QUANTITATIVE ELASTOGRAPHY OF RECTAL LESIONS: THE VALUE OF SHEAR WAVE ELASTOGRAPHY IN IDENTIFYING BENIGN AND MALIGNANT RECTAL LESIONS

We evaluate the value of shear wave elastography (SWE) in diagnosing benign and malignant rectal lesions. A total of 96 lesions were reviewed in this study; endorectal ultrasound (ERUS) and SWE examinations were performed before surgery in all cases. Elasticity parameters including mean elastographic index (E-mean), maximum elastographic index (E-max) and minimum elastographic index (E-min) were analyzed. Correlations between elastographic parameters and histopathological results were studied. Inter-observer and intra-observer agreement was analyzed. Of the 96 rectal lesions, 72 were malignant and 24 were benign. Compared with ERUS, ERUS + SWE had higher sensitivity (93.0% vs. 88.9%), specificity (83.3% vs. 79.2%), positive predictive value (94.4% vs. 92.7%), negative predictive value (80.0% vs. 70.4%) and overall accuracy (90.6% vs. 86.4%). In receiver operating characteristic curve analysis, E-mean and E-max had larger areas under the curve: 0.92 and 0.91, respectively. The optimal cutoff value was 61.3 kPa for E-mean (sensitivity = 88.9%, specificity = 87.5%) and 63.4 kPa for E-max (sensitivity = 94.4%, specificity = 83.3%). We obtained kappa values of 0.83 (95% confidence interval [CI]: 0.72-0.95) for ERUS and 0.90 (95% CI: 0.81-0.99) for ERUS + SWE of differential diagnosis in two observers. The intra-class correlation coefficients for intra-observer variability of stiffness (E-mean) in malignant lesions, benign lesions, surrounding normal rectal wall in malignant lesions and surrounding normal rectal wall in benign lesions were 0.91 (95% CI: 0.86-0.94), 0.94 (95% CI: 0.88-0.97), 0.92 (95% CI: 0.88-0.95) and 0.89 (95% CI: 0.77-0.95), respectively. SWE is a promising tool that yields valuable quantitative data additional to that provided by ERUS examination in rectal lesions. The cutoff value 61.3 kPa for E-mean may serve as a complementary tool in diagnosis of rectal lesions. (C) 2018 World Federation for Ultrasound in Medicine & Biology. All rights reserved.