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Ultrasonographic evaluation of urethral stricture disease
ULTRASONOGRAPHIC EVALUATION OF URETHRAL STRICTURE DISEASE SAKTI DAS, M.D.
From the Department of Urology, Kaiser Permanente Medical Center, Walnut Creek, California ABSTRACT-Twenty-four male patients with known or suspected urethral stricture disease were evaluated using ultrasonic urethrography and standard retrograde x-ray urethrography for comparative analysis of the two techniques. Each patient also had cystoscopy for direct visual verification of the extent of the stricture. Ultrasonic urethrography proved a simple, yet sensitive and reliable, diagnostic study that can provide more accurate information regarding stricture length, lumen caliber, and extent of spongiofibrosis than radiologic urethrography. It allows examination of the urethra in different planes. The ultrasonic equipment is portable, and ultrasonic study provides the distinct advantage of avoiding ionizing radiation.
A comprehensive preoperative evaluation of urethral stricture is essential in determining the optimal therapy of this often indolent disease process. Apart from determining the cause, important parameters necessary in the therapeutic planning are the length, anatomic site, luminal caliber, and spongiofibrosis or lateral thickness of the strictured area. Radiologic retrograde urethrography and voiding cystourethrography has been the standard method of investigating the anatomy of urethral stricture. In 1988, McAninch, Laing, and Jeffrey’ reported their preliminary experience with sonourethrography in evaluating urethral strictures. At about the same time, we had been independently evaluating ultrasonography as an alternative imaging technique for urethrography. Our technique, although similar in principle, differs slightly in methodology from theirs. However, our results corroborate that ultrasonic urethrography provides more accurate reproduction of anatomic details as well as additional useful information regarding stricture disease compared with conventional radiologic urethrography. Material and Methods Twenty-four patients with known or suspected urethral stricture disease were evaluated
UROLOGY
/ SEPTEMBER1992
I VOLUME40,NUMBER3
using ultrasonic urethrography and retrograde radiologic urethrography. Both studies were done sequentially at the same visit. A 10F Foley catheter was inserted upward to a point just proximal to the fossa navicularis and its balloon inflated with 1 to 2 mL of water to secure the catheter in the urethra. Through this catheter, normal saline solution was injected by hand continually as the ultrasonic study progressed. Ultrasonic gel was applied to the ventral aspect of the penis, scrotum, and perineum. A 7.5 MHz linear transducer was applied over the corpus spongiosum on the ventral aspect. The saline-infused urethra was studied on the realtime screen as the probe was moved proximally. Suitable static photos of the areas of interest were obtained. In the areas of stricture, the probe was rotated 90” to obtain transverse cuts which provided additional information about the luminal caliber and spongiofibrosis. The length of the stricture and thickness of the spongiofibrosis were measured by caliper. Following ultrasonography, the patient was moved to the radiology suite and standard radiologic urethrography with oblique views was carried out by injecting radiographic contrast medium through the same catheter. The length and luminal diameter of the stricture were directly measured from the static films.
237
view FIGURE 1. (A) Ultrasonic urethrographic shows strictured area in proximal bulbar urethra; (B) retrograde x-ray WethTogTaphic film shows equivocal area of narrowing in bulbar urethra.
All patients had cystoscopic evaluation and subsequent treatment of urethral stricture. Results There were 27 distinct areas of stricture diagnosed in the 24 patients studied. All strictures were identified by both studies, excepting one in which radiologic urethrography was equivocal but ultrasonic urethrography was definitely pathognomonic of a stricture (Fig. 1). There were no false-positive results as confirmed by subsequent cystourethroscopy. Length of the stricture, luminal caliber, and extent of spongiofibrosis or thickness of the strictured wall were the parameters evaluated. Mean length was 0.6 cm longer in the ultrasonographic studies as compared with radiologic urethrography. The latter consistently underestimated the stricture lumen-narrowing and was unable to provide any information about the thickness of the strictured wall or The luminal caliber, comspongiofibrosis. pressibility, and extent of spongiofibrosis were demonstrated quite clearly with ultrasonic urethrography, especially in the cross-sectional views. Case Reports Case 1 A sixty-seven-year-old man, who had transurethral resection of the prostate three years
238
previously and a direct visual internal urethrotomy for a proximal bulbar urethral stricture two years later, complained of progressive slowing of the urinary stream with dysuria. Ultrasonic urethrography revealed a definite bulbar stricture (Fig. lA), but the radiologic urethrography was read by the radiologist as equivocal (Fig. 1B). Cystoscopy confirmed the findings of the ultrasonic study. The patient was treated with a repeat internal urethrotomy. Case 2 A seventeen-year-old boy with no history of trauma sought care during an episode of painless gross hematuria. Excretory urography revealed a normal upper urinary tract. On cystoscopy, a narrow bulbar urethral stricture was noted which did not allow the passage of the 19F cystoscope. Ultrasonic urethrography revealed a stricture 2 cm in length with dense spongiofibrosis (Fig. 2A and B). Subsequent retrograde urethrography showed a 1 cm bulbar stricture (Fig. 2C). The patient was successfully treated with open excision of the stricture and end-to-end urethroplasty. Case 3 A twenty-four-year-old man sought care for dysuria and a progressively slow urinary stream. Peak urine flow rate was 8 mllsec. In his childhood, he had sustained a bicycle injury
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FIGURE 2. (A) Ultrasonic urethrographic view shows bulbar urethral stricture 2 cm in length; (B) cross-sectional ultrasonic urethrographic views show dense spongiofibrosis and narrow lumen of stricture; (C) retrograde x-ray urethrographic film shows apparent involvement of stricture with shorter segment of urethra.
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Ultrasonic urethtographic view shows SttiCtUTe involving long segment of bulbar urethra with x-ray urethrographic film dense spongiofibrosis: (A) axial views; (B) cross-sectional view; (C)~‘e&gr&e depicts same stricture. FIGURE 3.
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with transient hematuria of one day in duration. Ultrasonic urethrography showed a long, bulbar urethral stricture with dense spongiofibrosis (Fig. 3A and B). Retrograde radiologic urethrography depicted a similar, shorter stricture (Fig. 3C). Cystoscopy confirmed the stricture, and the patient was treated by open incision of the stricture and substitution graft urethroplasty. Comment Ultrasonography for initial use in noninvasive evaluation of the upper urinary tract is expanding its role in the anatomic and functional study of the lower urinary tract as well. With the widespread advocacy of prostatic ultrasonography by urologists at large, the understanding and utility of this technology is now an integral part of our training and practice. Further application of ultrasonography in other areas of the genitourinary tract is only a natural extension of this learning process. In the early 198Os, reports of using abdominal ultrasonography to diagnose female urethral diverticula2 and using transperineal ultrasonography to evaluate the prostatic urethra of neonates with posterior urethral valves3 permeated the literature. The use of transrectal ultrasound in video monitoring of vesicourethral dysfunction was reported by Nishizawa and associates in 1982.4 Several subsequent reports reaffirmed the usefulness of ultrasonography in place of x-ray fluoroscopy in urodynamic evaluations,5xe whereas others have commented on some of its technical limitations.’ McAninch and associates’ pioneered the use of ultrasonography in studying the anterior urethra in patients with known urethral stricture. They scanned the fluid-filled urethra with a 5 MHz probe from the dorsal aspect of the penis to obviate near-field artifact. In contradistinction, we scanned the urethra from the ventral aspect using a 7.5 MHz probe. The clarity provided by a higher frequency probe eliminates any possible near-field defects of the relatively superficial anterior urethra. The normal urethra must not be compressed to produce a false-positive appearance of narrowing, and any area suggestive of stricture should be verified with cross-sectional imaging. Merkle and Wagner8 have reported a similar technique and instrumentation. Voluntary contraction of the external urethral sphincter during the study allows proper identification of the area of the sphincter and membranous urethra, which is
UROLOGY
I SEPTEMBER1992
I VOLUME40,NUMBER3
often equivocal in the radiologic urethrography films unless fluoroscopy is used. Despite the magnification factor in radiologic urethrography, the mean length of the stricture was shorter than with the ultrasonic studies, most probably because of such factors as obliquity of exposure and variable amount of stretch on the penis during the radiologic studies. Ultrasonography of the saline-filled urethra was more often able to depict subtle areas of irregularity in the urethral caliber and inelastic zones of spongiofibrosis. Radiologic urethrography more easily delineated finer periurethral tracts such as delicate false passages, sinuses, and Cowper’s ducts, that often elude ultrasonographic studies. The impact of these findings on the overall management of urethral strictures is minimal. Also, because of its more vertical orientation and deeper location, ultrasonographic evaluation of the posterior urethra is inadequate with the present technique. The thickness of the stricture or the extent of spongiofibrosis appears brighter sonographitally, with a stronger reflection zone, compared with the normal adjacent spongiosum. McAninch and associates’ found a strong correlation between this zone and the histologic extent of stricture in specimens obtained during open urethroplasty. We, however, have not been able to demarcate with certainty the junction where obvious spongiofibrosis merges with normal spongiosal area. The gradual fading of the pathologic process of inflammatory fibrosis precludes such demarcation. Ultrasonographic identification of spongiofibrosis, aside from its diagnostic significance, has been claimed to have definite therapeutic implications. Patients with spongiofibrosis of more extensive length and depth should benefit from open urethroplasty, whereas those with more limited segmental spongiofibrosis may respond to dilations or internal urethrotomy. Merkle and Wagner8 reported that recurrence after internal urethrotomy usually occurred in patients with more prominent scars. Ultrasonographic determination of the extent of scarring, therefore, allows patients to be selected for the proper treatment. Gluck and associates9 suggested intraoperative ultrasonography during internal urethrotomy to determine and control the length and depth of the incision under realtime monitoring. Ultrasonographic urethrography depicts the areas of more extensive spongiofibrosis, which often are not in the dorsal
241
aspect. The traditional U-o’clock-position urethrotomy in those circumstances may increase the chance of failure or recurrence. Real-time monitoring during ultrasonographic study prevents inadvertent overdistention of the urethra and extravasation, as is noted sometimes during radiologic urethrography. For the same reasons, patients find ultrasonographic study relatively more comfortable. Conclusion In conclusion, ultrasonographic urethrography is a sensitive and reliable diagnostic tool for comprehensive evaluation of anterior urethral stricture disease. Our comparative analysis found it to have the following distinct advantages over standard radiologic urethrography: (1) ultrasonography avoids ionizing radiation, especially to the gonads, which are often within the field of radiologic urethrography; (2) ultrasonic evaluation of postvoid residual urine in the bladder before urethrography indicates how the bladder empties against the outflow obstruction; (3) realtime ultrasonic studies allow prolonged periods of observation that can be printed as static images or videotaped for future reference; (4) ultrasonic study can better delineate intraurethral lesions, such as calculi, granulomas, neoplasms, and valves, that are often obscured in two-dimensional roentgenographic films of the contrast-filled urethra; (5) ultrasonic studies may reveal associated pathologic features in the neighboring structures, such as penile plaques, neoplasms, and vascular and prostatic pathologic processes; (6) cross-sectional views of the
242
urethral stricture, possible only with ultrasonography, can reveal the lumen size, compressibility, and thickness of the strictured urethra with more clarity; (7) information on presence and extent of spongiofibrosis, which helps determine the therapy most suitable for the particular patient, is evaluable only with ultrasonic urethrography; (8) ultrasonography can provide intraoperative monitoring to guide proper selection of internal urethrotomy site and depth; and (9) ultrasonic equipment is portable and can be transported to the bedside if necessary. Walnut Creek, California 94596 (DR. DAS) References 1. McAninch JW, Laing FC, and Jeffrey RB Jr: Sonourethrography in the evaluation of urethral strictures: a preliminary report, J Urol 139: 294 (1988). 2. Wexler JS, and McGovern TP: Ultrasonography of female urethral diverticula, AJR 134: 737 (1980). 3. Cremin B, and Aaronson IA: Ultrasonic diagnosis of posterior urethral valves in neonates, Br J Radio1 56: 435 (1983). 4. Nishizawa 0, et al: A new video urodynamics: combined ultrasonotomographic and urodynamic monitoring, Neurourol Urodynam 1: 295 (1982). 5. Shapeero LG, Friedland GW, and Perkash I: Transrectal sonographic voiding cystourethrography: studies in neuromuscular bladder dysfunction, AJR 141: 83 (1983). 6. Porena M, et al: Real-time transrectal sonographic voiding cystourethrography, Urology 30: 171 (1987). 7. Fellows Gl: Dvnamic ultrasonogranhv for voiding _ dvsfunc_ tion, Urol Clin horth Am 16: 809 (1989j. . 8. Merkle W, and Wagner W: Sonography of the distal male urethra: a new diagnostic procedure for urethral strictures: results of a retrospective study, J Urol 140: 1409 (1988). urethrogram: comparison to 9. Cluck CD, et al: Sonographic roentgenographic techniques in 22 patients, J Urol 140: 1404 (1988).
UROLOGY
/
SEPTEMBER
1992
/ VOLUME
40, NUMBER
3
From the Department of Urology, Kaiser Permanente Medical Center, Walnut Creek, California ABSTRACT-Twenty-four male patients with known or suspected urethral stricture disease were evaluated using ultrasonic urethrography and standard retrograde x-ray urethrography for comparative analysis of the two techniques. Each patient also had cystoscopy for direct visual verification of the extent of the stricture. Ultrasonic urethrography proved a simple, yet sensitive and reliable, diagnostic study that can provide more accurate information regarding stricture length, lumen caliber, and extent of spongiofibrosis than radiologic urethrography. It allows examination of the urethra in different planes. The ultrasonic equipment is portable, and ultrasonic study provides the distinct advantage of avoiding ionizing radiation.
A comprehensive preoperative evaluation of urethral stricture is essential in determining the optimal therapy of this often indolent disease process. Apart from determining the cause, important parameters necessary in the therapeutic planning are the length, anatomic site, luminal caliber, and spongiofibrosis or lateral thickness of the strictured area. Radiologic retrograde urethrography and voiding cystourethrography has been the standard method of investigating the anatomy of urethral stricture. In 1988, McAninch, Laing, and Jeffrey’ reported their preliminary experience with sonourethrography in evaluating urethral strictures. At about the same time, we had been independently evaluating ultrasonography as an alternative imaging technique for urethrography. Our technique, although similar in principle, differs slightly in methodology from theirs. However, our results corroborate that ultrasonic urethrography provides more accurate reproduction of anatomic details as well as additional useful information regarding stricture disease compared with conventional radiologic urethrography. Material and Methods Twenty-four patients with known or suspected urethral stricture disease were evaluated
UROLOGY
/ SEPTEMBER1992
I VOLUME40,NUMBER3
using ultrasonic urethrography and retrograde radiologic urethrography. Both studies were done sequentially at the same visit. A 10F Foley catheter was inserted upward to a point just proximal to the fossa navicularis and its balloon inflated with 1 to 2 mL of water to secure the catheter in the urethra. Through this catheter, normal saline solution was injected by hand continually as the ultrasonic study progressed. Ultrasonic gel was applied to the ventral aspect of the penis, scrotum, and perineum. A 7.5 MHz linear transducer was applied over the corpus spongiosum on the ventral aspect. The saline-infused urethra was studied on the realtime screen as the probe was moved proximally. Suitable static photos of the areas of interest were obtained. In the areas of stricture, the probe was rotated 90” to obtain transverse cuts which provided additional information about the luminal caliber and spongiofibrosis. The length of the stricture and thickness of the spongiofibrosis were measured by caliper. Following ultrasonography, the patient was moved to the radiology suite and standard radiologic urethrography with oblique views was carried out by injecting radiographic contrast medium through the same catheter. The length and luminal diameter of the stricture were directly measured from the static films.
237
view FIGURE 1. (A) Ultrasonic urethrographic shows strictured area in proximal bulbar urethra; (B) retrograde x-ray WethTogTaphic film shows equivocal area of narrowing in bulbar urethra.
All patients had cystoscopic evaluation and subsequent treatment of urethral stricture. Results There were 27 distinct areas of stricture diagnosed in the 24 patients studied. All strictures were identified by both studies, excepting one in which radiologic urethrography was equivocal but ultrasonic urethrography was definitely pathognomonic of a stricture (Fig. 1). There were no false-positive results as confirmed by subsequent cystourethroscopy. Length of the stricture, luminal caliber, and extent of spongiofibrosis or thickness of the strictured wall were the parameters evaluated. Mean length was 0.6 cm longer in the ultrasonographic studies as compared with radiologic urethrography. The latter consistently underestimated the stricture lumen-narrowing and was unable to provide any information about the thickness of the strictured wall or The luminal caliber, comspongiofibrosis. pressibility, and extent of spongiofibrosis were demonstrated quite clearly with ultrasonic urethrography, especially in the cross-sectional views. Case Reports Case 1 A sixty-seven-year-old man, who had transurethral resection of the prostate three years
238
previously and a direct visual internal urethrotomy for a proximal bulbar urethral stricture two years later, complained of progressive slowing of the urinary stream with dysuria. Ultrasonic urethrography revealed a definite bulbar stricture (Fig. lA), but the radiologic urethrography was read by the radiologist as equivocal (Fig. 1B). Cystoscopy confirmed the findings of the ultrasonic study. The patient was treated with a repeat internal urethrotomy. Case 2 A seventeen-year-old boy with no history of trauma sought care during an episode of painless gross hematuria. Excretory urography revealed a normal upper urinary tract. On cystoscopy, a narrow bulbar urethral stricture was noted which did not allow the passage of the 19F cystoscope. Ultrasonic urethrography revealed a stricture 2 cm in length with dense spongiofibrosis (Fig. 2A and B). Subsequent retrograde urethrography showed a 1 cm bulbar stricture (Fig. 2C). The patient was successfully treated with open excision of the stricture and end-to-end urethroplasty. Case 3 A twenty-four-year-old man sought care for dysuria and a progressively slow urinary stream. Peak urine flow rate was 8 mllsec. In his childhood, he had sustained a bicycle injury
UROLOGY
I SEPTEMBER1992 / VOLUME40,NUMBER3
FIGURE 2. (A) Ultrasonic urethrographic view shows bulbar urethral stricture 2 cm in length; (B) cross-sectional ultrasonic urethrographic views show dense spongiofibrosis and narrow lumen of stricture; (C) retrograde x-ray urethrographic film shows apparent involvement of stricture with shorter segment of urethra.
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i VOLUME40,NUMBER3
239
Ultrasonic urethtographic view shows SttiCtUTe involving long segment of bulbar urethra with x-ray urethrographic film dense spongiofibrosis: (A) axial views; (B) cross-sectional view; (C)~‘e&gr&e depicts same stricture. FIGURE 3.
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with transient hematuria of one day in duration. Ultrasonic urethrography showed a long, bulbar urethral stricture with dense spongiofibrosis (Fig. 3A and B). Retrograde radiologic urethrography depicted a similar, shorter stricture (Fig. 3C). Cystoscopy confirmed the stricture, and the patient was treated by open incision of the stricture and substitution graft urethroplasty. Comment Ultrasonography for initial use in noninvasive evaluation of the upper urinary tract is expanding its role in the anatomic and functional study of the lower urinary tract as well. With the widespread advocacy of prostatic ultrasonography by urologists at large, the understanding and utility of this technology is now an integral part of our training and practice. Further application of ultrasonography in other areas of the genitourinary tract is only a natural extension of this learning process. In the early 198Os, reports of using abdominal ultrasonography to diagnose female urethral diverticula2 and using transperineal ultrasonography to evaluate the prostatic urethra of neonates with posterior urethral valves3 permeated the literature. The use of transrectal ultrasound in video monitoring of vesicourethral dysfunction was reported by Nishizawa and associates in 1982.4 Several subsequent reports reaffirmed the usefulness of ultrasonography in place of x-ray fluoroscopy in urodynamic evaluations,5xe whereas others have commented on some of its technical limitations.’ McAninch and associates’ pioneered the use of ultrasonography in studying the anterior urethra in patients with known urethral stricture. They scanned the fluid-filled urethra with a 5 MHz probe from the dorsal aspect of the penis to obviate near-field artifact. In contradistinction, we scanned the urethra from the ventral aspect using a 7.5 MHz probe. The clarity provided by a higher frequency probe eliminates any possible near-field defects of the relatively superficial anterior urethra. The normal urethra must not be compressed to produce a false-positive appearance of narrowing, and any area suggestive of stricture should be verified with cross-sectional imaging. Merkle and Wagner8 have reported a similar technique and instrumentation. Voluntary contraction of the external urethral sphincter during the study allows proper identification of the area of the sphincter and membranous urethra, which is
UROLOGY
I SEPTEMBER1992
I VOLUME40,NUMBER3
often equivocal in the radiologic urethrography films unless fluoroscopy is used. Despite the magnification factor in radiologic urethrography, the mean length of the stricture was shorter than with the ultrasonic studies, most probably because of such factors as obliquity of exposure and variable amount of stretch on the penis during the radiologic studies. Ultrasonography of the saline-filled urethra was more often able to depict subtle areas of irregularity in the urethral caliber and inelastic zones of spongiofibrosis. Radiologic urethrography more easily delineated finer periurethral tracts such as delicate false passages, sinuses, and Cowper’s ducts, that often elude ultrasonographic studies. The impact of these findings on the overall management of urethral strictures is minimal. Also, because of its more vertical orientation and deeper location, ultrasonographic evaluation of the posterior urethra is inadequate with the present technique. The thickness of the stricture or the extent of spongiofibrosis appears brighter sonographitally, with a stronger reflection zone, compared with the normal adjacent spongiosum. McAninch and associates’ found a strong correlation between this zone and the histologic extent of stricture in specimens obtained during open urethroplasty. We, however, have not been able to demarcate with certainty the junction where obvious spongiofibrosis merges with normal spongiosal area. The gradual fading of the pathologic process of inflammatory fibrosis precludes such demarcation. Ultrasonographic identification of spongiofibrosis, aside from its diagnostic significance, has been claimed to have definite therapeutic implications. Patients with spongiofibrosis of more extensive length and depth should benefit from open urethroplasty, whereas those with more limited segmental spongiofibrosis may respond to dilations or internal urethrotomy. Merkle and Wagner8 reported that recurrence after internal urethrotomy usually occurred in patients with more prominent scars. Ultrasonographic determination of the extent of scarring, therefore, allows patients to be selected for the proper treatment. Gluck and associates9 suggested intraoperative ultrasonography during internal urethrotomy to determine and control the length and depth of the incision under realtime monitoring. Ultrasonographic urethrography depicts the areas of more extensive spongiofibrosis, which often are not in the dorsal
241
aspect. The traditional U-o’clock-position urethrotomy in those circumstances may increase the chance of failure or recurrence. Real-time monitoring during ultrasonographic study prevents inadvertent overdistention of the urethra and extravasation, as is noted sometimes during radiologic urethrography. For the same reasons, patients find ultrasonographic study relatively more comfortable. Conclusion In conclusion, ultrasonographic urethrography is a sensitive and reliable diagnostic tool for comprehensive evaluation of anterior urethral stricture disease. Our comparative analysis found it to have the following distinct advantages over standard radiologic urethrography: (1) ultrasonography avoids ionizing radiation, especially to the gonads, which are often within the field of radiologic urethrography; (2) ultrasonic evaluation of postvoid residual urine in the bladder before urethrography indicates how the bladder empties against the outflow obstruction; (3) realtime ultrasonic studies allow prolonged periods of observation that can be printed as static images or videotaped for future reference; (4) ultrasonic study can better delineate intraurethral lesions, such as calculi, granulomas, neoplasms, and valves, that are often obscured in two-dimensional roentgenographic films of the contrast-filled urethra; (5) ultrasonic studies may reveal associated pathologic features in the neighboring structures, such as penile plaques, neoplasms, and vascular and prostatic pathologic processes; (6) cross-sectional views of the
242
urethral stricture, possible only with ultrasonography, can reveal the lumen size, compressibility, and thickness of the strictured urethra with more clarity; (7) information on presence and extent of spongiofibrosis, which helps determine the therapy most suitable for the particular patient, is evaluable only with ultrasonic urethrography; (8) ultrasonography can provide intraoperative monitoring to guide proper selection of internal urethrotomy site and depth; and (9) ultrasonic equipment is portable and can be transported to the bedside if necessary. Walnut Creek, California 94596 (DR. DAS) References 1. McAninch JW, Laing FC, and Jeffrey RB Jr: Sonourethrography in the evaluation of urethral strictures: a preliminary report, J Urol 139: 294 (1988). 2. Wexler JS, and McGovern TP: Ultrasonography of female urethral diverticula, AJR 134: 737 (1980). 3. Cremin B, and Aaronson IA: Ultrasonic diagnosis of posterior urethral valves in neonates, Br J Radio1 56: 435 (1983). 4. Nishizawa 0, et al: A new video urodynamics: combined ultrasonotomographic and urodynamic monitoring, Neurourol Urodynam 1: 295 (1982). 5. Shapeero LG, Friedland GW, and Perkash I: Transrectal sonographic voiding cystourethrography: studies in neuromuscular bladder dysfunction, AJR 141: 83 (1983). 6. Porena M, et al: Real-time transrectal sonographic voiding cystourethrography, Urology 30: 171 (1987). 7. Fellows Gl: Dvnamic ultrasonogranhv for voiding _ dvsfunc_ tion, Urol Clin horth Am 16: 809 (1989j. . 8. Merkle W, and Wagner W: Sonography of the distal male urethra: a new diagnostic procedure for urethral strictures: results of a retrospective study, J Urol 140: 1409 (1988). urethrogram: comparison to 9. Cluck CD, et al: Sonographic roentgenographic techniques in 22 patients, J Urol 140: 1404 (1988).
UROLOGY
/
SEPTEMBER
1992
/ VOLUME
40, NUMBER
3