Differentiating Transudative From Exudative Ascites Using Quantitative B-Mode Gray-Scale Ultrasound Histogram

OBJECTIVE. The purpose of this article is to differentiate exudative from transudative ascites using B-mode gray-scale ultrasound histogram analysis. SUBJECTS AND METHODS. Sixty-two consecutive patients with ascites were prospectively studied from June 2014 through June 2015. All underwent ultrasound (US) and paracentesis in the radiology department. Five patients were excluded (three with hemorrhage and two with peritoneal carcinomatosis). The remaining 57 patients were divided into those with exudative and transudative ascites according to results of paracentesis. Electronically recorded US images were transferred to a workstation, and gray-scale histograms were generated. The ascites-to-rectus abdominis muscle echogenicity ratio (ARAER) was obtained from ascites adjacent to the rectus abdominis muscle. ROC curves were used to evaluate the sensitivity and specificity of this method in differentiating exudative from transudative ascites. RESULTS. ARAERs for exudative ascites were significantly higher than those for transudative ascites (p < 0.001). ROC was done to evaluate ARAERs for exudative ascites. The best cutoff value for ARAER histogram was 0.002. The sensitivity and specificity of ARAER were 87.5% and 79.2% (AUC = 0.843), respectively. CONCLUSION. ARAER is an easily applicable noninvasive quantitative sonographic method with high sensitivity and specificity in differentiating exudative from transudative ascites.