DOI: 10.1148/rg.24si045504
RadioGraphics 2004;24:S195-S216
© RSNA, 2004
LOWER GENITOURINARY TRACT IMAGING |
Imaging of Urethral Disease: A Pictorial Review1
Akira Kawashima, MD,
Carl M. Sandler, MD2,
Neil F. Wasserman, MD,
Andrew J. LeRoy, MD,
Bernard F. King, Jr, MD and
Stanford M. Goldman, MD
1 From the Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 (A.K., A.J.L., B.F.K.); the Department of Radiology, University of Texas-Houston Medical School, Houston, Tex (C.M.S., S.M.G.); and the Department of Radiology, Veterans Affairs Medical Center, University of Minnesota, Minneapolis (N.F.W.). Presented as an education exhibit at the 2003 RSNA scientific assembly. Received February 4, 2004; revision requested March 9 and received May 5; accepted May 11. All authors have no financial relationships to disclose. Address correspondence to A.K. (e-mail: kawashima.akira@mayo.edu).
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Abstract
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Retrograde urethrography and voiding cystourethrography are the modalities of choice for imaging the urethra. Cross-sectional imaging modalities, including ultrasonography, magnetic resonance (MR) imaging, and computed tomography, are useful for evaluating periurethral structures. Retrograde urethrography is the primary imaging modality for evaluating traumatic injuries and inflammatory and stricture diseases of the male urethra. Sonourethrography plays an important role in the assessment of the thickness and length of bulbar urethral stricture. Although voiding cystourethrography is frequently used to evaluate urethral diverticula in women, MR imaging is highly sensitive in the demonstration of these entities. MR imaging is also accurate in the local staging of urethral tumors.
© RSNA, 2004
Index Terms: Urethra • Urethra, abnormalities, 84.20, 84.23, 84.245, 84.41, 84.45. 85.20, 85.23, 85.245, 85.41, 85.45 • Urethra, MR, 84.1214, 85.1214 • Urethra, neoplasms, 84.32, 84.33, 85.32, 85.33 • Urethra, radiography, 84.1234, 85.1235 • Urethra, stenosis or obstruction, 84.1452, 85.1452 • Urethra, US, 84.1298, 85.1298
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LEARNING OBJECTIVES FOR TEST 5
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After reading this article and taking the test, the reader will be able to:
- Describe the anatomy of the urethra as well as the technique and pitfalls of urethrography.
- Discuss diseases of the urethra in adults.
- Identify the key features of urethral disease at urethrography and cross-sectional imaging.
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Introduction
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In this article, we review the anatomy and diseases of the urethra in adults. Although we focus on conventional urethrography, we discuss and illustrate the key imaging features of urethral diseases at both urethrography and cross-sectional imaging. The article is organized as follows: (a) normal anatomy of the urethra, (b) urethrographic techniques, (c) traumatic injuries, (d) acquired inflammatory diseases, (e) urethral strictures, (f) acquired female urethral diverticula, (g) urethral calculi, and (h) primary and metastatic tumors. Because the focus of this article is on the adult urethra, we do not discuss congenital anomalies.
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Normal Anatomy of the Urethra
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Male Urethra
The male urethra varies from 17.5 to 20 cm in length and consists of anterior and posterior portions, each of which is subdivided into two parts. The anterior urethra extends from the external meatus to the inferior edge of the urogenital diaphragm, coursing through the corpus spongiosum. The anterior urethra is conventionally divided into the penile (or pendulous) and bulbous parts at the penoscrotal junction on the basis of clinical and imaging findings. The pendulous portion terminates in the glans penis to form the fossa navicularis, which is 1–1.5 cm long. The proximal portion of the bulbous urethra is dilated and termed the "sump" of the bulbous urethra; just proximal to the sump, the bulbous urethra assumes a conical shape at the bulbomembranous junction. This portion of the bulb is known as the "cone." The anterior urethra has periurethral Littré glands, which are more numerous at the dorsal aspect of the penile urethra and in the bulbous urethral sump. The Cowper glands are two pea-sized glands that lie within the urogenital diaphragm on each side of the membranous portion of the posterior urethra. The ducts of the Cowper glands are 2 cm long and empty into the bulbous urethral sump on either side of midline.
The posterior urethra is divided into the prostatic and membranous urethras. The prostatic urethra is approximately 3.5 cm long and passes through the prostate slightly anterior to midline. A longitudinal ridge of smooth muscle (urethral crest) extends from the bladder neck to the membranous urethra on the posterior wall of the posterior urethra. This longitudinal ridge continues into the verumontanum, a 1-cm-long ovoid mound that lies in the posterior wall of the prostatic urethra. In the center of the verumontanum lies the prostatic utricle, a small saccular depression that is a vestigial remnant of the müllerian duct. Just distal and lateral to the utricle are the orifices of the paired ejaculatory ducts. The prostatic glands empty directly into the prostatic urethra via multiple small openings that surround the verumontanum. The prostatic urethra then tapers distally into the membranous urethra, which is approximately 1–1.5 cm long and ends at the inferior aspect of the urogenital diaphragm.
The proximal (internal) urethral sphincter extends from the bladder neck through the prostatic urethra above the verumontanum. Although it is similar to the detrusor muscle, it has different neurogenic innervation. The distal (external) sphincter has both intrinsic and extrinsic components. The "intrinsic" urethral sphincter is a concentric muscular structure and lies in the distal third of the prostatic urethra below the mound of the verumontanum and surrounds the membranous urethra. Both the internal and intrinsic sphincters are composed of smooth muscle and function as muscles that maintain passive continence. The internal sphincter functions as the primary continence sphincter and the intrinsic sphincter as the secondary continence sphincter. The extrinsic sphincter is a paraurethral, striated, voluntary muscle with contributions from the levator ani complex. The sphincter surrounds the membranous urethra and is involved in active continence.
Female Urethra
The female urethra is 4 cm long and extends from the bladder neck at the urethrovesical junction to the vestibule, where it forms the external meatus between the labia minora. Many small periurethral glands open into the urethra. Distally, these glands group together on either side of the urethra (Skene glands) and empty through two small ducts to either side of the external meatus. The proximal part of the urethral wall is made up of two layers of smooth muscle that are contiguous with the smooth muscle of the bladder neck. The inner layer of the smooth muscle is longitudinal, and the thinner outer layer is circular. The outer portion of the urethra is composed of striated muscle, which, in the upper two-thirds of the urethra, is primarily circular and extends proximally to blend with the bladder base. The lower portion of the urethra is intimately situated next to the anterior vaginal wall and enveloped by common musculature (the urethrovaginal sphincter), which extends to the inferior pubic ramus above the urogenital diaphragm.
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Urethrographic Techniques
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Retrograde Urethrography
Retrograde urethrography is considered to be the best initial study for urethral and periurethral imaging in men and is indicated in the evaluation of urethral injuries, strictures, and fistulas (1,2). Retrograde urethrography is a straightforward, readily available, cost-effective examination. The external meatus is prepared in a standard sterile fashion for the placement of a conventional 16- or 18-F Foley catheter. The catheter, with both the irrigating syringe and inflating (saline solution) syringe attached, should be flushed before use. When the balloon portion of the catheter is seated in the fossa navicularis of the penile urethra, the balloon is inflated with 1.0–1.5 mL of saline solution while the port is held with the free hand to partially inflate the balloon (2). Lubrication is not recommended because it may prevent the balloon from remaining in place for optimal occlusion. The patient is placed in a supine 45° oblique position. The penis should be placed laterally over the proximal thigh with moderate traction. The patient should be reassured about the discomfort that is experienced during balloon inflation. Then, 20–30 mL of 60% iodinated contrast material is injected under fluoroscopic guidance so that the anterior urethra is filled. Commonly, spasm of the external urethral sphincter will be encountered, which prevents filling of the deep bulbar, membranous, and prostatic urethras. Slow, gentle pressure is usually needed to overcome this resistance. Spot radiographs are obtained when there is visual confirmation of contrast material flowing into the bladder.
If properly administered, contrast material can be seen to jet through the bladder neck into the bladder. The verumontanum is seen as an ovoid filling defect in the posterior part of the prostatic urethra. The distal end of the verumontanum marks the proximal boundary of the membranous urethra, which is approximately 1 cm long and is that portion of the urethra that passes through the urogenital diaphragm. This is also the region of the external sphincter of the urethra. The distal boundary of the membranous urethra (the bulbomembranous junction) is the cone of the bulbar urethra. The identification of the bulbomembranous junction on a retrograde urethrogram is very important for assessing patients with urethral disease as well as for planning urologic procedures. When the posterior urethra is optimally opacified and the verumontanum visible, the bulbomembranous junction can be identified 1–1.5 cm distal to the inferior margin of the verumontanum. When the posterior urethra is suboptimally opacified, the bulbomembranous junction can be arbitrarily localized where an imaginary line connecting the inferior margins of the obturator foramina intersects the urethra.
The anterior urethra extends from its origin at the end of the membranous urethra to the urethral meatus. It is divided into the bulbar (most proximal) segment and the penile (pendulous) segment. There is usually mild angulation of the urethra where these two segments join at the penoscrotal junction. Contraction or spasm of the constrictor nudae muscle, a deep musculotendinous sling of the bulbocavernous muscle, may cause anterior or, less frequently, circumferential indentation of the proximal bulbous urethra at retrograde urethrography (3). This bulbous urethral indentation should not be confused with urethral stricture (Fig 1). If the membranous urethra can be identified, it will not be confused with a stricture. Narrowing elsewhere in the urethra will be clearly defined as separate from the membranous urethra and, therefore, representative of a pathologic stricture. If the patient is not positioned sufficiently oblique, the bulbous urethra will appear foreshortened and will therefore not be adequately evaluated (Fig 2). Filling of the Cowper ducts should not be misinterpreted as extravasation (Fig 3). Opacification of the prostatic ducts, Cowper ducts, and periurethral Littré glands is often, but not necessarily, associated with urethral inflammatory and stricture disease. If the integrity of the urethral mucosal lining is disrupted by increased pressure during contrast material injection, intravasation of contrast material with opacification of the corpora and draining veins may occur.
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Figure 1. Retrograde urethrogram shows a focal smooth indentation (arrow) on the anterior aspect of the proximal bulbous urethra by the compressor nudae muscle. (Reprinted, with permission, from reference 3.)
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Figure 2a. Affect of patient positioning on the appearance of the urethra during retrograde urethrography. (a) Retrograde urethrogram obtained with the patient supine shows the bulbous urethra as a diverticulum-like outpouching. (b) On a retrograde urethrogram obtained after the patient was placed in a steep oblique position with the penis stretched, the penoscrotal junction and bulbous urethra have a normal appearance.
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Figure 2b. Affect of patient positioning on the appearance of the urethra during retrograde urethrography. (a) Retrograde urethrogram obtained with the patient supine shows the bulbous urethra as a diverticulum-like outpouching. (b) On a retrograde urethrogram obtained after the patient was placed in a steep oblique position with the penis stretched, the penoscrotal junction and bulbous urethra have a normal appearance.
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Voiding Cystourethrography
Voiding cystourethrography is currently the most commonly used imaging method in the evaluation of the female urethra and male posterior urethra. Voiding urethrography is usually performed after the bladder is filled with contrast material via a transurethral or suprapubic catheter. After the transurethral catheter is withdrawn, the patient voids under fluoroscopic observation and spot radiographs of the bladder and urethra are obtained. During active voiding, the bladder neck opens widely and becomes funnel shaped in both male and female patients by means of the internal sphincter mechanism. In male patients, the verumontanum appears elongated and the proximal bulbar urethra has a less conical appearance. However, the membranous urethra remains the narrowest segment between these parts of the urethra, even though it may dilate up to 6 or 7 mm in diameter during voiding. Voiding cystourethrography may not demonstrate certain abnormalities of the male anterior urethra because the normal anterior urethra is not fully distended to the degree seen at retrograde urethrography.
A retrograde study is the most appropriate way to evaluate the anterior part of the urethra, and a voiding study is the most appropriate way to evaluate the posterior part of the urethra; therefore, "dynamic" urethrography represents a synergy of these two imaging techniques.
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Traumatic Injuries
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Blunt Urethral Trauma
Blunt urethral trauma traditionally has been classified anatomically as either anterior or posterior injury. Posterior urethral injury usually is caused by a crushing force to the pelvis (eg, from a high-speed automobile accident) and is associated with pelvic fractures. Posterior urethral injury has been reported to occur in 4%–14% of patients with pelvic fracture (4). In pelvic fracture, up to 20% of male patients with urethral injury also have associated bladder laceration. Conversely, anterior urethral injury usually results from a straddle pelvic injury and is most often isolated. When there is blood at the meatus, which is present in about one-half of significant urethral injuries, retrograde urethrography should be performed immediately to assess for urethral injury. Blind urethral catheterization is contraindicated in patients suspected of having urethral injury because the catheter could be misplaced into a pelvic hematoma through a urethral injury site. When urethral injury is demonstrated, a suprapubic catheter should be placed for immediate endoscopically assisted stent placement or delayed reconstruction procedures.
In 1977, Colapinto and McCallum (4) classified posterior urethral injuries into three types on the basis of findings at retrograde urethrography. In type I injury, there is rupture of the puboprostatic ligaments. Although the prostatic urethra is stretched, the continuity of the urethra is maintained (Fig 4). In type II injury, the membranous urethra is torn above an intact urogenital diaphragm, which prevents contrast material extravasation from extending into the perineum (Fig 5). Type II injuries have been reported to occur in 15% of cases (4). In type III injury, the most common form of urethral injury, the membranous urethra is ruptured but the injury extends into the proximal bulbous urethra because of laceration of the urogenital diaphragm (Fig 6). Type III urethral injury is characterized at urethrography by contrast material extravasation not only into the pelvic extraperitoneal space but also into the perineum. Complete disruption of the male membranous urethra, which occurs in both type II and III urethral injury, may result in dislocation of the bladder out of the pelvis, which appears as "pie in the sky" at excretory urography. Although the Colapinto and McCallum classification scheme is described as classifying posterior urethral injuries, type III injury actually extends into the bulbous portion of the anterior urethra. Type II and III injuries may be associated with incontinence related to traumatic damage to the external sphincter. Ali et al (5) recently reported computed tomographic (CT) findings in urethral injuries. In type III urethral injury, CT demonstrates urinary contrast material extravasation at and below the urogenital diaphragm.
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Figure 4a. Intact but stretched posterior urethra following blunt trauma (type I urethral injury). (a) Retrograde urethrogram reveals stretching of the posterior urethra. Diastasis of the pubic symphysis was diagnosed. (b) Drawing illustrates type I urethral injury.
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Figure 4b. Intact but stretched posterior urethra following blunt trauma (type I urethral injury). (a) Retrograde urethrogram reveals stretching of the posterior urethra. Diastasis of the pubic symphysis was diagnosed. (b) Drawing illustrates type I urethral injury.
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Figure 5a. Posterior urethral rupture above the intact urogenital diaphragm following blunt trauma (type II urethral injury). (a) Partial type II urethral injury. Retrograde urethrogram demonstrates contrast material extravasation confined to the area above the normal cone-shaped proximal portion of the bulbous urethra. However, contrast material flows through the prostatic urethral lumen into the bladder. Fracture of the left pubic ramus was diagnosed. (b) Complete type II urethral injury. Retrograde urethrogram shows a large amount of contrast material extravasation without flow into the prostatic urethra or bladder. Fracture of the right pubic ramus was diagnosed. (c) Drawing illustrates type II urethral injury.
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Figure 5b. Posterior urethral rupture above the intact urogenital diaphragm following blunt trauma (type II urethral injury). (a) Partial type II urethral injury. Retrograde urethrogram demonstrates contrast material extravasation confined to the area above the normal cone-shaped proximal portion of the bulbous urethra. However, contrast material flows through the prostatic urethral lumen into the bladder. Fracture of the left pubic ramus was diagnosed. (b) Complete type II urethral injury. Retrograde urethrogram shows a large amount of contrast material extravasation without flow into the prostatic urethra or bladder. Fracture of the right pubic ramus was diagnosed. (c) Drawing illustrates type II urethral injury.
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Figure 5c. Posterior urethral rupture above the intact urogenital diaphragm following blunt trauma (type II urethral injury). (a) Partial type II urethral injury. Retrograde urethrogram demonstrates contrast material extravasation confined to the area above the normal cone-shaped proximal portion of the bulbous urethra. However, contrast material flows through the prostatic urethral lumen into the bladder. Fracture of the left pubic ramus was diagnosed. (b) Complete type II urethral injury. Retrograde urethrogram shows a large amount of contrast material extravasation without flow into the prostatic urethra or bladder. Fracture of the right pubic ramus was diagnosed. (c) Drawing illustrates type II urethral injury.
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Figure 6a. Posterior urethral rupture extending through the urogenital diaphragm to involve the bulbous urethra following blunt trauma (type III urethral injury). (a) Retrograde urethrogram reveals contrast material extravasation at the membranous urethra (arrow). The contrast material extends below the urogenital diaphragm and surrounds the proximal bulbous urethra. (b) Drawing illustrates type III urethral injury.
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Figure 6b. Posterior urethral rupture extending through the urogenital diaphragm to involve the bulbous urethra following blunt trauma (type III urethral injury). (a) Retrograde urethrogram reveals contrast material extravasation at the membranous urethra (arrow). The contrast material extends below the urogenital diaphragm and surrounds the proximal bulbous urethra. (b) Drawing illustrates type III urethral injury.
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In 1997, Goldman et al (6) proposed a new unified classification system for urethral injuries following blunt trauma based on the anatomic location of the injury. The new classification system modifies and extends the Colapinto and McCallum system (type I–III injuries) into five types, with the addition of bladder base injuries (type IV and IVa injuries) (Fig 7) and straddle anterior urethral injury (type V injury). Bladder base injuries were believed to be of particular concern because the bladder neck is the site of the internal sphincter, which is the primary continence sphincter. Goldman et al suggested that patients with these injuries be considered for surgical therapy because there is the potential for incontinence if injury of the internal urethral sphincter is not appreciated. In addition, a second type of injury (type IVa injury), extraperitoneal bladder rupture at the base of the bladder that does not extend into the bladder neck, was included because it was believed that the extravasation from a laceration in this location would simulate a true type IV urethral injury (Fig 8). Because type IVa injuries do not extend into the bladder neck, there is less concern for incontinence as a result of damage to the internal sphincter; these injuries may be managed nonsurgically with bladder catheter drainage only. On the basis of the radiographic findings, extension of injury into the bladder neck and proximal urethra cannot be excluded, and type IVa urethral injuries are radiologically indistinguishable from true type IV injuries.
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Figure 7a. Type IV urethral injury from blunt trauma. (a) Retrograde urethrogram reveals extraperitoneal periurethral contrast material extravasation at the bladder neck (arrow). The bladder is pear shaped, indicative of perivesical hematoma. Diastasis of the pubic symphysis was diagnosed. (b) Drawing illustrates type IV urethral injury.
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Figure 7b. Type IV urethral injury from blunt trauma. (a) Retrograde urethrogram reveals extraperitoneal periurethral contrast material extravasation at the bladder neck (arrow). The bladder is pear shaped, indicative of perivesical hematoma. Diastasis of the pubic symphysis was diagnosed. (b) Drawing illustrates type IV urethral injury.
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Figure 8a. (a) Retrograde urethrogram obtained in a 32-year-old man with bladder base injury following blunt trauma (type IVa urethral injury) shows extraperitoneal contrast material extravasation that extends from the elevated bladder base and surrounds the proximal urethra. Fracture of the superior and inferior pubic rami bilaterally was diagnosed. (b) Drawing illustrates type IVa urethral injury.
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Figure 8b. (a) Retrograde urethrogram obtained in a 32-year-old man with bladder base injury following blunt trauma (type IVa urethral injury) shows extraperitoneal contrast material extravasation that extends from the elevated bladder base and surrounds the proximal urethra. Fracture of the superior and inferior pubic rami bilaterally was diagnosed. (b) Drawing illustrates type IVa urethral injury.
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Traumatic rupture of the female urethra is rare. Perry and Husmann (7) found type IV urethral injuries in 4.6% of women with pelvic fracture caused by high-speed motor vehicle accidents. Most reported cases have occurred in girls or young women. Rupture of the urethra should be suspected when blood is present at the external meatus or there is deep vaginal laceration (type IV injury). The urethra may be avulsed at or within 2 cm of the bladder neck (Fig 9).
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Figure 9a. Bladder neck urethral injury (type IV) in a 23-year-old woman. (a) Cystogram shows extraperitoneal contrast material extravasation (arrow) that extends from the bladder neck to the left underneath the balloon of a Foley catheter. (b) Cystogram obtained 2 minutes later shows progressive extraperitoneal contrast material extravasation. (c) Delayed contrast material-enhanced CT scan shows a laceration of the anterior wall of the urethra near the bladder neck (arrowhead), with extraperitoneal contrast material extravasation that extends to the diastatic pubic symphysis. Diastasis of the pubic symphysis and fracture of the left pubic ramus were diagnosed.
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Figure 9b. Bladder neck urethral injury (type IV) in a 23-year-old woman. (a) Cystogram shows extraperitoneal contrast material extravasation (arrow) that extends from the bladder neck to the left underneath the balloon of a Foley catheter. (b) Cystogram obtained 2 minutes later shows progressive extraperitoneal contrast material extravasation. (c) Delayed contrast material-enhanced CT scan shows a laceration of the anterior wall of the urethra near the bladder neck (arrowhead), with extraperitoneal contrast material extravasation that extends to the diastatic pubic symphysis. Diastasis of the pubic symphysis and fracture of the left pubic ramus were diagnosed.
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Figure 9c. Bladder neck urethral injury (type IV) in a 23-year-old woman. (a) Cystogram shows extraperitoneal contrast material extravasation (arrow) that extends from the bladder neck to the left underneath the balloon of a Foley catheter. (b) Cystogram obtained 2 minutes later shows progressive extraperitoneal contrast material extravasation. (c) Delayed contrast material-enhanced CT scan shows a laceration of the anterior wall of the urethra near the bladder neck (arrowhead), with extraperitoneal contrast material extravasation that extends to the diastatic pubic symphysis. Diastasis of the pubic symphysis and fracture of the left pubic ramus were diagnosed.
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Type V urethral injuries are caused by straddle injury and occur in the bulbous urethra (Fig 10). The bulbous urethra and corpus spongiosum are compressed between the hard object and the inferior aspect of the pubic bones. This compression may result in urethral contusion with an intact urethra or partial or complete rupture of the sump of the bulbous urethra. In general, a straddle urethral injury is not associated with a bone injury. If the Buck fascia remains intact, the extravasation is limited to the space between the Buck fascia and the tunica albuginea of the corpus spongiosum. If the Buck fascia is ruptured, extravasation of contrast material will be present within the confines of the Colle fascia at urethrography.
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Figure 10a. Anterior urethral injury following blunt trauma (type V urethral injury). (a) Retrograde urethrogram demonstrates complete disruption of the proximal bulbous urethra with extensive venous intravasation. (b) Drawing illustrates type V urethral injury.
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Figure 10b. Anterior urethral injury following blunt trauma (type V urethral injury). (a) Retrograde urethrogram demonstrates complete disruption of the proximal bulbous urethra with extensive venous intravasation. (b) Drawing illustrates type V urethral injury.
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Primary reconstruction of urethral disruption is preferred at 3–6 months, when the scar tissue at the urethral injury is stable and mature and associated injuries have been stabilized (8). Immediate open primary realignment of the urethral distraction is associated with a high rate of morbidity. However, selected patients suspected of having partial disruption can be treated by means of immediate "indirect," carefully performed endoscopically and fluoroscopically assisted stent placement with a urethral catheter (8). Late complications associated with posterior urethral injury include impotence, incontinence, stricture (Fig 11), and fistula (Fig 12), whereas those associated with anterior urethral injury include stricture and impotence.
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Figure 11. Stricture following traumatic bulbomembranous urethral distraction injury. Combined voiding cystourethrogram-retrograde urethrogram depicts both the proximal and distal ends of the stricture (straight arrows), which allowed measurement of the length of the stricture. Some continuing extravasation is also present (curved arrow).
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Figure 12. Prostatic urethrorectal fistula in a patient who sustained both a urethral disruption and a rectal injury in an automobile accident. Voiding cystourethrogram demonstrates a distal prostatic urethrorectal fistula (white arrow); the urethral stricture (black arrow) is just distal to the fistula. R = rectum.
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Penetrating Urethral Injuries
Penetrating urethral injuries from gunshot or knife wounds are uncommon and more commonly affect the anterior urethra (Figs 13, 14). Urethrography is indicated for all patients with penetrating penile injury because up to one-half of these patients have urethral injury. In general, penetrating injuries necessitate immediate surgical exploration and antibiotic therapy to contain superimposed infection. Gunshot wounds may destroy some urethral tissues, and patch or pedicle grafting may be required. Massive tissue injury is most suitable for staged surgical treatment. In general, knife wounds to the perineum can be treated with in situ repair of the lacerated bulbous urethra.
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Figure 14a. Urethral injury caused by insertion of a foreign body into the external meatus. (a) Conventional radiograph demonstrates a metallic pin (arrow) projected over the pubic bone. (b) Retrograde urethrogram obtained with use of a Brodny urethral clamp (b) demonstrates that the pin (arrow) lies in the posterior urethra and proximal bulbous urethra, with its distal end extending through the deformed bulbous urethral wall toward the perineum.
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Figure 14b. Urethral injury caused by insertion of a foreign body into the external meatus. (a) Conventional radiograph demonstrates a metallic pin (arrow) projected over the pubic bone. (b) Retrograde urethrogram obtained with use of a Brodny urethral clamp (b) demonstrates that the pin (arrow) lies in the posterior urethra and proximal bulbous urethra, with its distal end extending through the deformed bulbous urethral wall toward the perineum.
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Urethral Injury in Penile Fracture
Rupture of the corpus cavernosum from trauma to the erect penis ("penile fracture") is an uncommon injury and usually occurs during strenuous sexual activity. The patient experiences intense pain, and the penis becomes deformed and ecchymotic. Penile fracture is associated with urethral injury in 38% of patients, and retrograde urethrography is usually recommended to exclude a concomitant urethral injury (Fig 15). Magnetic resonance (MR) imaging is useful when the clinical presentation is atypical because it can allow accurate localization of the injury and assessment of the injured corpora cavernosa (9,10). Cavernosonography with the injection of 30% iodinated contrast material into the corpora cavernosum followed by fluoroscopy and spot radiography may show the exact site and extent of the tunica albunigea tear (11). This information may be useful because the site of a tunica albuginea tear may not be obvious at surgery. A urethrocavernous fistula may occur in the fractured penis and can be demonstrated at cavernosonography.
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Figure 15. Urethral injury in penile fracture. Retrograde urethrogram reveals contrast material extravasation in the penile urethra adjacent to the site of a corpus cavernosal injury.
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Postirradiation Injuries
Urethral complications following radiation therapy (external irradiation and radiation seed implant brachytherapy) include urethritis, urethral stricture, and urethral fistula (12). The latter is a serious complication of radiation treatment. Prostatic urethrorectal fistula has been reported to occur in 1% of patients after prostate brachytherapy for prostate cancer (Fig 16) (13).
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Figure 16a. Prostatic urethrorectal fistula following anterior low resection of the rectum and external beam radiation therapy for rectal carcinoma. Axial oblique (a) and sagittal (b) reformatted images generated from CT, performed with 2.5-mm-thick sections after the administration of contrast material into the bladder via a transurethral Foley catheter, demonstrate a prostatic urethrorectal fistula.
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Figure 16b. Prostatic urethrorectal fistula following anterior low resection of the rectum and external beam radiation therapy for rectal carcinoma. Axial oblique (a) and sagittal (b) reformatted images generated from CT, performed with 2.5-mm-thick sections after the administration of contrast material into the bladder via a transurethral Foley catheter, demonstrate a prostatic urethrorectal fistula.
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Urethral Disruption after Pancreas Transplantation
Bladder drainage of pancreatic graft exocrine secretions is a common technique in pancreas transplantation. One of the urologic complications of simultaneous kidney-pancreas transplantation with bladder drainage in male patients is urethral injury and disruption, with urinary extravasation occurring in 6% of cases (14,15). The urethral injury is attributed to activated proteolytic exocrine enzymes from the transplanted pancreas. Minor urethral trauma due to transurethral catheterization or cystoscopy appears to increase the risk of developing urethral injury related to pancreas transplantation. Urethral injury should be considered when dysuria persists and results of urine culture are negative. Retrograde urethrography is the imaging method of choice for making the diagnosis and typically demonstrates contrast material extravasation at the bulbous urethra and bulbomembranous junction (Fig 17). Short-term transurethral catheterization or suprapubic catheter drainage usually leads to resolution.
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Figure 17. Urethral disruption after pancreas transplantation. Retrograde urethrogram demonstrates contrast material extravasation from urethral disruption at the bulbomembranous junction. The contrast material surrounds the proximal bulbous urethra.
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Acquired Inflammatory Diseases
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Gonococcal and Nongonococcal Urethritis
Gonococcal urethritis is associated with the gram-negative diplococcus, Neisseria gonorrhoeae. Although gonorrheal infection has become less prevalent since the early 1980s, it remains the leading reportable sexually transmitted disease in adults in the United States. Patients with gonococcal urethritis usually present with purulent urethral discharge. However, nongonococcal urethritis is increasing in frequency. Chlamydia trachomatis is the most common pathogen of nongonococcal urethritis, accounting for 30%–50% of cases. Urethral discharge associated with nongonococcal urethritis is usually scant. The diagnoses of acute gonococcal or nongonococcal urethritis are usually made by means of clinical and laboratory findings. No imaging studies are necessary for noncomplicated urethritis. Complications associated with gonococcal urethritis are more common and more serious than those associated with nongonococcal urethritis and include urethral stricture, periurethral abscess, and periurethral fistula.
The typical urethrographic finding in gonococcal urethral stricture is an irregular urethral narrowing several centimeters long (Fig 18). An estimated 15% of men with gonococcal urethritis go on to develop stricture, with an interval of 2–30 years between infection and the onset of obstructive symptoms. With adequate antimicrobial treatment, however, the frequency of stricture associated with nongonococcal urethritis is believed to be extremely low (16). Hard fibrous scars are present at the distal portion of the bulbous urethra in 70% of patients. These scars are due to less effective flushing by urination and the preponderance of Littré glands in this area. Associated dilatation of Littré glands may be present at urethrography. If the proximal cone-shaped bulbar urethra appears to be narrowed, elongated, asymmetric, irregular, or absent, the stricture is seen to extend into the membranous urethra in more than 90% of cases (17). This radiologic finding is of prime importance to the urologist because surgical treatment may involve cutting the scar tissue and, consequently, the distal sphincter, which could result in iatrogenic incontinence. Urethroscopic or open surgical interventions are usually required to alleviate obstructive symptoms (eg, straining to void, weak stream, and a feeling of incomplete emptying of the bladder) secondary to urethral strictures. In selected cases, intraluminal stent placement may be effective for treating urethral stricture (18). (See also the section entitled "Strictures of the Urethra.")
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Figure 18. Gonococcal urethral stricture. Retrograde urethrogram reveals a segment of irregular, beaded narrowing in the distal bulbous urethra with opacification of the left Cowper duct (arrow).
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Periurethral abscess is a life-threatening infection of the male urethra and periurethral tissue and frequently a sequela of gonococcal infection, urethral stricture disease, or urethral catheterization. Periurethral abscess arises initially when a Littré gland becomes obstructed by inspissated pus or fibrosis. The most common infecting organisms are gram-negative rods, enterococci, and anaerobes. Pseudodiverticulum formation results from urethral communication with a periurethral abscess. Because the tunica albuginea of the penis prevents the dorsal spread of infection, the abscess tends to track ventrally along the corpus spongiosum, where it is confined by the Buck fascia. However, when the Buck fascia is perforated, there can be extensive necrosis of the subcutaneous tissue and fascia. Approximately 10% of periurethral abscesses drain spontaneously. Rapid diagnosis and treatment are essential. Imaging studies may be indicated if the diagnosis is not established clinically. An abscess that drains into the urethra may be demonstrated at urethrography (Fig 19). Ultrasonography (US) can demonstrate the presence of periurethral abscess, and CT and MR imaging are helpful for assessing the extent of the periurethral abscess and complications such as fasciitis and Fournier gangrene. Treatment consists of immediate suprapubic urinary drainage, wide surgical abscess debridement, and administration of appropriate antibiotics.
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Figure 19. Gonococcal urethral stricture with periurethral abscess. Retrograde urethrogram shows a long segment of irregular, beaded narrowing in the bulbous urethra with opacification of the Littré glands (arrow). Note the irregular periurethral cavity originating from the ventral aspect of the bulbous urethra.
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Urethroperineal fistulas are most often the consequence of a periurethral abscess. In general, the initial abscess cavity contracts by means of healing fibrosis, which leaves only the narrow fistulous tract from the urethra to the perineum. Consequently, urination usually occurs through the perineal fistulas, which results in the so-called "watering can perineum" (Fig 20) (19). Urethroperineal fistulas are usually the result of tuberculosis and schistosomiasis infections.
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Figure 20a. Stricture of the bulbous urethra with urethrocutaneous fistulas (watering can perineum). (a) Conventional radiograph reveals gas projected over the penile shaft. (b) Retrograde urethrogram reveals a long segment of irregular stricture involving the anterior urethra and membranous urethra with extensive fistulous tracts. Note the opacification of multiple Littré glands and the prostatic glands.
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Figure 20b. Stricture of the bulbous urethra with urethrocutaneous fistulas (watering can perineum). (a) Conventional radiograph reveals gas projected over the penile shaft. (b) Retrograde urethrogram reveals a long segment of irregular stricture involving the anterior urethra and membranous urethra with extensive fistulous tracts. Note the opacification of multiple Littré glands and the prostatic glands.
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Condyloma Acuminata
Condyloma acuminata are caused by viral infection and produce soft, sessile, squamous papillomas on the penile glans and shaft and the prepuce. Condyloma acuminata are termed venereal warts. Urethral involvement occurs in 0.5%–5% of male patients. On occasion, condyloma acuminata may extend to the prostatic urethra and bladder. The use of catheterization, instrumentation, and retrograde urethrography is not recommended because of the possibility of retrograde seeding. The diagnostic procedure of choice is voiding cystourethrography. However, the diagnosis is often not suspected until retrograde urethrography has been performed. The typical urethrographic findings are multiple papillary filling defects in the anterior urethra (Fig 21). Urethral lesions are treated with the instillation of podophyllin, thiotepa, or 5-fluorouracil into the urethra.
Tuberculosis
Tuberculosis of the urethra is very rare. Usually, genital tuberculosis is a descending infection and renal tuberculosis is evident. The prostate is involved in 70% of patients with genital tuberculosis. Prostatic abscess may rupture into any surrounding structure, which results in prostatorectal and prostatoperineal urethral fistulas. In the acute phase, there is urethral discharge with associated involvement of the epididymis, prostate, and other parts of the urinary system. The diagnosis is made at clinical examination, and administration of antituberculous agents should be initiated. In the chronic phase, diagnosis becomes difficult because patients present with obstructive symptoms secondary to urethral strictures. Tuberculous urethral strictures result in periurethral abscesses, which, unless treated, produce numerous perineal and scrotal fistulas. The end result is watering can perineum. Retrograde urethrography typically demonstrates an anterior urethral stricture associated with multiple prostatocutaneous and urethrocutaneous fistulas. Simultaneous fistulography may be useful for assessing the entire urethra because most contrast material exits the urethra through the urethroperineal fistulas, which may prevent visualization of the entire urethra.
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Strictures of the Urethra
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In general, the term urethral stricture refers to a fibrous scarring of the anterior urethra caused by collagen and fibroblast proliferation (17,20). Associated scar in the surrounding corpus spongiosum is known as spongiofibrosis. The scarring process can extend through the tissue of the corpus spongiosum and into adjacent structures. Contraction of this scar reduces the width of the urethral lumen. The causes of anterior urethral strictures may be inflammatory (eg, infectious urethritis, balanitis xerotica obliterans), traumatic (straddle injury, iatrogenic instrumentation) or congenital. Most urethral strictures are the result of infection, instrumentation, or other iatrogenic causes. The most common external cause of traumatic stricture is straddle injury. Inflammatory strictures associated with gonococcal urethritis have become less common despite the fact that gonococcus remains the most common sexually transmitted disease. Iatrogenic trauma to the urethra may result from pressure necrosis at fixed points in the urethra from indwelling catheters. Instrumentation-related strictures usually occur in the bulbomembranous region and, less commonly, at the penoscrotal junction.
Alternatively, posterior urethral stricture is often an obliterative process that occurs as a result of urethral distraction or disruption caused by either trauma or surgery. Posttraumatic posterior urethral stricture is often associated with resultant displacement of the urethral axis, which results in obliteration from intervening fibrosis. Iatrogenic stricture of the prostatic posterior urethra ("bladder neck contracture") usually occurs after transurethral resection of the prostate or open radical prostatectomy (21).
Retrograde urethrography is the primary method used to image anterior urethral stricture (17). Radiographic evaluation helps define the location, length, number, and degree of strictures as well as the periurethral abnormality—important factors for determining appropriate treatment. The length of the stricture will be underestimated if the patient is not placed in a steep oblique position for retrograde urethrography. More than one projection may be necessary to visualize the stricture. Sonourethrography is best used adjunctively to guide treatment planning in patients with known bulbous urethral strictures and has been reported to be more accurate than retrograde urethrography for estimating the length of urethral strictures (17,20). Periurethral fibrosis manifests at US as thickened, irregular, nondistensible tissue encroaching into the otherwise anechoic urethral lumen. When sonourethrography demonstrates posterior shadowing and a nondistensible lumen diameter of less than 3 mm during maximum retrograde distention, the changes of periurethral spongiofibrosis are considered to be severe. Spongiofibrosis is best treated with surgical resection.
In posterior urethral strictures following blunt trauma, simultaneous antegrade cystourethrography and retrograde urethrography are often required to determine the length of the urethral defect (Fig 11). MR imaging is considered to be the best ancillary imaging modality for assessing posttraumatic pelvic anatomy (22). Multiplanar T2-weighted MR imaging can help assess the position of the prostate and the amount of pelvic fibrosis and can help determine the length of the prostatomembranous defect by allowing measurement of the distance between the prostatic apex and urethral insertion into the proximal corpus spongiosum (22).
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Acquired Female Urethral Diverticula
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Abstract
LEARNING OBJECTIVES FOR TEST...
