UROGENITAL TRAUMA

Ultrasound Detection of Blunt Urological Trauma: A 6-Year Study
McGahan PJ, Richards JR, Bair AE, Rose JS
Department of Emergency Medicine, University of California, Davis, Sacramento, USA
Injury. 2005; 36: 762-70

• The objective of this study was to assess the utility of emergency ultrasonography in the detection of blunt urological injury. A retrospective review was conducted of all consecutive emergency blunt trauma ultrasonograms (US) obtained at a level I trauma centre from January 1995 to January 2001. Among the 4320 emergency ultrasonograms performed, 596 patients (14%) had intraabdominal injury and, of these, 99 patients (17%) had urological injuries. The sensitivity of ultrasound for all urological injuries was 67%, and specificity was 99.8%. For isolated urological injuries, sensitivity and specificity were 55.6 and 99.8%, respectively. Ultrasound was most accurate in the detection of grade III renal injuries, identifying 14/15 (93%), and 13 underwent laparotomy. For isolated urological injuries, 15 of 25 (60%) patients with a true-positive US underwent laparotomy compared to 3 of 20 (15%) with a false-negative US. Isolated urological injury was significantly associated with an ultrasonographic pattern of free fluid in the left upper quadrant and the left pericolic gutter (odds ratio=55.1; P < 0.001), followed by isolated fluid in the left pericolic gutter (odds ratio=8.6; P = 0.04). Although emergency ultrasonography is useful in the triage of patients with blunt urological trauma, it may miss significant urological injury requiring further intervention. As most renal injuries may be managed non-operatively, further studies such as contrast-enhanced CT or angiography should be obtained in the stable patient with suspected blunt urological injury.
  
  
• Editorial Comment
  Computed tomography with intravenous contrast is the gold standard when imaging the injured kidney. In this day and age, most CT scanners are quick and helical, and thus without separate delayed images, injuries to the collecting system or ureteropelvic junction can be missed. Although CT has its clear advantages, most of the world does not have the luxury of a CT scan available and working 24 hours a day, in every trauma center. An accepted alternative to CT has been a complete intravenous urogram, followed by possible angiography. This interesting paper by McGahan et al explores the value of US as a screening tool for renal injuries. The manuscript, however, is muddied by its statistics, wordiness, and nonstandard renal trauma grading scale.
  Arguably, ultrasound (US) is relatively cheap, safe, rapid, portable, and non-invasive method for imaging the abdomen. FAST (focused assessment with ultrasonography in trauma) has become an accepted method for evaluating the blunt trauma patient for possible intra-abdominal injuries. The value of US, however, is operator dependent. In properly trained hands, US have a sensitivity and specificity for detecting the presence of hemoperitoneum (suggesting intra-abdominal injury) as diagnostic peritoneal lavage (DPL). Ultrasound can be done at the bedside in the resuscitation area while simultaneously performing other diagnostic or therapeutic procedures. The indications for abdominal US are the same as for DPL.
  The true value to FAST is in the evaluation for blood in the pericardial sac, hepatorenal fossa, splenorenal fossa, and the pelvis. A second or control scan is then performed 30 minutes later. The control scan is done to detect progressive hemoperitoneum in patients with a slow bleeding rate. As a retroperitoneal organ, renal trauma blood and urine (free-fluid) are confined to Gerota’s fascia and the retroperitoneum. With kidney trauma associated free fluid is absent up to 1/2 the time. Free fluid noted with renal injuries is more likely to be free fluid from associated intra-abdominal injuries then from the kidney injury. This means that FAST must rely on parenchymal evaluation for grading of a renal injury. US imaging can be severely limited by obesity, subcutaneous air, and previous abdominal operations. Further limitations of US are its inability to distinguish between a urine leak and blood, and inability to reliably assess the vascularity of the kidney. Although not currently readily available, there is good promise that micro-bubble, contrast enhanced US may improve kidney parenchymal evaluation. Overall, FAST seems to be of value as a tool for triaging the unstable trauma patient, but when it comes to evaluating the stable kidney injured patient, US is not ready for prime time.

Dr. Steven B. Brandes
Associate Professor, Division of Urologic Surgery
Washington University in St. Louis
St. Louis, Missouri, USA