Tag Archives: CT

General

CT Cystography For Bladder Trauma

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Bladder injury after blunt trauma is relatively uncommon, but needs to be identified promptly. Nearly every patient (97%+) with a bladder injury will have hematuria that is visible to the naked eye. This should prompt the trauma professional to obtain a CT of the abdomen/pelvis and a CT cystogram.

The CT of the abdomen and pelvis will identify any renal or ureteral (extremely rare!) source for the hematuria. The CT cystogram will demonstrate a bladder injury, but only if done properly!

During most trauma CT scanning of the abdomen and pelvis, the bladder is allowed to passively fill, either by having no urinary catheter and having the patient hold it, or by clamping the catheter if it is present. Unfortunately, this does not provide enough pressure to demonstrate small intraperitoneal bladder injuries and most extraperitoneal injuries.

The proper technique involves infusing contrast into the bladder through a urinary catheter. At least 350cc of dilute contrast solution must be instilled for proper distension and accurate diagnosis. This can be done prior to the abdominal scan. Once the initial scan has been obtained, the bladder must be emptied and a focused scan of just the bladder should be performed (post-void images). Several papers have shown that this technique is as accurate as conventional retrograde cystography, with 100% sensitivity and specificity for intraperitoneal ruptures. The sensitivity for extraperitoneal injury was slightly less at 93%.

Bottom line: Gross hematuria equals CT of the abdomen/pelvis and a proper CT cystogram, as described above. Don’t try to cheat and passively fill the bladder. You will miss about half of these injuries!

Related posts:

Reference: CT cystography with multiplanar reformation for suspected bladder rupture: experience in 234 cases. Am J Roentgenol 187(5):1296-302, 2006.

Intraperitoneal bladder injury

Intraperitoneal bladder rupture

Extraperitoneal bladder

Extraperitoneal bladder injury

General

Blunt Trauma Radiographic Imaging Protocol

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Last year, we developed an evidence-based protocol for deciding what radiographic images to order in our blunt trauma patients. For some body regions, there is fairly good literature available for guidance (i.e. Canadian head and cervical spine rules). For other areas, there is not nearly as much.

We convened a small group of people, including trauma surgeons, emergency physicians, radiologists and a radiation physicist to combine the information into a practical tool. 

You can view or download the worksheet we use by clicking the link at the bottom of this post. The protocol has been in use for about 9 months, and has significantly decreased the use of higher radiation dose imaging (CT). As a result, there has been a small increase in the use of lower dose conventional imaging (plain spine studies), but no missed injuries. 

Tomorrow, I’ll write about the specifics of how this protocol has changed our ordering habits. Click here to view it.

Click here to download the Blunt Trauma Radiographic Imaging Protocol Worksheet

Click here to download a bibliography of the literature used to develop the protocol

General

Sonography In Place of CT For Pediatric Abdominal Trauma

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Pediatric blunt abdominal trauma is not common, but if present it has the potential to cause significant morbidity or mortality. Evaluation of the abdomen at the trauma center is crucial, and most trauma professionals are aware of the trade-offs in the use of CT scan in children (radiation exposure, need for sedation).

Ultrasound is widely available and allows for imaging of most areas of concern in the abdomen. Could sonography be used in place of CT in specific cases? Pediatric surgeons in Germany (who have been using ultrasound far longer than the US has) published a paper last year looking at their experience with children who were diagnosed with an intra-abdominal organ injury after blunt trauma. Their 7 year experience only produced 35 such children, and they were evaluated with examination and one or more serial FAST ultrasound exams. Equivocal results were scanned with CT.

They found that ultrasound was effective in diagnosing abdominal injury 97% of the time. Although 11 of the 35 children had subsequent CT scanning, it only changed management in one case. 

Bottom line: Obviously, this is a very small retrospective series, but it is provocative. The German pediatric surgeons go above and beyond the typical FAST exam in the US, using it for diagnostic purposes as well. Could a complete diagnostic ultrasound take the place of CT in select children in the US? Probably so, as they are very sensitive in detecting free fluid and solid organ injury. But what about blunt intestinal injury? I’ll review that tomorrow and sum up my thoughts on a possible algorithm.

Related posts:

Reference: Is sonography reliable for the diagnosis of pediatric blunt abdominal trauma? J Pediatric Surg 45(5):912-915, 2010.

General

Using CT To Diagnose Extremity Vascular Injury

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The traditional gold standard for diagnosis of vascular injury to the extremities has been a good physical exam plus conventional catheter angiography. However, using angiography always adds a layer of complexity and risk to patient care. The interventional team may not be immediately available after hours, there is typically a road trip within the hospital to deliver the patient for the study, and overall it is quite expensive.

With the advancements we have seen in CT angio techniques and scanner technology, some centers have been using computed tomography to evaluate for vascular injury. A few small retrospective studies have been done, but this month a larger prospective study was published.

Over a 20 month period, 635 patients with extremity trauma and a suspicion for vascular injury were entered into the study. A structured physical exam was performed, and any patient with “hard signs” of vascular injury were taken to the OR. 527 patients had no signs of vascular injury and were observed and released. The remaining 73 (most had soft signs of vascular injury) underwent CT angiography of the extremity.

The sensitivity and specificity of this test were 82% and 92%, respectively. Positive and negative results were nearly perfectly predictive. However, approximately 10% were inconclusive, usually due to bullet artifact or reformatting errors. These patients either underwent confirmatory conventional angiography or operation.

Bottom line: Angiography using multi-detector CT scanners is an excellent tool for evaluating potential extremity vascular trauma from penetrating trauma. The technology is available around the clock without a wait, and usually does not involve lengthy trips through the hospital. A good physical exam is imperative so patients with hard signs of injury can go straight to the OR. Equivocal studies must be evaluated further by conventional angio or an operation.

Reference: Prospective multidetector computed tomography for extremity vascular trauma. J Trauma 70:808-815, 2011.

General

Clinical Tip: The Flat Vena Cava in Blunt Trauma

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Trauma patients who are hypotensive in the Emergency Department can only be transported to one of two places: the operating room or the morgue. With rare exception, they should never be taken outside the department (e.g. CT scan) because of the fear that they may arrest in an area that is not conducive to efficient resuscitation.

Sometimes patients are initially stable but decompensate later. Since most stable blunt trauma patients end up in CT scan, perhaps there is some telltale sign that can predict later deterioration. A recent Japanese paper looked at the “flatness” of the inferior vena cava as seen on the abdominal CT scan as a predictor of hemodynamic decompensation in the first 24 hours.

A small cohort of 114 patients was used in this prospective study. The vena cava was evaluated at the level of the renal veins. The flatness of the IVC was determined by dividing the transverse diameter by the anteroposterior (AP) diameter. A flat IVC was defined as a transverse to AP diameter ratio of more than 4:1. The ratio in normal patients was about 2:1. See the figure for details.

Patients who had a flat IVC required significantly more blood transfusions, crystalloid infusions within 2 hours of admission, and were more likely to proceed to the OR within the first 24 hours of their hospital stay.

Bottom Line: Assuming that you are only taking stable blunt trauma patients to CT, the incidental finding of a flat vena cava should increase your paranoia levels and lower your threshold for ordering blood and getting the trauma surgeons involved. 

Reference: Predictive value of a flat inferior vena cava on initial computed tomography for hemodynamic deteroration in patients with blunt torso trauma. J Trauma 69(6):1398-1402, 2010.