Contrast Ultrasound in Trauma

Contrast FAST byte


Blunt abdominal trauma: role of contrast-enhanced ultrasound (CEUS) in the detection and staging of abdominal traumatic lesions compared to US and CE-MDCT

La Radiologica Medica February 2015 - Pubmed Link


Take Home Points

1. In mild stable isolated abdominal trauma, contrast enhanced ultrasound was 96% sensitive and 99% specific for organ injuries compared to CT.

2. Contrast enhanced ultrasound has greater sensitivity for intrabdominal free fluid and solid organ injury identification compared to non-contrast enhanced ultrasound.


Background

High energy traumas usually will undergo pan-scanning with contrast enhanced multidetector CT imaging (CE-MDCT). Lower energy injuries may not need CT since it poses risks from radiation and IV contrast administration. The FAST (focused assessment with sonography for trauma) is commonly used to assess for free peritoneal fluid, which in the setting of trauma is assumed to be due to traumatic intraabdominal injury. Ultrasound has good sensitivity for free fluid, but low sensitivity for solid organ traumatic lesions. Prior studies have shown that contrast-enhanced US (CEUS) is more sensitive than non-contrast US for detected solid organ injuries. This uses stabilized microbubbles to “light up” areas of blood flow. It also makes it possible to grade the traumatic lesions.


Question

How does CEUS compare to MDCT for staging and detection of traumatic abdominal lesions in low energy isolated abominal trauma?


Population

Single trauma center

Inclusion:

  • Low energy isolated abdominal trauma

  • Hemodynamically Stable SBP > 90, HR <100, RR< 20

  • Yellow or Green START catergory


Who did the scans?

Radiologists with at least 5 years’ experience in emergency radiology and specific expertise in trauma imaging


Design

Retrospective review of consecutive patients over 7 years, single center

Multi detector Computed Tomography (MDCT) was gold standard to calculate sensitivity, specificity, PPV, NPV, accuracy for both number of lesions and presence of free peritoneal fluid of US and CEUS.

Also looked for sensitivity of CEUS grading of lesions (by American Association for the Surgery of Trauma) and identification of active bleeding


Intervention

All patients underwent FAST with regular ol’ ultrasound and also CEUS (second generation contrast agent)

All patients underwent MDCT (16 slice) with IV contrast within 1 hr of CEUS - standard arterial (40-50s delay) and venous (80-100 s) protocol, +/- late phase (3-15 min) if collections identified


Scan

The FAST exam - How to do a FAST at 5 minute Sono

In this Study:

Curvilinear 4 MHz probe

Software containing “contrast-pulse sequencing” - detects microbubbles

  1. 2.4 mL of contrast in 18 guage antecubital vein, flushed with 5-10 mL saline

  2. Scan RUQ (right kidney and liver) for 1-3 minutes

  3. Second 2.4 mL of contrast, flushed

  4. Scan LUQ (left kidney and spleen) for 3-4 minutes

US: looked for peritoneal fluid but also parenchymal traumatic lesions (intraparenchymal hyper or hypoechoic area or distortion of normal echoic structure).

CEUS: looked for peritoneal fluid and parenchymal lesions, intraparenchymal or subcapsular hematoma, active blush. Injuries appeared as hypoechic perfusion defect or linear lesions. Hematomas are nonenhancing areas. Extravasation of microbubbles outside lacerated organ suggests active bleeding.


Results

256 patients

CT showed 84 (32.8 %) traumatic injuries to liver, spleen, or kidneys and 45 (17.6%) patients with free intraperitoneal fluid


Primary Outcomes


US (without contrast)

  • Positive for traumatic injuries: 50/84 (59.5%)

  • Positive for free fluid 41/45 (91.1%)

  • 1 False positive for organ injury - focal liver lesion on CT

  • 2 false positives for free fluid- young women with small pelvic FF


CEUS

  • Positive for traumatic injuries: 81/84 (96.4%)

  • Positive for free fluid: 43/45 (95.6%) **article stated that this is “same as US” - so unclear if typo or not)

  • 3 False negatives for organ injury - liver lesion, splenic lesion, and kidney contusion (all grade 1)

  • 1 False positive for organ injury - lesion that turned out to be ischemic area of spleen (this wasn’t counted as positive)

CT listed as having 2 false positives for free fluid - unclear from results but this is likely the physiologic free fluid in the pelvis of two young female patients. Appears as though this was counted as false positive for all scans.


For Traumatic Organ Injury

US - Sensitivity 59%, Specificity of 99%

CEUS - Sensitivity 96%, Specificity 99%


For Free Intraabdominal Fluid

US - Sensitivity 91%, Specificity 99%

CEUS - Sensitivity 95%, Specificity 99%

MDCT - Sensitivity 100%, Specificity 99%


Grading

CEUS staged 72/81 recognized traumatic lesions - sensitivity of 88%

9 were under-staged - in five of these cases it missed active bleeding, and in one case missed lesion of urinary tract (other 4 were just understaged by single stage)


Active Bleeding

CEUS found 6/10 with active bleeding - sensitivity of 60%


Limitations

Retrospective

Small population size

Excluded unstable patients or sick patients

16 slice CT - not what many places are using but unlikely to miss most injuries

Do you need the ultrasound machine “contrast-pulse sequencing” to get these results?

Radiologists with specialized training

Did not assess pancreatic or bowel injuries

Unclear who determined the findings - possibly the single radiologist who was performing the scan, meaning no blinding or interrater reliability

Even if US approaches the sensitivity and specificity of CT, does it provide enough information to be able to replace it?


Authors conclude that “patients with negative CEUS may be discharged, monitoring the clinical and laboratory findings, without undergoing CT because only lower grade injuries could be missed”. What do you think?


Take Home Points

1. In mild stable isolated abdominal trauma, contrast enhanced ultrasound was 96% sensitive and 99% specific for organ injuries compared to CT.

2. Contrast enhanced ultrasound has greater sensitivity for intrabdominal free fluid and solid organ injury identification compared to non-contrast enhanced ultrasound.


Our score

3 Probes


Published on 02/13/17 01:00 AM
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