Solid Organ Injuries: Contrast-Enhanced US versus CT

The objective of a recent study was to compare the sensitivity and specificity of routine ultrasound with that of contrast-enhanced ultrasound to depict solid organ injuries in children with blunt abdominal trauma using contrast-enhanced CT scanning as a Reference standard.

The study has concluded that as a noninvasive modality, contrast-enhanced ultrasound approaches contrast-enhanced CT in diagnostic performance in depicting solid organ injuries in children.

Methodology
Over a three-year period, 27 hemodynamically stable patients with moderate or severe injuries were initially evaluated with routine ultrasound and subsequently by contrast-enhanced ultrasound and CT. Each of the three imaging techniques was performed by three respective individuals, who later interpreted the results while blinded to the results of the other examinations.

Routine ultrasound was performed to detect free fluid, consisting of prolonged scanning in all four quadrants with concentrations in the epigastrium, pericardial space, and right and left colic gutters. Contrast-enhanced ultrasound was performed immediately after using a second-generation blood pool contrast agent. The agent was injected as a bolus with a 22-gauge catheter.

The complete contrast-enhanced exam lasted no more than six minutes. Un-enhanced and contrast-enhanced CT examinations were performed immediately after ultrasound. Subsequent statistical analysis was employed.

Results of the Study
44% of the 27 patients had 14 injuries that were demonstrated on contrast-enhanced CT images. Routine ultrasound was positive in 10 patients, rendering routine ultrasound 57.1% sensitive and 86.7% specific.

On the other hand, contrast-enhanced ultrasound depicted 13 of 14 lesions, with only a right adrenal gland contusion missed. All 15 patients who had no organ injuries depicted on CT also had normal contrast-enhanced ultrasound.

On contrast-enhanced ultrasound images, organ injuries appeared as strongly hypoechoic areas adjacent to hyperechoic parenchyma. Microbubbles within the lesion indicated active bleeding. The sensitivity and specificity of contrast-enhanced ultrasound was calculated to be 92.9% and 100%, respectively.

Reviewer’s Comments
This is a very interesting article showing that, when used in experienced hands, contrast-enhanced ultrasound accuracy approaches contrast-enhanced CT scanning when depicting solid organ injuries in children.

The authors do not comment on the importance of excluding other types of injuries, for which ultrasound may not be useful, such as osseous or vascular injuries. In practical terms, it may not be worth performing a contrast-enhanced ultrasound in a child only to delay the inevitable CT, which will most likely be used to complete the injury profile.

Author: Basil Hubbi, MD

Reference
Valentino M, Serra C, et al. Blunt Abdominal Trauma: Diagnostic Performance of Contrast-Enhanced US in Children–Initial Experience.
Radiology; 2008; 246 (March): 903-909.