Prostate Diseases

Published on 16/04/2015 by admin

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Last modified 22/04/2025

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18 Prostate Diseases

Basic Anatomy

image

Pelvic Cavity, Bladder, and Prostate

Prostate Proper

• Largest accessory gland of the male genital tract
• Partly glandular, partly fibromuscular
• Glandular growth and maturation controlled by testosterone, which is converted to dihydrotestosterone (DHT) by 5-alpha reductase
• Peri-urethral transition zone of the parenchyma: <10% of the stroma
• Peripheral zone of the gland: ~70% of the normal gland
• Smooth musculature of the prostate: part of the involuntary sphincter of the bladder
• Normal: walnut sized, ~20 g
• 5 “traditional” lobes

image Anterior (isthmus): largely muscular, sphincteric (see later)
image Middle: lies between urethra and ejaculatory ducts
image Posterior (inferoposterior): posterior to urethra and ejaculatory ducts, palpable (see later)
image Left and right lateral: form the majority of the prostate

• Middle lobe: most common site of benign prostatic hyperplasia (BPH), process arising in the periurethral transitional zone
• Anatomical parts: base, apex, four surfaces

image Base: vesicular surface, related to the base of the bladder
image Apex: inferior point, related to superior fascia of the urogenital diaphragm
image Anterior surface: retropubic, with largely transverse musculature, forms a rhabdosphincter (hemisphincter)
image Posterior surface: triangular, rests on ampulla of the rectum, palpable
image Inferolateral surfaces: resting on levator ani muscles and fascia

• Supported anteriorly by puboprostatic ligaments, central portions of the pubococcygeus, part of the levator ani muscles (anterior pelvic diaphragm)
• Supported inferiorly by the urogenital diaphragm (transversus perinei muscle and fascia), through which the urethra passes
• Bulbourethral (Cowper’s) glands

image Lie inferior and adjacent to the prostatic apex, within the urogenital diaphragm
image Provide mucus secretion for penile urethra

Prostatic Capsule(s)

• Prostatic (true) capsule: thin, dense, fibrous connective tissue enclosing parenchyma and surrounded by—
• False capsule: prostatic sheath, derived from inferior, endopelvic fascia

image Sheath is continuous inferiorly with superior fascia of urogenital diaphragm.
image Posterior sheath is part of the rectovesical septum.

• Prostatic venous plexus lies between prostatic capsule and surrounding sheath.

Prostatic Ducts and Urethra

• Multiple small prostatic ductules penetrate wall of prostatic urethra.
• Seminal colliculus (verumontanum) in posterior urethral wall marks location of paired ejaculatory ducts draining ductus deferens and seminal vesicles.
• Prostatic utriculus: small midline invagination in dome of colliculus, marks remnant of embryonic male paramesonephric (müllerian) ducts (“male uterus”)
image

Nerves of Pelvic Viscera

Prostatic Innervation

• Bilateral nerves of the prostate come from sacral (inferior hypogastric) nerve plexus lying between sacrum and rectum.
• Fibers to and from the prostate travel in posterolateral neurovascular bundles with nervi erigentes (responsible for erection-related functions) and prostatic arteries.
• Pelvic parasympathetic efferents travel in pelvic splanchnic fibers (S2-S4, nervi erigentes) through pelvic plexus.
• Sympathetic postganglionic fibers come from inferior mesenteric ganglion via hypogastric and inferior hypogastric plexuses.
• Sensory fibers from gland and capsule travel with nervi erigentes through pelvic plexus to sacral (S2-S4) spinal ganglia.

Vessels and Lymphatics

image

Arteries and Veins of Pelvis, Male

Arterial Supply

• Prostatic arteries derive variably from internal iliac circulation bilaterally, including branches of inferior vesical, inferior rectal, and internal pudendal arteries.
• Approach prostate posteriorly, adjacent to nervi erigentes (neurovascular bundles) and prostatic nerve plexus in floor of pelvis

Venous Drainage

• Prostatic venous plexus lies around sides and anterior aspect of gland, between prostatic capsule and its surrounding prostatic sheath (fascia).
• Plexus drains into internal iliac veins via prostatic or inferior vesical branches.
• Plexus also drains posteriorly into vertebral venous plexuses (route for metastases).
image

Lymphatics of Prostate

Lymphatics

• Lymphatics of prostate drain into internal iliac and obturator (pelvic) nodes.
• Pelvic lymph nodes drain up into aortic chain of nodes.

Clinical Correlates

Prostate Specific Antigen (PSA)

• Normal patient, PSA < 4.0 ng/mL
• PSA increases seen in prostatitis, BPH, prostatic carcinoma, chronic catheterization (nonspecific)
• Prostate cancer may be detected when PSA surpasses 4.0 ng/mL: need for regular testing increases in at-risk men.
• Should return to undetectable level after prostatectomy, unless significant metastases exist

Benign Prostatic Hyperplasia (BPH)

Diagnosis

• Typically begins in transitional zone surrounding urethra
• Presenting symptoms (typical) are difficulty with urination: hesitancy, decrease in force, intermittency, increased frequency, nocturia, urinary retention
• Gradual onset, possible history of urinary tract infections (UTIs)
• Digital rectal exam (DRE) might demonstrate palpable enlargement.
• PSA level should be measured, although it is not specific.

Treatment

• Treatment decisions are based on level of difficulty experienced by the patient (goal-directed therapy).
• Medical treatment is first-line therapy: alpha blockers, 5-alpha reductase inhibitors (e.g., finasteride).
• Transurethral prostatectomy (TURP)

image Gold standard
image Indicated for recurrent UTIs, stones, gross hematuria, renal insufficiency, medical treatment failure

• Open prostatectomy

image Typically through a lower midline abdominal incision
image May be indicated for a patient with a particularly large prostate

Aspects of TURP

image

Transurethral Prostatectomy

• Post-TURP syndrome

image Hyponatremia secondary to irrigation
image Can precipitate seizures and cerebral edema

Carcinoma of the Prostate

• Most common male solid organ cancer in the U.S., currently the second most common cause of cancer mortality, with adenocarcinoma the most common type
• It manifests in different ways.

image Indolent course: asymptomatic, sometimes only discovered postmortem or on indicated testing
image Aggressive course: extracapsular spread with metastases and threat of early death

• The majority of men with low-grade prostate cancer have no symptoms.
• Most common site of primary carcinoma: posterior lobe
• Most common site of distal metastasis: bone, with osteoblastic lesions showing increased density on CT and radiograph
• Increases in serum alkaline phosphatase seen with extracapsular carcinoma and metastases
image

Prostatic Carcinoma

Staging and Treatment

• Tumor/node/metastasis (TNM) system used
• Gleason scoring system: additional scoring (1-5) from well-differentiated (least aggressive) to poorly differentiated (most aggressive)
• Transrectal ultrasonography (TRUS) can provide an accurate image of the gland and guide needle biopsies.
• CT can provide evidence of prostatic pathoanatomy, lymphadenopathy, and metastases.
• Optimal treatment for localized prostate cancer remains controversial.
• Intracapsular tumors, no metastases (on T1 and T2 MRI): irradiation, radical prostatectomy with pelvic lymph node excision, or no treatment depending on age, specifics
• Extracapsular tumors with metastases

image Hormonal treatment with luteinizing hormone–releasing hormone blocker or testosterone blockers, potential orchiectomy
image Irradiation for pain of bony metastases, chemotherapy for hormone-resistant disease

• “Chemical castration”: luteinizing hormone–releasing hormone (LHRH) antagonists suppress testosterone production in androgen-dependent tumors
• LHRH antagonists are also called GnRH antagonists (gonadotropin releasing hormone blockers).
• Alternatives or complements to prostatectomy: x-ray or particle beam therapy, brachytherapy (implanted radiation sources), and cryotherapy

Surgical Approaches in Prostatectomy

• Retropubic approach to radical (complete) prostatectomy: preferred for giving access to pelvic lymph nodes; venous bleeding risk
• Perineal approach to radical prostatectomy: requires second incision or laparoscopy for lymphadenectomy
image

Radical Prostatectomy

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