Epidemiology

Approximately 10% of trauma patients sustain injury to the genitourinary system. The majority of these injuries (approximately 80%) are the result of a blunt trauma mechanism. Timely identification and management of genitourinary injuries can minimize the associated morbidity, which may include impairment of urinary continence and sexual function. Identification of injury depends on a stepwise evaluation with consideration of the mechanism of injury, pertinent findings on physical examination, urinalysis, and appropriate diagnostic imaging performed in the correct sequence.

Pathophysiology

Anatomically, the genitourinary system is divided into lower and upper tracts. This division is clinically important because specific mechanisms tend to injure different parts of the genitourinary system. The lower genitourinary tract consists of the external genitalia, urethra, and bladder (Figs. 82.1 and 82.2). The upper genitourinary tract consists of the ureters and kidneys.

Fig. 82.1 Sagittal view of the normal male pelvis.

Fig. 82.2 Sagittal view of the normal female pelvis.

External Genitalia

The male external genitalia consist of the penis, scrotum, testicles, and ejaculatory complex. The female external genitalia consist of the vagina and vulva; the latter includes the labia majora, labia minora, and clitoris.

Injuries to the external genitalia may occur by blunt or penetrating mechanisms or by circulatory compromise induced by constricting devices applied either accidentally (as in the case of a hair tourniquet) or intentionally (e.g., to enhance sexual performance and pleasure). Additionally, the skin of the penis, scrotum, or labia may become ensnared by a metal zipper. Blunt trauma mechanisms include a kick or other direct blow to the genitals, falls, and straddle injuries. Penile fracture is a blunt injury that occurs when an erect penis is bent suddenly and forcefully, with rupture of the tunica albuginea of one or both of the corpora cavernosa. This injury occurs most commonly during sexual intercourse when the penis slips out of the vagina and strikes the partner’s pubis or perineum, but it may also occur during masturbation. Significant injury to the external genitalia may accompany pelvic fractures. Penetrating injuries may be inflicted by gunshot wounds, knives, or other sharp objects.

Urethra

The male urethra is divided into anterior (bulbous and pendulous) and posterior (prostatic and membranous) portions. Traditionally, this division has been described at the level of the urogenital diaphragm; however, recent work has questioned the existence of this structure, as classically taught.¹^–³ Regardless, the weakest point of the posterior urethra is the bulbomembranous junction, and it is the area where the majority of posterior urethral disruptions occur.¹

Injuries to the anterior urethra occur from direct blows, straddle injuries, or instrumentation or in conjunction with a penile fracture (Fig. 82.3). By contrast, posterior urethral injuries usually occur in the setting of significant pelvic fractures, often caused by motor vehicle collisions (Fig. 82.4). Penetrating injuries may be inflicted by gunshot wounds, knives, or other sharp objects. Urethral injuries are much less common in women because the female urethra is short and relatively mobile and lacks significant attachment to the pubis.

Fig. 82.3 Anterior urethral injury.

Note the extravasation of blood at the injury site (arrow) with dissection into tissues of the scrotum and perineum.

Fig. 82.4 Posterior urethral injury.

Note the displacement of the prostate by the hematoma at the site of injury (arrow).

Overall, urethral disruption accompanies pelvic fracture in approximately 5% of cases in women and up to 25% of cases in men.^1,⁴ However, the risk for urethral injury varies with the type of pelvic fracture. High-risk fractures include concomitant fractures of all four pubic rami (straddle fractures; Fig. 82.5) or fractures of both ipsilateral rami accompanied by massive posterior disruption through the sacrum, sacroiliac joint, or ilium. Low-risk injuries include single ramus fractures and ipsilateral ramus fractures without disruption of the posterior ring. The risk for urethral injury approaches zero with isolated fractures of the acetabulum, ilium, and sacrum.¹ Posterior urethral disruption occurs when a significant pelvic fracture causes upward displacement of the bladder and prostate. Avulsion of the puboprostatic ligament is followed by stretching of the membranous urethra and subsequent partial or complete disruption at the anatomic weak point, the bulbomembranous junction.¹

Fig. 82.5 Straddle pelvic fracture.

Note the concomitant fractures of all four pubic rami. This injury confers a high risk for urethral disruption.

Bladder

When empty, the bladder lies along the floor of the pelvis, where it is relatively protected unless the force of an injury fractures the bony pelvis. When distended by urine, the bladder may extend up to the level of the umbilicus, where it is vulnerable to blunt force trauma inflicted on the lower part of the abdomen. The weakest and most mobile area of the bladder is at the peritoneal surface of the dome.

Blunt force bladder injuries are seen with lower abdominal trauma and in conjunction with pelvic fractures, often resulting from a motor vehicle collision. They are classified as contusions, intraperitoneal rupture, or extraperitoneal rupture. Contusions are partial-thickness injuries to the bladder wall without rupture. Intraperitoneal rupture is caused by a blunt force injury to the lower part of the abdomen in a patient with a full bladder, which results in rupture at the bladder dome followed by extravasation of urine into the peritoneal cavity. Extraperitoneal rupture occurs most often in association with a pelvic fracture, and the injuring force causes rupture at the anterior or anterolateral wall. In other cases, bony fragments from the pelvic fracture impale the bladder and result in extraperitoneal rupture. Penetrating injuries may be inflicted by gunshot wounds, knives, or other sharp objects.

Ureters

The ureters course distally along the psoas muscles and enter the bladder posteriorly and inferiorly at the trigone.

Ureteral injury is rare and occurs in less than 1% of all genitourinary injuries.⁵ In adults, penetrating injuries account for approximately 90% of cases, most commonly inflicted by gunshot wounds.⁶ In children, the most common mechanism is blunt avulsion at the ureteropelvic junction as a result of a motor vehicle collision or a fall from a height. This injury pattern is thought to be due to the increased mobility of the pediatric vertebral column, which allows extreme hyperextension that results in upward displacement of the kidney and separates it from the relatively immobile ureter.

Kidneys

The kidneys lie in the retroperitoneal space and are protected by the lower ribs, the back musculature, and perinephric fat. The right kidney extends lower than the left one because of the presence of the liver.

Significant force is required to injure the kidney. Motor vehicle collisions, falls, direct blows, and lower rib fractures are common mechanisms. Significant decelerating force may cause avulsion of the renal pedicle. In children, bicycle accidents represent a prominent mechanism of renal injury.⁷ Penetrating injuries may be inflicted by gunshot wounds, knives, or other sharp objects.

Presenting Signs and Symptoms

External Genitalia Injuries

Blunt scrotal trauma may result in superficial ecchymosis and swelling or testicular rupture, torsion, or displacement. In testicular rupture, the tunica albuginea is disrupted. Even in the absence of testicular rupture, blood or fluid may accumulate between the tunica albuginea and tunica vaginalis and result in a hematocele or hydrocele, respectively. Testicular torsion disrupts the vascular supply and causes ischemia. Testicular displacement occurs when the testicle is forced from the scrotum, usually into the peritoneal cavity. Physical examination may be limited because of pain and swelling.

Penile fracture is often accompanied by an audible snapping sound and is followed immediately by severe pain, detumescence, swelling, and ecchymosis. The corpus spongiosum is involved in 20% to 30% of cases, and urethral injury occurs in 10% to 20%. If the Buck fascia remains intact, the swelling and ecchymosis are confined to the penile shaft. If not, blood and urine may dissect into the scrotum, perineum, and suprapubic spaces.^8,⁹

In patients with penetrating mechanisms, a careful and complete physical examination should be conducted to search for associated or additional occult injuries. In one series, gunshot wounds involving the penis were associated with injury to other organ structures in 80% of cases.¹⁰ Violation of the corpora cavernosa requires operative intervention and is heralded by an expanding penile hematoma, significant bleeding from a wound to the penile shaft, or a palpable corporal defect.

Injuries to the female genitalia are often associated with pelvic fractures. Important mechanisms include physical or sexual assault, consensual intercourse, and penetrating injuries. In the presence of a pelvic fracture or blood at the introitus, meticulous vaginal examination is mandated. Complications of missed vaginal injuries include infection, fistula formation, and significant hemorrhage.^11,¹² In one series, 25% of women sustaining injury to the external genitalia required red blood cell transfusion because of blood loss from the genital injury alone.¹¹

Urethral Injuries

In blunt trauma, the signs and symptoms of urethral injury include blood at the urethral meatus, gross hematuria, inability to void, absent or abnormally positioned prostate on digital rectal examination, or ecchymosis or hematoma involving the penis, scrotum, or perineum. In penetrating trauma, urethral disruption should be suspected when the injury trajectory lies in proximity to the course of the urethra.

Bladder Injuries

The vast majority of blunt bladder injuries are accompanied by gross hematuria, significant pelvic fracture, or both. In general, the diagnosis may be excluded clinically when both are absent. Bladder injury may occur with any pelvic fracture but is more likely with fractures of the anterior arch or when all four pubic rami are fractured. A minority of patients will have a pelvic fracture with microscopic hematuria. Additional signs and symptoms include lower abdominal pain or tenderness and inability to void. In patients with penetrating trauma, bladder rupture should be evaluated when the injury trajectory lies in proximity to the bladder.

Ureteral Injuries

Hematuria (gross or microscopic) is not a reliable predictor of ureteral injury because the findings on urinalysis are normal approximately 25% of the time.^7,¹³ The diagnosis is frequently missed on the initial evaluation because the signs and symptoms are minimal and nonspecific. Delayed findings include fever, flank pain, and a palpable flank mass (urinoma). Ureteral injury should be considered in patients with any penetrating injury that has a trajectory in proximity to the ureter.