Helical CT with sagittal and coronal reconstructions: accuracy for detection of diaphragmatic injury

OBJECTIVE. The objectives of our study were to determine the accuracy of single-detector helical CT (including coronal and sagittal reconstructions) for the diagnosis of traumatic diaphrag- matic injury, establish measurements for the thickness of the normal diaphragmatic crus, and de- scribe an additional sign of diaphragmatic injury: active arterial extravasation of contrast material at the level of the diaphragm. MATERIALS AND METHODS. The CT scans of 25 patients with surgically proven dia- phragmatic injury and 22 patients with surgically confirmed uninjured diaphragms were blindly re- viewed by five thoracic radiologists. Sagittal and coronal reconstructions were performed for 20 of the 25 patients with a proven diaphragmatic injury and for all the patients without a diaphragmatic in- jury. Scans were evaluated for findings suggestive of diaphragmatic injury and for associated injuries. Reviewers scored the usefulness of the reconstructed images for establishing the final diagnosis. Measurements of the right and left crura were performed to establish a threshold measurement that would enable radiologists to discriminate between a normal diaphragm and an injured diaphragm. RESULTS. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of helical CT were 84%, 77%, 81%, 81%, and 83%, respectively. Scans showing active arterial extravasation of contrast material enabled reviewers to correctly identify diaphrag- matic injury in two patients. Reconstructed images confirmed the correct diagnosis in three pa- tients but supported an incorrect diagnosis in two. The mean thickness of the diaphragmatic crura (right and left) was not significantly greater in patients with an injured diaphragm than in those with an uninjured diaphragm. CONCLUSION. Helical CT shows good sensitivity, specificity, and accuracy for the diag- nosis of diaphragmatic injury. Coronal and sagittal reconstructions are of limited use in establish- ing or refuting this diagnosis. Active arterial extravasation of contrast material near the diaphragm should raise suspicion for injury. Crus measurements cannot be used to reliably distinguish be- tween injured and uninjured diaphragms.