Walnut-sized gland beneath bladder and in front of rectum

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  Normal prostate in young male ~ 3-cm length x 4-cm width x 2-cm depth

Inverted conical shape

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  Base : Superior portion, continuous with bladder neck

  
  
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  Apex : Inferior portion, continuous with striated urinary sphincter

Main function is to add nutritional secretions to sperm to form semen during ejaculation

Also plays role in controlling flow of urine; prostate muscle fibers are under control of involuntary nervous system and contract to slow and stop urine

Urethra traverses prostate

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  Verumontanum midway between base and apex where urethra makes ~ 35° bend anteriorly

  
  
  
  
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    Openings of prostatic utricle and ejaculatory ducts

    
    
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    Divides prostatic urethra into proximal (preprostatic) and distal (prostatic) segments

  
  
  
  
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  Urethral crest : Narrow longitudinal ridge on posterior wall with small openings draining prostatic ducts

Neurovascular bundles

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  Lie posterolaterally to prostate at 5- and 7-o’clock positions

  
  
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  Carry nerves and vascular supply to corpora cavernosa of penis (necessary for normal erection)

Seminal vesicles

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  Sac-like structures superolateral to prostate

  
  
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  Secrete fructose-rich fluid (energy source for sperm)

Ejaculatory ducts located on either side of midline

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  Formed by union of seminal vesicle duct and vas deferens

  
  
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  Start at base of prostate and run forward and downward through gland to verumontanum

Prostate is histologically composed of ~ 70% glandular and 30% nonglandular elements

Central zone (CZ) : ~ 25% glandular tissue; cone-shaped zone around ejaculatory ducts with widest portion making majority of prostatic base

Peripheral zone (PZ) : ~ 70% glandular tissue, covers posterolateral aspects of gland

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  Surrounds CZ and distal prostatic urethra

  
  
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  Zone where cancer most commonly occurs

Transition zone (TZ) : 2 separate lobules surround urethra proximal to verumontanum

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  ~ 5-10% glandular tissue in young males; can be very large in older males with benign prostatic hypertrophy (BPH)

Anterior fibromuscular stroma is nonglandular tissue

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  Runs anteriorly from bladder neck to striated urinary sphincter

Prostate pseudocapsule (“surgical capsule”)

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  Visible boundary between TZ and PZ representing compressed tissue

  
  
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  Frequently, calcified corpora amylacea (laminated bodies formed of secretions and degenerate cells) highlight plane between PZ and TZ

Prostate adenocarcinomas

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  Up to 80% of prostatic cancers occur in PZ

  
  
  
  
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    Most appear as hypoechoic lesions

  
  
  
  
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  20% in TZ, 5% in CZ and are often indistinguishable from BPH

  
  
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  Signs of extraprostatic extension of prostatic carcinoma include asymmetry of neurovascular bundles and irregular bulge in prostatic contour

BPH : Benign nodular hyperplasia in periurethral glands and TZ

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  Can cause bladder outlet obstruction from urethral compression &/or increased smooth muscle tone along bladder neck and urethra

  
  
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  Compresses PZ posteriorly

  
  
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  Periurethral gland hypertrophy creates what has been termed median lobe , which can be seen projecting into bladder on transabdominal scans

Transabdominal ultrasound can assess size, but transrectal ultrasound (TRUS) is required for detailed assessment

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  Transducer

  
  
  
  
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    3.5- to 6.0-MHz curved transducer for transabdominal ultrasound

    
    
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    7- to 10-MHz rectal transducer (end firing or transverse panoramic)

  
  
  
  
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  Patient position

  
  
  
  
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    Transabdominal ultrasound: Supine, using urinary bladder as acoustic window (transvesical)

    
    
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    TRUS: Left lateral decubitus with flexed hips and knees or in lithotomy position

  
  
  
  
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  Transrectal biopsy of prostate

  
  
  
  
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    Transrectal transducers have needle guidance system

    
    
    
    
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      May be directed at lesion or in grid pattern covering prostate for random sampling

    
    
    
    
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    Complications include hematuria, hematochezia, hematospermia, and infection

  
  
  
  
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  Color/power Doppler nonspecific; may see increased flow in hypertrophy, inflammation, and cancer

  
  
  
  
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    Useful for directing biopsy

  
  

Normal PZ is typically uniformly more echogenic than inner gland

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  May be compressed in setting of BPH

TZ may appear heterogeneous and nodular in setting of BPH

Look for pseudocapsule (often with small calcifications) separating TZ from PZ

Seminal vesicles have cystic appearance on TRUS, should be symmetric

Prostate volume measurement

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  Perform in at least 2 orthogonal planes (axial and sagittal)

  
  
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  Prolate ellipse volume for 3 unequal axes: Width x height x length x 0.523

  
  
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  1 cc of prostate tissue weighs ~ 1 g; prostate weighs ~ 20 g in young men

  
  
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  Prostatic enlargement when gland is > 40 g