Prostate

The prostate is a small, walnut-shaped gland located in the male pelvis, surrounding the prostatic urethra. It plays a crucial role in the male reproductive system by producing seminal fluid, which nourishes and transports sperm. Understanding the anatomy, physiology, and diseases of the prostate is essential for early diagnosis and effective management of prostate-related conditions.

Anatomy

Gross Anatomy

The prostate is situated below the urinary bladder and anterior to the rectum, encasing the prostatic urethra. It is typically described in terms of four zones:

• Peripheral Zone: Located posteriorly and is the most common site for prostate cancer.
• Central Zone: Surrounds the ejaculatory ducts and comprises approximately 25% of glandular tissue.
• Transitional Zone: Surrounds the urethra and is the primary site for benign prostatic hyperplasia.
• Anterior Fibromuscular Stroma: Non-glandular tissue that provides structural support.

Microscopic Anatomy

The prostate is composed of glandular and stromal components. The glandular tissue consists of acini lined by secretory and basal epithelial cells, which produce prostatic fluid. The stroma is made up of smooth muscle fibers, fibroblasts, and connective tissue that provide structural integrity and contractile function for expelling prostatic secretions into the urethra.

Vascular and Lymphatic Supply

• Arterial Supply: Primarily from the inferior vesical artery, a branch of the internal iliac artery.
• Venous Drainage: Through the prostatic venous plexus into the internal iliac veins.
• Lymphatic Drainage: Drains into the internal iliac, sacral, and obturator lymph nodes, which is important in the spread of malignancy.

Nervous Supply

• Autonomic Innervation: Sympathetic fibers from the hypogastric plexus regulate smooth muscle contraction.
• Somatic Innervation: Provides sensory feedback via the pelvic nerves.

Physiology

Secretory Function

The primary physiological role of the prostate is to produce and secrete prostatic fluid, which constitutes approximately 20-30% of the total semen volume. This fluid contains enzymes, citric acid, zinc, and prostaglandins that support sperm motility, viability, and fertilization capacity. During ejaculation, contraction of the prostatic smooth muscle helps expel semen into the urethra.

Hormonal Regulation

Prostate growth and function are tightly regulated by androgens, particularly dihydrotestosterone (DHT), a metabolite of testosterone. DHT binds to androgen receptors in prostatic epithelial and stromal cells, stimulating growth and secretory activity. Estrogens and other endocrine factors may also modulate prostatic development and cellular proliferation.

Development and Aging

Embryology

The prostate develops from the urogenital sinus under the influence of androgens during the 10th to 12th week of gestation. Epithelial buds invade the surrounding mesenchyme, forming the glandular structures, while the stroma differentiates into smooth muscle and connective tissue. Proper androgen signaling is essential for normal prostatic morphogenesis.

Pubertal Changes

During puberty, rising testosterone levels trigger prostatic growth and maturation. The gland increases in size, and secretory activity commences, contributing to the production of seminal fluid. These changes establish the functional capacity of the adult prostate.

Age-related Changes

• Benign Prostatic Hyperplasia (BPH): Age-related proliferation of glandular and stromal cells in the transitional zone, leading to urinary obstruction in older men.
• Atrophy and Fibrosis: Aging may also cause stromal fibrosis and glandular atrophy, altering prostate texture and volume.

Clinical Examination

Digital Rectal Examination (DRE)

Digital rectal examination is an essential component of prostate evaluation. The clinician palpates the posterior surface of the prostate through the rectal wall to assess size, shape, consistency, and the presence of nodules or induration. DRE helps detect abnormalities suggestive of benign prostatic hyperplasia, prostatitis, or prostate cancer.

Imaging Studies

• Transrectal Ultrasound (TRUS): Provides visualization of prostate size, internal architecture, and nodular lesions. It is also used to guide prostate biopsies.
• MRI and CT Scans: Multiparametric MRI is particularly useful for detecting clinically significant prostate cancer and evaluating local extension. CT scans are generally used for staging metastatic disease.

Prostate Diseases

Benign Prostatic Hyperplasia (BPH)

BPH is a common age-related condition characterized by proliferation of stromal and epithelial cells in the transitional zone. Clinical manifestations include urinary frequency, urgency, nocturia, weak stream, and incomplete bladder emptying. BPH does not predispose to prostate cancer but can significantly impact quality of life.

Prostatitis

• Acute Bacterial Prostatitis: Sudden onset of fever, dysuria, perineal pain, and urinary retention caused by bacterial infection.
• Chronic Bacterial Prostatitis: Persistent or recurrent urinary tract infections with lower urinary tract symptoms.
• Chronic Pelvic Pain Syndrome: Non-bacterial inflammation causing pelvic discomfort, urinary symptoms, and sexual dysfunction without identifiable infection.

Prostate Cancer

• Risk Factors: Age over 50, family history, African descent, and genetic mutations such as BRCA1/2.
• Pathophysiology: Malignant transformation of prostatic epithelial cells, often originating in the peripheral zone.
• Screening and Diagnosis: PSA testing, DRE, imaging, and confirmatory prostate biopsy.

Other Conditions

• Prostate abscess: Localized collection of pus, usually in the setting of bacterial infection.
• Cysts and calculi: Benign cysts or stones within the prostatic ducts or acini that may cause obstructive symptoms.

Diagnosis and Investigations

Laboratory Tests

• Prostate-Specific Antigen (PSA): A serum marker used to screen for prostate cancer and monitor disease progression or response to therapy. Elevated PSA levels may also occur in BPH and prostatitis.
• Urinalysis and Cultures: Useful in detecting bacterial infection in cases of prostatitis or urinary tract involvement.

Imaging Modalities

• Transrectal Ultrasound (TRUS): Provides detailed images of the prostate, measures volume, and identifies suspicious lesions.
• MRI and CT: Multiparametric MRI is preferred for detecting clinically significant prostate cancer, staging, and guiding targeted biopsies. CT is used for evaluating metastatic spread.

Histopathology

• Prostate Biopsy Techniques: Typically performed under TRUS guidance, with systematic or targeted sampling of suspicious areas.
• Histological Grading: The Gleason scoring system classifies prostate cancer based on glandular architecture and predicts aggressiveness.

Treatment and Management

Medical Management

• Alpha-blockers: Relax prostatic smooth muscle to improve urinary flow in BPH.
• 5-alpha Reductase Inhibitors: Reduce prostate volume by inhibiting conversion of testosterone to dihydrotestosterone.
• Antibiotics: Used for bacterial prostatitis, guided by urine culture results.

Surgical Interventions

• Transurethral Resection of the Prostate (TURP): Standard surgical procedure for relieving obstruction in BPH.
• Prostatectomy: Radical prostatectomy is performed for localized prostate cancer.
• Minimally Invasive Therapies: Techniques such as laser therapy, microwave therapy, and prostatic urethral lift provide alternative options for symptom relief.

Oncological Management

• Radiotherapy: External beam or brachytherapy for localized or locally advanced prostate cancer.
• Hormone Therapy: Androgen deprivation therapy to control disease progression in advanced cases.
• Chemotherapy: Used in metastatic or castration-resistant prostate cancer.

Prevention and Screening

Screening Guidelines

Screening for prostate diseases, particularly prostate cancer, is aimed at early detection to improve outcomes. Key methods include:

• PSA Testing: Recommended for men over 50 or earlier in high-risk groups such as those with a family history or African descent.
• Digital Rectal Examination (DRE): Performed alongside PSA testing to identify nodules, asymmetry, or induration suggestive of malignancy.

Risk Reduction Strategies

Lifestyle and preventive measures may reduce the risk of prostate-related conditions:

• Maintaining a healthy weight through diet and exercise.
• Consuming a diet rich in fruits, vegetables, and low in saturated fats.
• Avoiding smoking and limiting alcohol intake.
• Regular medical check-ups for early detection and monitoring.

Prognosis and Complications

Outcomes in BPH

With appropriate medical or surgical management, most men with BPH experience symptomatic relief and improved urinary function. Untreated cases may lead to urinary retention, recurrent infections, or bladder stones.

Prostate Cancer Prognosis

The prognosis depends on stage, grade, PSA level, and overall health. Localized prostate cancer has a favorable outcome with high survival rates, while metastatic disease carries a poorer prognosis and requires systemic therapy.

Complications of Prostate Diseases

• Urinary obstruction leading to bladder dysfunction or kidney damage.
• Recurrent urinary tract infections or prostatitis.
• Metastatic spread of prostate cancer to bones, lymph nodes, or other organs.

References

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