|History: A few US images of the prostate.|
Diagnostic indications include the following:
|Discussion: The adult prostate is a chestnut-shaped organ enveloped in a fibrous capsule. The base of the prostate is attached to the bladder neck, and the apex is fixed to the urogenital diaphragm. |
The prostatic urethra traverses the gland. The verumontanum is a longitudinal ridge in the prostatic apex on which the ejaculatory ducts open.
The prostate is related superiorly and posteriorly to the seminal vesicles.
The ampullae of the vas deferens run medial to the seminal vesicles along the posterior surface of the prostate.
Anteriorly, the fibrous capsule thickens at the level of the apex to form puboprostatic ligaments, which attach the prostate to the back of the symphysis pubis.
According to the classic work by McNeal, the prostatic urethra is the main reference point of the prostate that divides the gland into an anterior fibromuscular stroma and a posterior glandular organ. The urethra angulates 35° anteriorly in the proximal portion of the prostate. The ejaculatory ducts run in the same plane as the distal prostatic urethra to join the verumontanum. Lowsley's concept of a 5-lobed prostate has been replaced by McNeal's concept of zonal architecture.
The prostate has 4 glandular zones, each with their own ductal system. The peripheral zone, transition zone, and periurethral glands have similar histological appearance and are derived from the urogenital sinus. However, the central zone is histologically distinct and is derived from mesonephric tissues (ie, wolffian tissue).
The peripheral zone constitutes almost 75% of the normal prostate gland. It occupies the distal prostate gland, the area around the urethra distal to the verumontanum. The central zone constitutes 25% of the normal prostate and occupies the part of the prostate behind the proximal prostatic urethra. Approximately 5-10% of the normal prostate gland is transition zone. The transition zone lies on either side of the proximal prostatic urethra lateral to the internal sphincter.
Biopsies are best performed with a spring-driven needle core biopsy device (or biopsy gun), which can be passed through the needle guide attached to the ultrasound probe. Most instrumentation provides optimal visualization of the biopsy needle path in the sagittal plane. In general, 18-gauge needles are used, and the tips of the needles are etched with small ridges or pits to render them more echogenic. Ultrasound images should be superimposed with a ruled puncture trajectory that corresponds to the needle guide of the probe, which allows anticipation of the needle path.
The procedure is usually performed on an out-patient basis. Because of the high risk of infection prophylactic
antibiotic administration is used routinely. Different antibiotic regimens have been described. Oral antibiotics
are inexpensive, well-tolerated and effective in reducing the incidence of urinary tract infections and fever.14
The regimen we use in our institution is Ciprofloxacin 500 mg orally half an hour before the procedure and 500mg
bd for the subsequent three days. A self-administered enema on the same day of the examination facilitates visualization in a clean field although this is not routinely used.
How I do it:Ultrasound-guided transrectal biopsy of the prostate
CME Radiology 2001; 2(3):134-138
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Case Number: 10885682Last Updated: 09-16-2007 The reader is fully responsible for confirming the accuracy of this content.