Transrectal Ultrasound

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Transrectal Ultrasound AN

b TO DIAGNOSING PROSTATE CANCER

Johannah K. Stevens, RN; Jeffrey I. Miller, MD

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rostate cancer is the second most common cancer and is the third leading cause of cancer deaths among American men.' More than 96,000 cases are diagnosed annually and more than 27,000 deaths occur each year as a direct result of the disease.*As the population ages, both the prevalence of and the mortality associated with prostate cancer will increase. A high proportion of non-palpable prostatic tumors are potentially curable, thus the advent of transrectal ultrasonography has resulted in enthusiasm for detecting early prostate cancer. The cancer detection rate with this technique is approximately twice that achieved with a rectal examination alone.'

Johannah K. Stevens, RN, BS, is a staff nurse in the operating room at the Department of Veterans Affairs Medical Center, Tucson. She received her diploma in nursing f r o m the Albert Einstein Medical Center School of Nursing, Philadelphia, and her bachelor of science degree in health arts from the College 1166

Anatomy and Physiology

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he prostate is a glandular fibromuscular organ located just below the bladder, surrounding the male urethra (Fig 1). In the normal adult male, it weighs about 20 g and is roughly the size and shape of a chestnut. The prostate is separated from the rectum by a layer of connective tissue, and its posterior surface is easily palpable on digital rectal examination. It normally feels smooth, symmetric, and somewhat rubbery. Tubulo-alveolar glands in the prostate secrete a colorless fluid containing enzymes, citric acid, spermine, potassium, calcium, and

of St Francis, Joliet, Ill.

Jeffrey I. Miller, MD, is a senior resident in urology at the University of Arizona Health Sciences Center, Tucson. He received his medical degree at Johns Hopkins University, Baltimore.

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Fig 1. Midsagittal section of the prostate gland showing close relationship to rectum. (Reproduced with permission of Burroughs Welcome Co, North Carolina)

zinc into the prostatic ducts that empty into the urethra. The exact role of these secretions in reproduction is unclear. The prostate also is perforated by the ejaculatory ducts that carry sperm and seminal vesicle secretions into the proximal urethra: The growth and regulation of the prostate gland is controlled by testicular androgens. The prostate enlarges very slowly until puberty, when rapid growth occurs. This rapid growth continues until the middle of the third decade. After age 45, the prostatic glands and surrounding stroma may undergo hyperplasia or a benign proliferation known as benign prostatic hyperplasia (BPH). The glands most commonly involved are located in the periurethral or transitional region within the central aspect of the prostate. For this reason, BPH can cause early urethral compression resulting in voiding dysfunction. 1168

Most men over 50 will have pathologic evidence of benign prostatic hypertrophy. Although many men will develop voiding symptoms, only a minority of them will require pro~tatectomy.~ Prostate cancer, on the other hand, is an adenocarcinoma that arises in the peripheral regions of the gland. Because urethral compression and subsequent voiding symptoms are uncommon until late in the disease, about 40% of patients at the time of diagnosis will have advanced, incurable cancer.6 When prostate cancer is confined to the gland without any distant metastases or lymph node spread, it is potentially curable (Fig 2). Current treatment options include radiotherapy and radical prostatectomy. Once metastasis has occurred, treatment is only palliative. Hormonal manipulation can cause temporary remission in some patients.

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Fig 2. Typical early prostate cancer. (Reproduced with permission of Burroughs Welcome Co, North Carolina.)

Diagnosis

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any prostatic cancers are palpable on digital rectal examination. The tumor usually has a hard consistency and may produce a diffuse firmness or a discrete n ~ d u l eIf. ~x-ray studies, including bone scan, computerized tomography (CT) scan, and tumor marker levels such as prostatic specific antigen are within normal limits, the patient with a discrete nodule may be a candidate for curative treatment. Biopsy of the nodule or fm area is necessary to confirm the diagnosis of cancer. Some tumors are small or are located away from the posterior surface and cannot be palpated on rectal examination. Screening with transrectal ultrasound has aided in the diagnosis of nonpalpable tumors. Transurethral resection of the prostate for BPH will detect cancer in 10% to 28% of patients depending on their age.* Randomized controlled clinical trials to determine if nonpalpable tumors diagnosed by transrectal ultrasound will become biologically aggressive are necessary to decide if all men in the high-risk age group should undergo period-

ic routine screenings with transrectal ultrasound in addition to yearly rectal examinations. It is possible that treatment of these tumors might cause more morbidity than the disease i t ~ e l f . ~ Apart from its controversial role as a screening tool in asymptomatic men with normal rectal exams, transrectal ultrasonography is very useful in directing biopsies of clinically palpable tumors. Before the development of transrectal ultrasound, nodules commonly were biopsied either transrectally or transperineally using digital rectal examination to guide the biopsy needle toward the lesion. Although these techniques are still used, transrectal ultrasound-guided needle biopsy is rapidly becoming state of the art. This allows more accurate tumor localization and needle placement, and a smaller needle associated with fewer complications is used. Other uses of transrectal ultrasound include assessment of tumor extent and confinement to the prostate gland, estimation of prostate size, diagnosis of benign disease such as prostatic calculi and cysts, and evaluation of the seminal vesicles that lie above and posterior to the prostate. Transrectal ultrasound-guided needle biopsy 1169

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Fig 3. A 7 m H z transaxial probe (above). A 7 mHz longitudinal probe ( below).

of the prostate can be performed safely as an extension of the diagnostic procedure if a suspicious lesion is seen. The rectal mucosa is sensitive only to stretch; therefore, the ultrasound procedure is relatively painless, accurate, and rapid. There are various methods of biopsy depending on the type of ultrasound probe used. Basically, the target lesion is positioned along an electronic dotted biopsy line seen on the screen (ie, the puncture path). The biopsy needle is then introduced through the needle guide on the ultrasound probe. The tip of the needle can be seen on the monitor as a bright line as it traverses the rectal mucosa. When the needle tip is positioned just behind the lesion, the device is activated by pushing a button. The needle is seen advancing along the puncture path. A 17 mm tissue core is obtained. One of the most common techniques uses an automatic firing device with an 18-guage needle for prostatic biopsy. When activated, the inner needle advances 23 mm, exposing a 17 mm biopsy slot. A second firing of the device advances the outer cutting needle over the inner needle. This outer needle cuts the tissue core contained in the biopsy chamber. The spring loaded 1170

sequence of events is so rapid that it appears to be simultaneous."

Principles of Ultrasound

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ltrasound provides both new and complimentary information compared to the techniques of conventional x-ray, CT scan, nuclear medicine, and magnetic resonance imaging. Ultrasonic energy consists of mechanical vibrations of microscopic particles (ie, atoms and molecules) at inaudible frequencies above 20,000 cycles per second (ie, 20 kHz). Short pulses lasting less than one millionth of a second are launched into the patient several thousand times per second. The ultrasonic energy originates from a piezoelectric crystal on a transducer that is excited by a burst of electrical current. Energy pulses are received by nearby tissues and bounce back to the crystal. Some of the energy is transmitted through the tissue depending on the tissue's mechanical stiffness and mass density. The farther away the scanned tissue is from the crystal source, the longer it takes for the pulse to return. An image monitor using an

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Fig 4. Image control monitor with display screen and hard copy printout camera.

electronic beam scanner displays a series of bright spots in proportion to the returned echo’s strength. Structures within a scanned area can be differentiated by virtue of their different physical ability to transmit sound, a principle known as acoustic impedance.” Different tissues transmit sound at different speeds. The lower the frequency of the sound, the greater its ability to penetrate tissue, but the poorer the quality of the ultrasound picture. With transrectal ultrasound, the probe can be placed quite close to the prostate. Thus a frequency of about 7 mHz (ie, 7 million cycles per second) is usually ideal. This frequency is low enough to achieve adequate penetration of even the most anterior prostate tissue and also is high enough to provide good resolution. Because the transducer sends sound out along a line and receives it along this same line, the crystal needs to “sweep” across the entire organ for scanning to be complete. There are three methods of transducer sweep (ie. radial, sector, linear array). In the commonly used mechanical sector scanner, a transducer is rocked in an oscillating fashion by a motor creating a windshield wiper effect. The image on the screen appears pie shaped. Each sweep method has specific advantages and limitations. l2 1172

The basic transrectal ultrasound machine consists of a probe connected to an image control monitor. The probe is made of two parts: a freely movable inner assembly containing the transducer and a stationary outer assembly (Fig 3). A disposable rubber balloon or condom is attached over the outer unit. When inflated with water, it provides a coupling medium to facilitate imaging the prostate and to protect the rectal mucosa. l 3 A single plane probe allows visualization of the prostate in one plane only because of the fixed orientation of its transducer (eg, transaxial). For a complete examination of the prostate, a separate probe must be used to view the longitudinal plane. Biplanar probes use a single probe to view both planes by throwing a switch. These probes may contain one or two transducers. The image control monitor contains an image display screen (Fig 4). Different parameters such as level of sound amplification (ie, gain), image size, and orientation can be adjusted. Direct patient identification and labeling of different views can be entered on a keyboard and displayed on the screen. Cursors can be placed to mark and measure lesion size. Hard copies of images may be obtained for the per-

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Fig 5. Transrectal ultrasound of the prostate with the patient in left lateral decubitus position. manent record with an instant photography or multifocal camera.I4

Preoperative Preparation

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he typical patient scheduled for transrectal ultrasound is a middle-aged to elderly male with a palpably suspicious prostate on rectal examination. The urologist usually sees and examines the patient several weeks before the procedure. At this time, he or she writes a preoperative order sheet. Because bleeding can be a major complication of prostate biopsy, a preoperative bleeding profile (ie, prothrombin and partial thromboplastin time, platelet count) is necessary. Bleeding disorders should be diagnosed and if possible, corrected preoperatively. Patients should avoid aspirin products and nonsteroidal anti-inflammatory agents for seven to 10 days before the procedure, if a biopsy is planned. Other laboratory studies (eg, complete blood count, renal panel) are done at the physician's discretion. The physician should order a prostate specific antigen level (PSA) drawn from the patient at 1174

this time. Prostate specific antigen is a protein produced only by prostate epithelial cells. Diseases of the prostate, especially prostate cancer, produce elevations in the serum PSA. Prostate specific antigen can serve as a marker for prostatic cancer and serial levels can be followed after treatment to detect recurrence.lS Prostate biopsy can cause an extreme artificial elevation in serum PSA, therefore, it is important that PSA levels are drawn before biopsy. If drawn after prostate biopsy, the blood test should be repeated in two weeks for an accurate result. Although not proven to decrease the incidence of postbiopsy infection, mechanical rectal cleansing is probably wise. The physician can have the patient use either an enema or oral laxative. An empty rectum also facilitates examining the prostate. Preoperative antibiotics active against the usual bowel flora are used. Urine culture and sensitivity should be obtained and any urinary tract infection should be treated before the biopsy. Because most patients will not require intravenous access, the antibiotic can be given intramuscularly. Patients are encouraged to eat a light breakfast the morning of the procedure.

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Fig 6. Ultrasound of prostate gland shows focus of cancer as dark area between crossmarks.

Intraoperative Procedure

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ransrectal ultrasound is being done in many urologists’ offices, hospital urology clinics, or minor surgery operating rooms. In the latter case, the patient reports to the ambulatory surgery office one hour before the scheduled procedure. The perioperative nurse escorts the patient in a wheelchair to the examining room. He or she assists the patient into the left lateral decubitus position on the OR bed (Fig 5). The examination also can be performed in the lithotomy, supine, or sitting position. Sterile precautions are not used during this procedure, which is classified as contaminated. No skin preparation is necessary. The urologist instills 10 mL of 2% lidocaine jelly into the patient’s rectum and performs a digital rectal examination to confirm preoperative findings and to identify any rectal lesions such as hemorrhoids that would make placement of the probe technically difficult. He or she then inserts the probe 8 to 10 cm above the patient’s anal verge, and an image of the prostate is seen on the screen. The rubber condom or balloon covering the probe is then inflated with water

until it fits snugly against the rectal mucosa. The urologist obtains images of the entire gland in both axial and longitudinal planes. Prostate cancer usually appears hypoechoic or dark on the screen (Fig 6). The entire gland may appear asymmetric and the capsule may be deformed or irregular. The urologist visualizes the seminal vesicles lying above and behind the prostate to detect any evidence of tumor involvement. If clinical or sonographic evidence indicates the necessity, the urologist performs a biopsy of a suspicious area as described above (Fig 7). He or she places the tissue cores in formalin solution. During the procedure, the nurse monitors the patient’s vital signs and provides reassurance. If performed properly, there is minimal patient discomfort. The entire procedure takes about 20 minutes. l 6

Postoperative Course

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fter the probe is removed, the perioperative nurse transports the patient to the ambulatory care center where he remains for a minimum of 60 to 90 minutes. He is encouraged to take fluids. Discharge criteria 1175

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Fig 7. Biopsy gun is inserted next to the probe to perform prostate needle biopsy.

include stable vital signs and the patient’s ability to spontaneously void clear to cranberry colored urine without the presence of blood clots. No pain medication usually is necessary. Although serious complications after transrectal ultrasound-guided prostate needle biopsy are uncommon, the urologist warns the patient to report any signs or symptoms of urinary tract bleeding, rectal bleeding, infection, or urinary retention. Although not proven to decrease the incidence of postbiopsy infection and sepsis, the patient is given oral antibiotics for three to five days. One study reported on complications after 25 1 transrectal ultrasound-guided needle biopsies.” In this study, all patients received preoperative and postoperative oral antibiotics. TWO patients (0.8%) experienced fever or chills requiring hospitalization. Three patients (1.2%) had rectal bleeding from a mucosal tear requiring anoscopy and suturing. These three patients were taking aspirin or a nonsteroidal antiinflammatory agent. Only one patient developed urinary retention. No mention was made of clinically significant hematuria. The overall complication rate in this study was 2.4% with no major morbidity reported.

Quick return to normal activity is the norm for patients undergoing this procedure, and no activity restrictions are necessary. The patient is instructed to make a follow-up appointment with the urologist in one to two weeks to discuss the biopsy results and treatment course necessary. The ambulatory nursing staff makes a follow-up postoperative phone call the day following the procedure to check for complications.

Conclusion

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ifty to 75% of palpable prostate nodules are found to contain cancer on biopsy. The remainder contain benign hyperplasia, prostatic calculi, chronic prostatitis, or fibrosis.l* In view of the statistics, it is prudent for men (especially over age 50) to have a yearly digital rectal examination. If clinically indicated, a transrectal ultrasound with guided prostate needle biopsy appears to be the most accurate, safe, cost-effective, and expeditious means of detecting an underlying cancer. 0 Notes 1. W J Catalona, W W Scott, “Carcinoma of 1177

the prostate,” in Urology, fifth ed, P C Walsh et al, eds (Philadelphia: W B Saunders Co, 1986) 14761479. 2. Ibid. 3. G W Chodak, “Screening for prostate cancer: Role of ultrasonography,” The Urologic Clinics of North America 16 (November 1989) 657-661. 4. P C Walsh, “Diseases of the prostate,” in Cecil Textbook of Medicine, 17th ed, J B Wyngarded, L H Smith, Jr, eds (Philadelphia: W B Saunders Co, 1985) 1375; J F Redman, “Anatomy of the genitourinary gystem,” in Adult and Pediatric Urology, ed J Y Gillenwater et al (Chicago: Year Book Medical Publishers, Inc 1987) 37-41; E A Tanagho, “Anatomy of the genitourinary tract,” in General Urology, ed, D R Smith, 1lth ed (Los Altos, California: Lange Medical Publications, 1984); S L Robbins, S R Cotran, V Kumar, Pathologic Basis of Disease, third ed (Philadelphia: W B Saunders Co, 1984) 1099-1108. 5. Walsh, “Benign prostatic hyperplasia,” 12481265. 6. Catalona, Scott, “Carcinoma of the prostate,” 1476-1479. 7. Ibid. 8. Tanagho, “Anatomy of the genitourinary tract.” 9. Chodak, “Screening for prostate cancer: Role of ultrasonography,” 657-661. 10. S T Torp-Pedersen, F Lee, “Transrectal biopsy of the prostate guided by transrectal ultrasound,” The Urologic Clinics of North America 16 (November 1989) 703-712. 11. W A Riley, “Understanding ultrasound,” Contemporary Urology (October/November 1989) 49-58. 12. W H Cooner, “Physical principles of prostate ultrasonography,” in Monographs in Urology, vol 11 no 2, ed T A Stamey (Monteverde, Fla: Medical Directions Publishing Co, 1990) 18-32. 13. Cooner, “Physical principles of prostate ultrasonography,” 18-32. 14. Ibid; J P Smirnak, M I Resnick, “Prostatic ultrasonography,” in Urology Grand Rounds, no 18, ed E D Crawford (Chicago: McCann Healthcare Advertising, 1987) 2-9. 15. T A Stamey, “Prostate specific antigen in the diagnosis and treatment of adenocarcinoma of the prostate,’’in Monographs in Urology, vol 10 no 4, ed T A Stamey (Princeton, NJ: Medical Directions Publishing CO, 1989) 50-64. 16. Smirnak, Resnick, “Prostatic ultrasonography,” 2-9. 17. K K Hodge, J E McNeal, T A Stamey, “Ultrasound guided transrectal core biopsies of the palpably abnormal prostate,” Journal of Urology 142 (July 1989) 66-70. 1178

Admitting Patterns Surveyed Obstetricians and gynecologists admitted the most patients in 1989 anlong all specialities. Pulmonologists, however, generated the most revenue for hospitals, according to a survey reported in the Jan 20,199 1, issue of Hospitals. Obstetricians/gynecologists admitted an average of 155 patients during 1989. General practitioners/familyphysicians admitted 114 patients, and internists admitted 113. Pediatricians admitted an average of 109 patients and general surgeons an average of 84 patients, according to the article. The survey also suggests that physicians in larger hospitals admit fewer patients. Physicians practicing at hospitals with fewer than 50 beds admitted an average of 188 patients per year. Physicians at hospitals with more than 200 beds averaged 77 patients per year. Physicians at teaching hospitals admitted almost twice as many patients as those at nonteaching hospitals. Also, physicians in smaller communities admitted more patients in 1989. Admission rates were highest for physicians in the Southeast and Midwest sections of the United States and lowest in the West. Hospital inpatient revenue averaged $5 13,000 per physician in 1989, according to the survey. Pulmonologists were top revenue generators for hospitals bringing in $608,000 per year. Cardiovascular surgeons and internists were close behind with $604,000 and $603,000, respectively. The article stated that overall inpatient revenues for specialty physicians decreased 5% from the 1988 survey figures. Pediatricians and general family physicians reported 12% decreases in revenue in 1989 compared to 1988.