Introduction and aim of the study - The use of ultrasonography for the detection of parenchymal disorders of the liver is rarely specific. Contrastenhanced ultrasound (CEUS) improves the accuracy of focal liver lesion characterization. Nevertheless, in veterinary medicine, data on liver lesion characterization by CEUS are scant and based on a small number of cases in dogs, and totally missing in cats. Aim of this study is to describe the contrast enhancement pattern of focal liver lesions in dogs and cats.
Materials and methods - 34 dogs and 6 cats with hepatic lesions were considered. Each animal underwent a qualitative contrast-enhanced ultrasound using a contrast agent consisting of sulphur hexafluoride; cytohistology was used as a gold standard for the diagnosis. Sensitivity, specificity, positive and negative predictive values and positive and negative likelihood ratios were determined in order to classify the liver focal lesions examined with Sonovue® as benign or malignant.
Results - CEUS showed that 86.4% of benign lesions had homogeneous enhancement in the portal and late phase compared with the adjacent liver parenchyma; all (100%) malignant lesions showed hypoenhancement in the late phase, while the portal phase ranged from iso- to hypoechoic in primary and metastatic carcinomas.
Discussion - The results of our study confirm the usefulness of CEUS in differentiating benign from malignant lesions. Nevertheless, three cases of benign lesions with atypical behaviour were detected. The main differences in terms of vascular behaviour were registered in the late phase, with hypoenhancement in malignant lesions in both the dog and the cat. In four cases (10%), hypoenhancement was detected in the advanced late phase, suggesting that observation must be prolonged for at least 2 minutes in order to avoid possible false negatives. Pathognomonic patterns capable of characterizing specific lesions were not recognized. In our experience, Sonovue® showed a high sensitivity and specificity in the differentiation of benign or malignant liver focal lesions. CEUS, a non-invasive and relatively cheap technique, could have an important role in the diagnostic approach to characterize hepatic lesions in dogs and cats, particularly when more complete exams (i.e. CT) and/or biopsy are not available.