Diagnostic Ultrasound - Abdomen and Pelvis

Prostate
○ Sac-like structures superolateral to prostate, lateral
outpouchings of vas deferens
○ Secrete fructose-rich fluid (energy source for sperm)
○ Arterial supply: Vesiculodeferential artery (branch of
superior vesical artery)
– May have additional supply from inferior vesical artery
○ Venous drainage into pelvic venous plexus
○ Lymphatic drainage into external and internal iliac nodes
• Ejaculatory ducts
○ Located on either side of midline
○ Formed by union of seminal vesicle duct and vas
deferens
○ Start at base of prostate and run forward and downward
through gland in CZ
IMAGING ANATOMY
Prostate
• Transrectal ultrasound (TRUS)
○ Normal TZ is typically uniformly more echogenic than
inner gland
○ Inner gland (TZ and CZ) is often distinguishable from PZ
– Heterogeneous TZ in BPH
○ TRUS-guided biopsy generally recommended when
patient's PSA level is elevated or abnormal digital rectal
exam (DRE) (exception: When elevated PSA occurs with
suspected prostatitis → repeat PSA 2-3 months later)
– TRUS: Visual aid for systematic biopsy of entire
prostate, estimate prostate volume
– TRUS has become mainstay of many image-guided
prostate interventions: Prostate biopsy,
brachytherapy, cryotherapy, and high-intensity
focused ultrasonography (HIFU) as well as BPH
evaluation
• Prostate volume measurement
○ Prolate ellipse volume for 3 unequal axes:Width x height
x length x 0.523
○ 1 cc of prostate tissue ~ 1 g; prostate weighs ~ 20 g in
young men
○ Prostatic enlargement when gland is > 40 g
Seminal Vesicles and Vasa Deferentia
• Cystic appearance on TRUS, should be symmetric
ANATOMY IMAGING ISSUES
Imaging Recommendations
• Transducer
○ 7-10 MHz rectal transducer (end-firing or transverse
panoramic)
○ 3.5-6 MHz curved linear transducer for transabdominal
ultrasound
○ Perform in at least 2 orthogonal planes (axial and
sagittal)
• Patient position
○ TRUS: Left lateral decubitus with flexed hips and knees
or in lithotomy position
○ Transabdominal ultrasound: Supine, using urinary
bladder as acoustic window (transvesical)
– Fluid intake to ensure bladder distension
Imaging Pitfalls
• Abnormal vascularity on power Doppler ultrasound may be
seen in hypertrophy, inflammation, and cancer
○ Useful for directing biopsy
• Transabdominal ultrasound of prostate is limited to
evaluation of prostate size
Transrectal Biopsy of Prostate
• Most transrectal transducers have needle guidance system
• Periprostatic block with local anesthesia injected along
neurovascular bundles; may also use anesthetic gel and
intraprostatic injection of local anesthetic
• Complications
○ Common: Hematuria, hematochezia, and
hematospermia
○ Other: Acute prostatitis, UTI, sepsis
CLINICAL IMPLICATIONS
Function
• 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
Zonal Distribution of Prostatic Disease
• Prostate adenocarcinomas
○ 75% in PZ
○ 20% in TZ
○ 5% in CZ
• BPH: Nodular stromal and epithelial hyperplasia in
periurethral (preprostatic) glands and TZ
○ Compresses CZ and PZ
○ Can cause bladder outlet obstruction from urethral
compression &/or increased smooth muscle tone along
bladder neck, prostate, and urethra
Spread of Prostate Carcinoma
• Signs of extraprostatic extension of prostatic carcinoma
○ Asymmetry of NVB
○ Obliteration of rectoprostatic angle
○ Irregular bulge in prostatic contour
• Up to 80% of prostatic cancers in peripheral zone are
hypoechoic
SELECTED REFERENCES
1. Chung B, et al: Anatomy of the lower urinary tract and male genitalia. In
Campbell-Walsh Urology. 10th ed. Philadelphia: Saunders: 2012:33-70
2. Trabulsi E, et at: Ultrasonography and biopsy of the prostate. In Campbell-
Walsh Urology. 10th ed. Philadelphia: Saunders: 2012: 2735-2747
3. Hammerich K, et al: Anatomy of the prostate gland and surgical pathology of
prostate cancer. In Prostate Cancer. Cambridge, UK: Cambridge University
Press: 2009: 1-14
4. Boczko J et al: Transrectal sonography in prostate evaluation. Radiol Clin
North Am. 44(5):679-87, viii, 2006
5. McLaughlin PW et al: Functional anatomy of the prostate: implications for
treatment planning. Int J Radiat Oncol Biol Phys. 63(2):479-91, 2005
6. McNeal JE. The zonal anatomy of the prostate. Prostate. 2(1):35-49, 1981
Anatomy: Pelvis
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