eMedicine Specialties > Radiology > Genitourinary

Urethra, Trauma

Author: J Kevin Smith, MD, PhD, Professor of Abdominal Imaging, Vice Chair for Veterans Affairs, Department of Radiology, University of Alabama at Birmingham; Chief of Service, Department of Radiology, Birmingham Veterans Affairs Medical Center
Coauthor(s): J Scott Schauberger, BS, University of Alabama at Birmingham School of Medicine; Philip Kenney, MD, Professor of Radiology and Chairman, Department of Radiology, University of Arkansas for Medical Sciences
Contributor Information and Disclosures

Updated: Apr 16, 2009

Introduction

Background

Injury to the urethra is usually associated with severe pelvic trauma in males. The results of such an injury can have enduring consequences that include stricture, impotence, and incontinence.¹

Pathophysiology

Trauma to the urethra can be attributed to guns, knives, surgical or urologic instruments, blunt trauma, straddle injuries, or penile fracture.^2,3,4,5 Most male posterior urethral injuries, however, are the result of blunt pelvic trauma most often associated with a vehicular accident or a fall from a height.^4,6 Most cases of anterior urethral trauma result from straddle injuries.^3,6

The male posterior urethra is entirely encased within the rigid pelvis, a protective structure that must be disrupted before the posterior urethra can be damaged by blunt external trauma.⁷ The potential for urethral trauma is thus influenced by the extent of the pelvic injury, and this potential has been classified as no risk, low risk, and high risk.⁴ Examples of no risk injuries include isolated fractures of the acetabulum, ilium, or sacrum; low-risk injuries include single ischiopubic ramus or ipsilateral rami fractures; and high-risk injuries include straddle fractures or Malgaigne fractures. Overall, disruption of both the anterior and posterior sides of the pelvic ring introduces greater risk of urethral trauma.

Damage of the posterior urethra is thought to occur as its support mechanism becomes disrupted. As soft tissue becomes compressed, the puboprostatic ligament ruptures, disconnecting the prostate from the anterior pubic arch. This mobilizes the prostate and bladder. In many cases, a hematoma develops inferior to the prostate from sheared periprostatic vessels. The prostate is then driven cephalad by the growing hematoma. The posterior urethra, however, is firmly attached to the pubic arch by the perineal membrane. The resultant shearing force stretches or ruptures the urethra in varying locations as described by radiographic findings.^7,8

Anterior urethral injuries are seen in a small minority of patients because of the mobility of the anterior urethra compared with the posterior urethra. Most cases are the result of straddle incidents, in which the patient falls on the crossbar of a bike or the top of a fence. Force from the structure on the perineum compresses the corpora spongiosum and bulbous urethra against the pubic symphysis, disrupting the urethra. In some mild cases, the resulting injury will go untreated; however, a stricture develops over time. The patient presents at this time with an inability to void. In some cases, the patient is unaware of the relationship to the past straddle injury.³

If the Buck fascia remains intact, the injury will be limited to the space between the fascia and the tunica albuginea. If, however, the Buck fascia is also disrupted, a hematoma may spread within the confines of the Colles fascia.^3,8 Thus, blood or contrast material extravasation may extend to the scrotum, perineum, or anterior abdominal wall. Contrast would not extend into the thigh because of the insertion of the Colles fascia into the fascia lata of the thigh.⁶

Penile fracture results only when the penis is erect, and the injury results in disruption of the corpora and tunica albuginea.⁹ Of the 180 cases of penile fracture that have been reported in literature, only 10% of these cases have reported accompanying urethral disruption. Of these, only 3 cases have reported a complete urethral tear.⁵

Among women, the most common types of urethral injuries described are longitudinal tears and avulsion-distraction injuries, with the later attributed to more severe lateral compressive pelvic trauma.^7,10

Frequency

United States

Most posterior urethral trauma cases in males result from pelvic injury. Among male pelvic traumas, the reported frequency of urethral injury varies widely from 1-25% with an average of approximately 10%. Urethral injury in women with pelvic trauma is considered a less common event; however, some studies have reported incidences as high as 4-6%.⁷ Anterior urethral trauma is thought to occur less frequently due to its higher mobility, but the frequency of occurrence has not been established.

Mortality/Morbidity

The 3 most common morbidities associated with urethral trauma are stricture, incontinence, and impotence.

The incidence of these morbidities is dependent on the severity of the injury and the method of management and repair.

Sex

Urethral traumas are more frequent in the male population than in the female population.^6,10 This difference is attributed to the higher elasticity, shorter length, and fewer attachments of the female urethra.¹⁰ Approximate male-to-female ratios are unknown, because inconsistency exists in diagnosing female urethral trauma.

Among women, the most common types of urethral injuries described are longitudinal tears and avulsion-distraction injuries, with the later attributed to more severe lateral compressive pelvic trauma.^7,10

Age

An age-linked risk of urethral injury associated with pelvic fracture has been shown for children younger than 15 years. The suggested cause for this pattern is the difference in pelvic fracture severity seen between children and adults. For pelvic fractures in children, approximately 56% of cases are at high risk for urethral injury. Among adults, only 24% are at high risk for urethral injury.⁴

Anatomy

Historically, the male urethra has been divided into anterior and posterior parts, which are demarcated at the urogenital diaphragm. The proximal posterior urethra begins at the interface with the bladder, the internal urethral orifice, and the prostatic urethra. The prostatic urethra is entirely contained within the prostate and is continuous with the membranous urethra at the prostatic apex inferiorly. A principal support structure, the puboprostatic ligament, firmly attaches the prostate to the anterior pubic arch. This anatomy is important for locking the posterior urethra and prostate into their relative positions within the extraperitoneal pelvis.

The membranous urethra is located within the anterior tip of the urogenital diaphragm and becomes the proximal portion of the anterior urethra after passing through the perineal membrane. The principal mechanism of continence, the external urethral sphincter, is located within the urogenital diaphragm around the membranous urethra. The Cowper glands are also located within the urogenital diaphragm adjacent to the urethra.

The bulbous urethra, a swelling in the proximal anterior section, travels within the proximal corpus spongiosum and is continuous with the penile urethra. The ducts to the Cowper glands drain into the bulbous urethra. The penile or pendulous urethra extends the length of the penis where it ends as the fossa navicularis and urethral meatus.

Presentation

A diagnosis of urethral trauma should be investigated in the presence of pelvic fracture, straddle injury, penetrating trauma in the vicinity of the urethra, or penile fracture. While there are no findings specific for urethral trauma, there are many that suggest its presence. Findings can include blood at the urethral meatus, gross hematuria, an inability to spontaneously void, and a high riding prostate on rectal examination.^6,7,8,11

For many patients with urethral injury, extravasation of blood contained within different fascial planes is also present. On examination, patients with injuries to the urethra distal to the urogenital diaphragm and not contained by the Buck fascia typically have a butterfly hematoma, which forms as blood collects in the superficial perineum.³ Scrotal enlargement is also common in this injury, as extravasated fluids are bound by only the Colles fascia. For patients with anterior urethral trauma with extravasation confined by the Buck fascia, edema and ecchymosis of the penile shaft is common.⁶ In some cases, however, a hematoma is not seen until at least an hour after injury.⁷

Preferred Examination

For most patients with widespread acute trauma, CT scanning is performed as an initial diagnostic tool.^12,13 However, these scans are not traditionally used for diagnosing urethral trauma. On the basis of new research, however, it is possible that in the future CT could be used as initial screen for urethral injuries.^12,14,15

If any of the clinical findings listed above are present, the possibility of urethral trauma should be properly investigated by retrograde urethrography (RUG).^7,8 This should always be done prior to the insertion of a urethral catheter.

In the past, diagnostic catheterization was used to check for urethral disruption. This has been universally dismissed as an acceptable diagnostic tool.⁷ A urethral catheter risks converting a partial urethral tear into a complete urethral disruption, it can increase the extent of hemorrhaging, and it increases the possibility of contaminating a sterile hematoma.16⁶ If, however, a urethral catheter is properly in place prior to evaluation for urethral trauma, it should not be removed in order to perform urethrography. In such a case, a pericatheter urethrogram may be obtained.

After a diagnosis of urethral trauma has been made, management and repair can be planned with the possible aid of other imaging modalities, such as MRI and ultrasonography. MRI has some utility in planning surgical approach for posterior urethral disruptions, and ultrasonography has been used at times to aid in the repair of urethral trauma.^{9,16,17,18,19}

Limitations of Techniques

While RUG provides clinically valuable information on the presence, location, and severity of urethral extravasation, it provides limited information about the details of surrounding soft tissue damage. Furthermore, imaging of the proximal urethra can occasionally be inadequate. This is usually caused by subpar contrast-agent filling of the proximal urethra or by gross extravasation of contrast blocking visualization of the proximal urethra.¹⁷

In contrast, MRI has proven clinical utility in its ability to define damage to soft-tissue neighboring the urethral trauma. Alone, however, MRI should not be used to investigate urethral extravasation or to define urethral trauma as partial or complete.^16,17

Differential Diagnoses

Other Problems to Be Considered

Urethral stricture
Penile fracture
Bladder-neck injury
Prostate injury
Pelvic fracture

• Search for CME/CE on This Topic »

• Urethral Trauma (Urology)
• Ureteral Stricture (Urology)
• Abdominal Trauma, Blunt (Trauma)
• Critical Care Considerations in Trauma (Trauma)

• Kidneys and Urinary System Center
• Bladder Control Problems Symptoms
• Bladder Control Problems Causes
• Bladder Control Problems Overview
• Bladder Control Problems Treatment
• Understanding the Male Anatomy

• EAU 2009: Interns Receive Little to No Training in Proper Insertion of Urethral Catheters
• Survival Advantage in Trauma Centers Not Due to Rapid Intervention
• Mild Trauma Associated With Chronic Headaches in Returning Soldiers

• The Impact of Childbirth on the Pelvic Floor
• Urinary Incontinence in the Childbearing Woman
• Fractured Penis: a Review

• Trauma Resource Center
• Disaster Preparedness and Aftermath Resource Center