Urethral Rupture

Injury to urethra is usually associated with severe pelvic trauma. Most posterior urethral injuries are associated with blunt pelvic trauma due to motor vehicle accident or fall from height. Anterior urethral injuries commonly due to straddle injuries[1]. Among male patients with pelvic fractures the incidence of urethral rupture is about 25%. Urethral injuries due to trauma in women are rare [1]. Urethral injuries are classified into three categories by Colapinto and Mccallum (1977) [2] and later it was expanded and reclassified to include bladder injuries that involve and simulate anterior and posterior urethral injuries by Goldman et al [2,3]. Male posterior urethra is encased in protective structure the rigid pelvis and damage to posterior urethra occurs when the supportive structure is disrupted [1]. The potential for urethral trauma has been classified according to the severity of pelvic fracture. The three categories of pelvic fractures are no risk, low risk and high risk. The “no risk” injuries include isolated fractures of acetabulum, ilium or sacrum. Low risk group include single ischiopubic ramus or ipsilateral rami fracture and “high risk” injuries include straddle or malgaigne fractures [1]. The classical clinical signs of urethral injury are blood at urethral meatus, a high riding prostate on digital rectal examination and inability to void. Male urethra is divided into four anatomically identified parts as prostatic, membranous, bulbous and pendulous urethra. Prostatic urethra is approximately 3cm in length and extends from base of the bladder up to external sphincter. Membranous urethra situated immediately distal to prostatic urethra and surrounded throughout its length by urogenital diaphragm (UGD). In a 45 degree oblique radiograph, a line joining the junction of upper and middle thirds of both inferior pubic rami helps to localize the approximate position of membranous urethra. Bulbous urethra lies between the external sphincter and peno - scrotal junction. Pendulous or the penile urethra is the mobile portion of the urethra distal to bulbous urethra [4]. In 1977 Colapinto and McCallum proposed a classification of posterior urethral injury based on urethrographic patterns of contrast extravasation [2]. The categories are, Type 1 injury; posterior urethra is stretched and elongated but intact. The prostate and bladder are displaced superiorly due to disruption of puboprostatic ligaments and resulting hematoma. Type 2 injury; disruption of urethra above the urogenital diaphragm (UGD) preserving the membranous urethra. Type 3 injury; damage to membranous urethra with extension of injury into bulbous urethra and/or disruption of UGD [2]. Gold standard technique for diagnosing urethral rupture is retrograde urethrography and it is described as extravasation of contrast material into pelvic extraperitoneal space or the perineum. Extravasation of contrast material into the pelvic extraperitoneal space without extending into perineum indicates type 2 injury. Contrast extravasation into the perineum without an anterior urethral rupture is due a disruption of UGD and it indicates a type 3 injury [2]. CT scan is the accepted first line method of imaging for abdominopelvic trauma and some CT features may help to identify a posterior urethral injury. CT signs are categorized into features that are specific for a type of injury and features that are not type specific but indicate a urethral injury [3]. CT signs that indicate type 1 injury are elevation of prostatic apex above the UGD and distortion of prostatic contour and obliteration of preprostatic fat space by hematoma. Type 2 injuries are recognized by extravasation of urinary tract contrast material that does not extend beyond the UGD and in Type 3 injury urinary contrast extravasation seen at or below the UGD (this contrast material either originated from prior retrograde urethrogram study or patients who did not have a Foley catheter and voided on table during the examination). CT features to distinguish Type 2 and Type 3 are not very sensitive as the contrast material may tract along the fascial planes and be present above or below the UGD, which could represent a Type 2 or Type 3 injury. CT sings that indicate urethral injury but not type specific are distortion and obliteration of UGD fat plane, hematoma of ischeocavernosus muscle, distortion of prostatic contour, distortion and obscuration of bulbocavernosus muscle and hematoma of obturator internous muscle [3]. Retrograde urethrography confirms the findings of CT and identify the type of injury. Urethral injuries should be identify at an early stage and treated according as they can increase the morbidity. The three most common morbidities identified are stricture, incontinence and impotence [1,3].