention and need for surgery is to some degree predictable from baseline parameters with advancing age, increased prostate size, and higher serum PSA levels representing the most significant risk factors.
Benign prostatic hyperplasia symptoms are classified as storage or voiding.
Storage symptoms include urinary frequency, urgency (compelling need to void that cannot be deferred), urgency incontinence, and voiding at night (nocturia).
Voiding symptoms include urinary stream, hesitancy (needing to wait for the stream to begin), intermittency (when the stream starts and stops intermittently), straining to void, and dribbling.
Pain and dysuria are usually not present.
These storage and voiding symptoms are evaluated using the International Prostate Symptom Score (IPSS) questionnaire, designed to assess the severity of BPH.
Clinical BPH refers to the lower urinary tract symptoms thought related to benign prostatic obstruction.
Although LUTS due to BPH are generally progressive over time, spontaneous improvement can occur in an untreated patient, and thus the course may be highly variable.
Over a 1- to 5-year period, approximately 18 to 32 percent of patients with clinical BPH will experience subjective improvement,15 to 52 percent will have no change,16 to 60 percent will experience a worsening in their symptomatology.
Although BPH is rarely life-threatening, it is generally considered to be a slowly progressive disease.
BPH synonyms:
- Hyperplasia
- Benign prostatic hypertrophy
- Adenomatous hypertrophy
- Glandular hyperplasia
- Stromal hyperplasia.
References
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