Sonographic detection of acute parenchymal injury in an experimental porcine model of renal hemorrhage: Gray-scale imaging using a sonographic contrast agent

OBJECTIVE. The purpose of this study was to determine the usefulness of con trast-enhanced sonography in the detection of acute parenchymal injury. SUBJECTS AND METHODS. In a model of acute renal injury in pigs, four separa te renal parenchymal bleeds were created by puncturing an interlobar artery of the upper and lower poles of the kidneys. B-mode gray-scale scans of th e kidneys before and after injury, and after the administration of IV and i ntraarterial (IA) contrast agents were recorded on videotape for 5 min for each condition (baseline, after injury, after IV contrast administration, a nd after IA contrast administration). For each condition and injury, select ed frames were analyzed with regions of interest of the normal renal parenc hyma, the area of injury, and the perinephric space. Randomized videotape c lips from each of the experimental conditions were rated by three sonologis ts as to the presence or absence of increased intrarenal parenchymal echoge nicity, perinephric echogenicity, and confidence as to whether renal injury was present. RESULTS. Areas of renal injury were isoechoic with normal parenchyma on une nhanced scans. After both IV and IA contrast material injection, areas of i njury were visible as areas of increased echogenicity. Contrast increased f rom 0.2 on unenhanced images to 4.0 and 4.5, respectively, after:IV and IA administration of the new contrast agent. The three observers' ability to d iagnose renal injury increased from 0.61, 0.64, and 0.54 to 0.71, 0.70, and 0.74 after IV injection and to 0.93, 0.92, and 0.97 after IA injection as indicated by the area under the curve in the receiver operating characteris tic analysis. CONCLUSION. Transabdominal contrast-enhanced gray-scale sonography can reve al the area of acute renal hemorrhage. This procedure may be applicable in patients when sonographic contrast agents, imaging procedures, and modes of contrast administration are optimized for clinical use in trauma.