Prostate Anatomy and Pathology Study Notes

Prostate Anatomy and Physiology Study Notes

Prostate Overview

  • The prostate is a male reproductive gland that plays a key role in the production of seminal fluid.

Prostate Embryology

  • The prostate develops from epithelial outgrowths from the prostatic segment of the urethra, beginning at week 10 of embryonic development.

Prostate Location

  • The prostate's location is critical for its function and anatomy:
    • Retroperitoneal Gland
    • Inferior to the urinary bladder
    • Posterior to the symphysis pubis
    • Anterior to the rectum

Prostate Function

  • The prostate functions as an exocrine gland, which:
    • Secretes an alkaline milky substance comprising approximately 20 to 30% of semen.
    • The alkaline fluid is crucial as it helps sperm survive longer in the relatively acidic environment of the vagina.

Prostate Anatomy

General Structure

  • The prostate is considered to be about the size of a walnut, measuring approximately 4 x 2 x 3 cm.
  • The size of the prostate may vary with age, typically enlarging around the age of 40.
  • Shaped like an inverted rounded pyramid:
    • The base is the superior aspect (widest part) and rests against the inferior wall of the urinary bladder.
    • The apex is the inferior aspect (the narrowest part).

Zones of the Prostate

  • The prostate is divided into several distinct zones:
    1. Peripheral Zone (PZ)
    2. Central Zone (CZ)
    3. Transitional Zone (TZ)
    4. Anterior Fibromuscular Stroma (AFS)
Peripheral Zone (PZ)
  • Represents the outermost zone, comprising approximately 70% of the glandular tissue.
  • This zone is the most common location for malignancies.
Central Zone (CZ)
  • Encompasses about 25% of the prostate gland, surrounding the ejaculatory ducts.
  • Cancers in this zone are generally less common but tend to be more serious, with the potential for spreading to the seminal vesicles.
Transitional Zone (TZ)
  • The smallest zone surrounding the prostatic urethra (the segment passing through the prostate).
  • This zone is primarily responsible for the symptoms associated with an enlarged prostate.
Anterior Fibromuscular Stroma (AFS)
  • Composed of muscle and connective tissue (stroma).
  • Notably, the AFS does not contain any functional glandular tissues.

Blood Supply to the Prostate

Arterial Supply

  • Begins with the internal iliac artery which branches into:
    • Inferior vesical artery
    • The inferior vesical artery then divides into:
    • Prostatic Artery
    • Capsular Artery

Venous Drainage

  • The venous drainage system comprises many tiny veins that drain into the dorsal vein (which also drains the penis) and subsequently into the venous plexus, eventually leading to the internal iliac vein.

The Male Urethra

  • In males, the urethra performs two primary functions:
    • Excreting fluid waste (urine)
    • Excreting seminal fluid
  • The male urethra measures approximately 20 cm in length, extending from the bladder to the external orifice of the penis.
  • The female urethra is approximately 4 cm long, making females more susceptible to urinary tract infections (UTIs).

Segments of the Male Urethra

  1. Prostatic section
  2. Membranous section
  3. Spongy section
Prostatic Section
  • The most proximal portion of the urethra, measuring around 2.5 cm in length, extending from the neck of the urinary bladder to the mid-portion of the prostate.
  • Accepts drainage from small ducts within the prostate and from the ejaculatory ducts.
Membranous Section
  • The shortest section, measuring approximately 0.5 cm in length, running from the inferior aspect of the prostate to the proximal aspect of the penis.
Spongy Section
  • The longest section, measuring about 15 cm in length, extending the entire length of the penis to the external orifice.

Seminal Vesicles

  • The seminal vesicles are paired tubular hypoechoic structures located posteroinferior to the urinary bladder.
  • Each seminal vesicle measures approximately 4 – 5 cm in length and produces a fluid rich in sugars that nourishes and mixes with sperm to form semen.

Function of Seminal Vesicles

  • The produced fluid from the seminal vesicles empties into the ejaculatory ducts.
  • The ejaculatory ducts are formed by the fusion of the vas deferens (ductus deferens) and the seminal vesicle, surrounded by the central zone of the prostate.
  • The location where the ejaculatory duct meets the prostatic urethra is called the verumontanum.

Vas Deferens

  • The vas deferens, also known as the ductus deferens, is a muscular tube originating from the epididymis that travels superiorly into the pelvic cavity, terminating behind the urinary bladder.
  • Near its terminus, it becomes expanded into a section called the ampulla. It narrows again just outside the prostate, where it combines with the seminal vesicle to form the ejaculatory duct.

Function of Vas Deferens

  • The vas deferens transports mature sperm from the epididymis, playing a crucial role in the ejaculation process as sperm is propelled into the prostatic urethra and out of the penis during ejaculation.

Seminal Fluid Composition

  • Semen comprises fluids from:
    • Epididymis
    • Seminal vesicles
    • Prostate gland
    • Vas deferens
  • These fluids work collaboratively to nourish, protect, and assist in the motility of sperm towards the ovum.

Imaging Techniques for Prostate

Transabdominal Imaging

  • A full urinary bladder is required for transabdominal imaging, with the patient positioned supine. Proper draping techniques should be utilized while the ultrasound probe is angled approximately 30 degrees caudal using the bladder as a window.
  • Slight compression may be necessary to visualize the inferior portion of the prostate clearly.

Measurements for Prostate Volume

  • Prostate volume is a critical measurement, requiring three dimensions: height, width, and length.
  • These measurements are taken as follows:
    • Two in the sagittal scan plane
    • One in the transverse scan plane
  • Additionally, the urinary bladder should also be imaged for volume pre- and post-void stages.

Transrectal Imaging (TRUS)

  • In transrectal imaging, the patient is positioned in a lateral decubitus position facing away from the sonographer with knees bent towards the chest. Adequate gel is required for optimal probe insertion, and a small amount of urine in the bladder aids identification.
  • The prostate is visualized in sagittal and transverse planes, and volume measurements are similar to those outlined in transabdominal imaging.

Prostate Pathology

Prostate-Specific Antigen (PSA)

  • Prostate-Specific Antigen (PSA) is a protein produced by the prostate, and its levels are measured via a blood test.
  • Elevated PSA can indicate various prostate conditions, such as:
    • Benign Prostatic Hyperplasia (BPH)
    • Prostate Cancer
    • Prostatitis

Normal PSA Range by Age

  • Ranges for PSA increase as men age:
    • Under 50: PSA < 2.5 ng/ml
    • 50-59: PSA < 3.5 ng/ml
    • 60-69: PSA < 4.5 ng/ml
    • Over 70: PSA < 6.5 ng/ml

Benign Prostatic Hyperplasia (BPH)

  • BPH refers to a non-malignant enlargement of the prostate gland, which is common as men age. Characterized by an increase in the number of normal cells within prostate tissue.
Diagnosis of BPH
  • Detection methods include:
    • Digital Rectal Exam: Used to detect prostate enlargement.
    • Blood Test: Elevated PSA from increased prostate cells.
    • Cystoscopy: Examination of the urethra, bladder, and prostate.
    • Ultrasound Examination: Including TRUS or transabdominal imaging.
    • Biopsy: Commonly performed via transrectal ultrasound-guided procedure.

Clinical Symptoms of BPH

  • BPH generally manifests with symptoms post age 50, including:
    • Urinary frequency
    • Nocturia
    • Urinary urgency
    • Weak urinary flow
    • Dysuria (painful urination)

Complications of BPH

  • More serious complications can involve:
    • Urinary Stasis
    • Urinary Tract Infections
    • Complete blockage of the urethra
    • Renal Infection
    • Renal Failure

Sonographic Findings in BPH

  • Common observations may include:
    • Enlarged prostate gland
    • Possible cysts
    • Heterogeneous echotexture
    • Possible post-void residual
    • Possible calcifications

Prostatitis

  • Prostatitis can be classified as:
    1. Acute bacterial
    2. Chronic bacterial
    3. Prostatodynia (non-bacterial, idiopathic)
    4. Asymptomatic inflammatory

Clinical Symptoms of Prostatitis

  • Symptoms can include:
    • Painful and/or frequent urination
    • Hematuria (blood in urine)
    • Groin pain
    • Fever
    • Body aches
    • Penile discharge

Prostate Cancer

  • Prostate cancer is the most frequently diagnosed cancer in men (aside from skin cancer), although only 1 in 41 men may die from it.
  • Treatment protocols can involve:
    • Surgery
    • Radiation
    • Hormonal therapy
    • Chemotherapy
    • Watchful waiting for some men.

Risk Factors for Prostate Cancer

  • The most prevalent type is adenocarcinoma, commonly found in:
    • African American males over the age of 50.
    • Tumors typically arise in the peripheral zone (PZ).

Clinical Symptoms of Prostate Cancer

  • Prostate cancer may often present with no symptoms, but potential early signs can include:
    • Frequent urination, especially at night
    • Pain in lower back, hips, or upper thighs
    • Difficulty having erections
    • Blood in urine or semen

Sonographic Findings in Prostate Cancer

  • Imaging may reveal:
    • Enlarged prostate
    • Hypoechoic mass
    • Possible calcifications
    • Hypervascularity

Treatment for Malignancy

  • The following treatments are available for prostate malignancy:
    • Radiation Therapy
    • Brachytherapy
    • Chemotherapy
    • Cryosurgery
    • Hormonal Therapy
    • HIFU (High-Intensity Focused Ultrasound)
    • Radical Prostatectomy
    • Potential pitfalls can involve incontinence and impotence.

Ultrasound Guided Prostate Biopsy

  • A biopsy involves using a fine needle to obtain samples of potentially cancerous tissue from the prostate.
  • Prepared with:
    • An 18-gauge core biopsy gun
    • A 25-gauge needle for lidocaine administration (about 10 cc) prior to the procedure.

Patient Preparation for Biopsy

  • Preparation steps include:
    • Stopping medications that might increase bleeding several days before the procedure.
    • Performing a cleansing enema at home prior to the appointment.
    • Administering antibiotics 30 to 60 minutes before to reduce the risk of infection.

Patient Positioning for Biopsy

  • The patient is typically placed in a lateral decubitus position, facing away from the ultrasound machine, with knees bent towards the chest.
  • Expected outcomes post-procedure may include bleeding and discomfort, with recommendations for rest and limited activity thereafter.

Sample Collection

  • Generally, 6 to 12 tissue samples are taken from the prostate during the procedure and sent to the lab for analysis.

Metastases

  • Prostate cancer may metastasize in several ways:
    • Bone: Commonly spreading to the spine.
    • Lymphatic: Pathways that lead to other organs.
    • Direct Invasion: Possible spread to the rectum and bladder.

Penile Anatomy and Conditions

Penile Ultrasound

  • Penile ultrasound examines various conditions affecting the penis, such as:
    • Erectile dysfunction (ED)
    • Fibrosis
    • Tumors

Erectile Dysfunction

  • Men experiencing erection difficulties often undergo a Doppler ultrasound to evaluate blood flow functionality, aiming to identify potential problems with arterial dilation or venous constriction.
  • The Doppler exam involves the administration of a medicinal injection to prompt arterial dilation and increased blood flow.

Penile Fracture

  • Defined as a tear in the tunica albuginea, which could occur during vigorous intercourse and constitutes a medical emergency due to potential complications like erectile dysfunction.
  • Surgical intervention is the primary treatment, and specific diagnostic imaging is utilized to assess for additional urethral damage.

Tumors of the Penis

  • Although penile tumors constitute less than 1% of male cancers, poor hygiene is the key etiologic factor, primarily in uncircumcised males.
  • Squamous cell carcinoma comprises the majority of penile cancers, commonly presenting on the glans, with the appearance varying from papillary to ulcerative.

Summary of Clinical Correlations

  • Male circumcision reduces the likelihood of developing penile carcinoma.
  • Recognizing symptoms and appropriate imaging is vital for diagnosis and treatment management for prostate and related pathologies.