The role of strain elastography in the evaluation of caninehypoechoic splenic lesions

In human medicine elastosonography is helpful in differentiating benign from malignant lesions in several organs.The elastosonography has been described in veterinary medicine. Some authors found that elastosonography was not helpful in differentiating canine splenic nodules. This study aims to assess the repeatability and reproducibility of elastosonography in the evaluation of splenic nodules and to verify if it can differentiate benign from malignant splenic lesions in dogs. Twenty-two dogs presenting a single splenic hypoechoic lesion less than 4 cm width, underwent ultrasonographic evaluation (two-dimensional ultrasound and strain elastosonography with a 7,5-13 MHz linear transducer). The Strain Ratio (SR or rather z2/z1; where z1 represented the entire lesion and z2 a same size portion of normal splenic parenchyma at the same depth) and Hardness Value (HV; percentage of the lesion having > 50% of tissue classified as hard) were calculated for all the lesions. The repeatability and the reproducibility of this method were assessed calculating the Coefficient of Variability (CV) and the K of Cohen respectively. The analysis of the variance (ANOVA) and the Fisher exact test were used to verify the differences between the SR values and HV of benign versus malignant lesions. The cut off values for the Fisher test were arbitrarily set at 1,5 for the SR and at 70 % for HV; the Sensibility (Se) and Specificity (Sp) were also calculated. The Odds ratio was also calculated considering malignancy as bad outcome; lesions having a SR > 1,5 and lesions having an HV > 70% were considered in the exposed group. Splenic nodules were diagnosed with cytology or histopathology as: extramedullary hematopoiesis (2), nodular iperplasia (13), hemangiosarcoma (5) and round cell neoplasia (2). The SR and HV of benign lesions were statistically different from those of malignant lesions (p<0,05). Malignant lesions tended to have a SR >1,5 (p=0,001; Se 71%, Sp 99,9%) and an HV > 70% (p=0,005; Se 100%, Sp 67%). The correlation between SR >1,5 and malignancy was statistically significant (OR, 63,8; 95% CI, 2,6238-1551,3391, p=0,01) as the one between HV >70% and malignancy (OR, 28,6; CI 95% 1,3657-600,4393, p=0,03). This technique was repeatable and reproducible (CV 0,08 ± 0,03 and K=1 for the SR; CV 0,08 ± 0,05 and K=0,66 for the HV). Elastosonography can differentiate malignant from benign canine hypoechoic splenic lesions less than 4 cm width.