A 45-year-old man is brought to the emergency department after a high-speed motor vehicle collision. He has lower abdominal pain and a sensation of bladder fullness, but has been unable to urinate since the collision. Trauma work-up is notable for bruising over the chest and suprapubic tenderness. CT scan of the chest, abdomen, and pelvis reveals rib fractures and a pelvic fracture. Which of the following portions of the urogenital tract is most likely injured in this patient?
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This patient with a pelvic fracture and difficulty voiding despite a sensation of bladder fullness most likely has a posterior urethral injury. Urethral injuries most commonly occur in men because of their longer urethral length and are divided into anterior and posterior injuries:
The anterior urethra (penile and bulbus segments) is protected from indirect forces by its relative mobility. These regions are typically injured secondary to urethral instrumentation or direct blunt force trauma (eg, straddle injury) (Choices D and E).
The posterior urethra (membranous and prostatic segments) is physically fixed to the pelvic bones by supportive structures (eg, sphincter and facial layers of urogenital diaphragm, puboprostatic ligament). Traumatic pelvic fracture can result in upward displacement of these segments, resulting in excessive stretching of the membranous urethra which often tears at the bulbomembranous junction (anchored distally by the thick perineal membrane).
Urethral disruption typically manifests with blood at the urethral meatus. Tearing at the bulbomembranous junction also allows urine and blood to extravasate into the potential spaces under the prostate and bladder, displacing them superiorly (eg, high-riding prostate). Significant damage can also impact urethral patency, leading to obstruction of bladder outflow (inability to void, suprapubic tenderness, bladder fullness).
(Choice A) Anterior bladder wall injury is common with pelvic fractures and is usually associated with extraperitoneal urine leakage. Superior bladder wall rupture often occurs with abdominal trauma when the bladder is full and results in intraperitoneal urine leakage. However, this patient's sensation of bladder fullness but inability to void makes urethral injury more likely.
(Choice B) The prostatic urethral segment is structurally supported by the surrounding prostate tissue and is less likely to be injured than the membranous urethra.
Educational objective:
Pelvic fracture are frequently associated with injury to the posterior urethra, in particular the bulbomembranous junction. Inability to void despite a full bladder sensation, a high-riding boggy prostate, and blood at the urethral meatus are clinical findings suggestive of urethral injury.