Imaging of Disorders of the Male Urethra

Etiology

Urethral trauma may result from blunt, penetrating, or iatrogenic injury. The spectrum of urethral injuries includes contusion, partial or complete disruption, and urethral injury and may involve either the anterior or posterior urethral segment. Blunt anterior urethral injuries are commonly associated with perineal straddle injury, whereas posterior urethral injuries are usually a consequence of the shearing forces involved with a pelvic fracture. Penetrating injuries, including gunshot injuries, may involve both the anterior and posterior urethral segments.

Prevalence and Epidemiology

Blunt trauma causes the vast majority of injuries to the posterior urethra. Urethral disruption occurs in approximately 10% of pelvic fractures. Almost all membranous urethral disruptions related to blunt trauma have an associated pelvic fracture. Urethral injuries associated with pelvic fractures are much less common in females because of its shorter length and greater mobility in relation to the pubic arch. Anterior urethral injuries commonly occur as a result of straddle injuries and rarely follow anterior pubic rami and penile fractures.

Clinical Presentation

Inability to urinate, blood at the meatus, and a palpable bladder are the classic findings of urethral disruption. Other symptoms may include frank hematuria, a high-riding prostate on rectal examination, decrease in urinary stream, spraying or double stream, and postvoid dribbling. Inability to pass a urethral catheter may be the first indication of urethral injury. In delayed presentation, induration in the area of a posttraumatic stricture may be palpable.

Pathophysiology

The male urethra is anatomically subdivided at the level of the urogenital diaphragm into anterior (penile and bulbar portions) and posterior segments (membranous and prostatic portions), and the mechanism of urethral injury also may be classified along these lines. Posterior urethral injury is usually caused by a massive shearing force that results in concomitant pelvic fracture. Membranous urethral disruptions are associated with multiple organ injury, whereas anterior urethral injuries usually occur in isolation. Causes of anterior urethral injuries include straddle trauma crushing the immobile bulbous urethra against the pubic rami or a penile fracture leading to a laceration through the adjacent urethra. Iatrogenic injuries affect both anterior and posterior segments of the urethra.

Imaging

Radiography

Retrograde urethrography (RUG) is the study of choice in diagnosing urethral injuries. It is accurate, simple, and may be performed rapidly in the trauma setting. Extravasation of contrast agent from partial or complete disruption of the urethra is usually readily identified at urethrography. RUG permits assessment of the integrity of the anterior urethra and demonstrates gross extravasation from the posterior urethra. However, voiding cystourethrography (VCUG) may be required to completely evaluate the posterior urethra.

Several classifications of the anatomic site of urethral injury have been described. On the basis of RUG findings, Colapinto and McCallum described three types of posterior urethral injuries in 1977 (type I, II, and III injuries). Subsequently, in 1997, Goldman and associates proposed a new, expanded anatomic classification for the purposes of comparing treatment strategies and outcomes after blunt urethral trauma ( Figures 80-1 and 80-2 , Table 80-1 ).

TABLE 80-1

Classification of Male Urethral Injuries

From Goldman SM, Sandler CM, Corriere JN, Jr, McGuire EJ: Blunt urethral trauma: a unified, anatomical mechanical classification. J Urol 157:85–89, 1997.

Types of Urethral Injury	Findings
Type I	Posterior urethra stretched but intact; no extravasation
Type II	Partial or complete posterior urethral disruption with tear of the membranous urethra above urogenital diaphragm; extravasation into extraperitoneal pelvis
Type III	Partial or complete combined anterior and posterior urethral disruption with disruption of the urogenital diaphragm; extravasation into the extraperitoneal pelvis and perineum
Type IV	Bladder neck injury
Type IVA	Injury to the bladder base with periurethral extravasation simulating a bladder neck injury (may be difficult to distinguish from type IV injury radiologically)
Type V	Partial or complete pure bulbous urethral disruption, due to straddle injury