Excerpt from Urethra, Trauma

Synonyms, Key Words, and Related Terms: anterior urethral trauma, posterior urethral trauma, urethral injury, blunt trauma, straddle injury, pelvic fracture, urethral stricture, perineal injury, lower urinary tract, pelvic crush

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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.

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Pathophysiology: Trauma to the urethra can be attributed to guns, knives, surgical or urologic instruments, blunt trauma, straddle injuries, or penile fracture (Goldman, 1996; Hernandez, 1999; Koraitim, 1996; Tsang, 1992). 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 (Koraitim, 1996; Sandler, 2000). Most cases of anterior urethral trauma result from straddle injuries (Hernandez, 1999; Sandler, 2000).

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 (Koraitim, 1999). 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 (Koraitim, 1996). 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 (Koraitim, 1999; Sandler, 1998).

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 (Hernandez, 1999).

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 (Hernandez, 1999; Sandler, 1998). 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 (Sandler, 2000).

Penile fracture results only when the penis is erect, and the injury results in disruption of the corpora and tunica albuginea (Forman, 1989). Of the 180 cases of penile fracture that have been reported in litera .....