CHAPTER 121 Prostate and Seminal Vesicle Ultrasonography and Biopsy

Transrectal ultrasonography of the prostate (TRUSP) and seminal vesicles (SVs) is an essential tool in the assessment of these organs. Useful for defining anatomy, evaluating blood flow, and diagnosing and treating benign and malignant diseases of these glands, it is now the standard in most urologists’ practices.

Although TRUSP-SV has proved helpful in the investigation of the infertile couple, more importantly, the introduction of TRUSP-SV has improved the accuracy of prostate tissue sampling. Even though a digital rectal examination (DRE)–guided fine-needle or core (e.g., Tru-Cut, Biopty) biopsy may confirm cancer, it is not as useful for excluding cancer; DRE is more helpful for guiding biopsy of a palpable nodule. TRUSP-SV improves the ability of the clinician to exclude cancer in more regions of the gland and has somewhat become the standard for evaluation of possible prostate cancer.

One important recent development for TRUSP-SV, especially for underserved areas, is that technicians or sonographers are now making services available on-site for primary care clinicians, even to guide biopsy. Overreading services for TRUSP-SV by a radiologist are also now available over the Internet (see the “Suppliers” section). This may revolutionize the management of suspected prostate cancer. However, an understanding of anatomy is necessary before scanning or biopsy. The prostate can be described by its general, vascular, zonal, tissue, or ultrasonographic anatomy.

Although recent large studies in the United States and Europe have failed to clarify whether men benefit from screening for prostate cancer, most organizations are now recommending at least a discussion of this topic with their clinician, especially in men younger than 75 years of age and with at least a 10-year life expectancy. A prostate biopsy may be indicated if the examination or laboratory result is suspect for cancer (Fig. 121-1). Although certain ethnic groups (e.g., African Americans) were thought to be at increased risk of prostate cancer in the past, more contemporary analyses suggest that this discrepancy is disappearing. Much of any remaining variation may be more strongly related to education, insurance status, and access to health care.

Figure 121-1 Sample algorithm for men who desire early cancer detection after discussion of pros and cons with their clinician. DRE, digital rectal examination; PSA, prostate-specific antigen; TRUSP-SV, transrectal ultrasonography of the prostate and seminal vesicles. Contemporary analyses of African American men suggest that ethnic discrepancies are disappearing. Much of any ethnic variation still noted may be more strongly related to education, insurance status, and access to health care rather than ethnicity.

(Redrawn from Braunwald E, Fauci AS, Kasper DL, et al. [eds]: Harrison’s Principles of Internal Medicine, 15th ed. New York, McGraw-Hill, 2001.)

General Anatomy

Figure 121-2 shows the general anatomy of the prostate and seminal vesicles.

Figure 121-2 General anatomy of prostate and seminal vesicles.

(From Brooks JD: Anatomy of the lower urinary tract and male genitalia. In Walsh PC, Retik AB, Vaughan ED Jr, Wein AJ [eds]: Campbell’s Urology, 7th ed. Philadelphia, WB Saunders, 1998, pp 112–117.)

Prostate

The prostate is a chestnut-shaped gland surrounded by a pseudocapsule of dense fibrous tissue and smooth muscle that connects with the muscular layers of the prostatic urethra. The pseudocapsule cannot be separated from the gland itself. It has an anterior, posterior, and lateral surface. The prostate base is contiguous with the bladder superiorly. The apex of the prostate is contiguous with the striated urethral sphincter. Lateral to the prostate is the pubococcygeal portion of the levator ani and endopelvic fascia. Denonvilliers’ fascia, which separates the prostate from the rectum, is posterior to the prostate.

Vas Deferens and Seminal Vesicles

Arising from the tail of the epididymis, the vas deferens consists of a tortuous proximal portion and a dilated terminal portion called the ampulla. The ampulla is capable of storing sperm and lies posterior to the bladder. Bordering the base of the bladder, posteriorly, are the seminal vesicles. They also lie adjacent to the ampullae of the vasa deferentia and the distal ureters.

Vascular Anatomy

The prostatic artery is a branch of the internal iliac artery. It divides into capsular and urethral arteries. The capsular arteries supply two thirds of the gland; the urethral arteries supply the remaining third. Branches of the inferior vesical artery supply the seminal vesicles, and occasionally the base of the prostate gland. The neurovascular bundles located posterolaterally (at the confluence of the seminal vesicle and prostate bilaterally) provide the main neurovascular supply and drainage system of the prostate.

Zonal Anatomy

Traditionally, the prostate was divided into five major lobes (anterior, middle, posterior, and two lateral lobes) and two minor lobes (trigonal and subcervical lobes). McNeal derived a three-dimensional model of the prostate, as illustrated in Figure 121-3.

Figure 121-3 Anatomy of the prostate. A, Midsagittal plane. B, Coronal section (through the plane A-A′ in A). C, Oblique coronal section (through the plane B-B′ in A). D, Transverse section (through the plane C-C′ in A).

(A, Redrawn from McNeal JE: Normal and pathologic anatomy of prostate. Urology 17[Suppl 3]:11–16, 1981. B–D, Redrawn from Muldoon LD, Resnick MI: Normal anatomy of the prostate. In Resnick MI [ed]: Prostatic Ultrasonography. Philadelphia, BC Decker, 1990.)