Diagnostic Imaging Pathways - Lower Urinary Tract Trauma

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Computed Tomography (CT) Cystogram

• Conventional CT of the abdomen / pelvis has a poor sensitivity of 50-60% for detecting blunt bladder injuries. 11,12 Its role in this setting is to identify other abdominal injuries
• The accuracy of CT for detecting and categorising bladder injuries can be greatly improved with a CT cystogram
• Indications for this study include gross haematuria, pelvic fractures or high clinical suspicion of bladder injury 13
• Recent studies support the use of retrograde filling of the bladder with dilute iodinated contrast. 19 Using this technique, the reported sensitivity for detecting bladder rupture ranges from 95% to 100% and the specificity is 100%. 13-16 These figures are comparable to conventional retrograde cystography 13
• For categorising the type of bladder injury, the accuracy of a CT cystogram for identifying extraperitoneal injury is similar to conventional cystography. However, the sensitivity is slightly lower for intraperitoneal injury (94% versus 100%) 13
• Multidetector CT with multiplanar reformation may help better localise the site of bladder rupture 16
• In order to minimise exposure to radiation, time and costs, CT cystograms can be performed as part of the screening abdomino-pelvic CT without the need for post-void images 1,5,13

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Computed Tomography (CT) Abdomen / Pelvis

• CT is more sensitive and specific in the diagnosis of renal trauma. It is the diagnostic modality of choice in imaging patients with suspected blunt renal trauma 1
• CT not only provides precise anatomic and functional information but also detects other coexisting intra-and extraperitoneal injuries at the same time 1
• MRI equals CT in correctly grading blunt renal injuries and detecting the presence and size of perirenal hematomas 1

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Bladder Trauma

• There is no sufficient Class I data supporting standards regarding evaluation of bladder and urethral trauma. Around 10% to 15% of patients with pelvic fractures sustain bladder injuries whereas more than 70% of bladder injuries are associated with pelvic fractures 1
• Bladder rupture is significantly associated with pubic symphysis diastasis, sacroiliac diastasis, and sacral, iliac and pubic rami fractures but not with isolated acetabular fractures 2,3
• The clinical indicators for bladder injury are
  • Suprapubic pain or tenderness
  • Inability to void, low urine output, clots in urine
  • Signs of major perineal trauma: swelling or hematoma, blood at the urethral meatus
  • Unresponsiveness, intoxication, altered sensation
  • Free intraperitoneal fluid on CT scan or ultrasound
  • Pre-existing bladder outlet obstruction, bladder surgery, or bladder abnormality
  • Abdominal distention, hypoactive bowel sounds
  • Increased serum BUN and/or creatinine
• When should bladder imaging be considered a priority in blunt trauma patient?
  • Current literature suggests that immediate imaging is essential only in the event of gross hematuria with pelvic fracture 4
  • In atypical patients without the classic combination of pelvic fracture and gross hematuria, the presence of clinical indicators should guide one to screen for bladder injury
  • In the absence of the clinical predictors, immediate bladder imaging is not warranted 4

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Microhaematuria in Bladder Trauma

• While grossly clear urine in a trauma patient without a pelvic fracture virtually eliminates the possibility of a bladder rupture, between 2-10% of patients with bladder rupture may demonstrate microhaematuria or have no haematuria at all 5,6
  • Cass et al. describes a large series of patients with bladder injuries, in which 80% of the patients with rupture had gross hematuria. However, six patients with <30 red blood cells/high power field (RBC/HPF) had bladder ruptures, and 16 patients without any haematuria also had bladder ruptures 6
  • However, other studies by Morgan et al. and Avey et al. found no bladder ruptures in patients with <25 RBC/HPF and <30 RBC/HPF, respectively 2,7
• A recent prospective study of blunt trauma patients showed that bladder imaging is required for gross hematuria, even when no pelvic fracture is suspected, but is unnecessary for microscopic hematuria 8

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Emergency Retrograde Urethrogram

• The presence of blood at the urethral meatus should preclude any attempts at urethral instrumentation until the entire urethra is adequately imaged. Often a suprapubic catheter is inserted and a retrograde urethrogram is performed when appropriate 5
• Radiologic evaluation with a cystogram and post-wash out film and a retrograde urethrogram allow immediate diagnosis of bladder and urethral injury 17
• Retrograde urethrogram should be performed in all patients with fracture of sacroiliac joint and pubic ramus in addition to perirectal or scrotal hematoma, blood at the meatus, and/or high riding prostate. Patients with urethral injuries examined less than 1 hour after injury may not show physical findings 18

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