Abstract: Objective To analyze the features and diagnostic value of contrast-enhanced ultrasound in patients with solid liver nodules ≤ 2 cm. Methods 140 patients with solid liver nodules ≤ 2 cm in diameter treated in the hospital were enrolled between June 2018 and December 2020. Conventional ultrasound and contrast-enhanced ultrasound were performed on patients. Results Among 156 lesions, pathological examination showed there were 87 benign lesions, including 28 hemangiomas, 42 regenerative nodules, 5 steatosis, 10 inflammatory necrosis and 2 spiroma. And there were 69 malignant lesions of 20 atypical hyperplasias and 49 small hepatocellular carcinomas (SHCC). Among the hepatocellular carcinomas, there were 23 lesions of high differentiation, 15 moderate differentiation, 6 poor differentiation, 2 clear cell carcinomas, 1 bile duct cystadenocarcinoma, and 2 primary hepatic large cell neuroendocrine carcinomas. With pathological examination as the gold standard, 78 benign cases and 78 malignant cases were diagnosed by conventional ultrasound, and 85 benign cases and 71 malignant cases were diagnosed by contrast-enhanced ultrasound. The Kappa value, correctness, sensitivity, specificity, positive predictive value and negative predictive value were 0.527, 76.3%, 73.6%, 79.7%, 85.0%, and 70.5% of conventional ultrasound diagnosis, and were 0.896, 94.9%, 94.3%, 95.7%, 96.5%, and 93.0% of contrast-enhanced ultrasound. Ultrasound examination results displayed 42 lesions of very low to low echoes, 76 of medium to high echoes and 38 of mixed echoes. Among the 156 lesions, 36 lesions showed rapid enhancement in the arterial phase and fast in and fast out in the portal vein phase, 38 showed fast in but no out until the delayed phase, and 5 showed fast in and slow out until the delayed phase, 27 showed slow in but no out, 1 showed equal enhancement-out in portal vein phase or delayed phase after equal enhancement in the arterial phase, 34 showed equal enhancement in arterial phase, portal vein phase and delayed phase, 16 lesions showed no enhancement in the arterial phase, portal vein phase and delayed phase. The initial increase time of contrast-enhanced ultrasound for benign lesions was (14.5±2.9) s, which was significantly longer than [(11.2±2.8) s, P<0.05] for malignant lesions, and the peak time with (22.9±6.7) s was significantly longer than [(20.6±6.2) s, P<0.05] of malignant lesions, and half time of descent with (169.4±42.6) s was significantly longer than [(66.9±30.4) s, P<0.05] of malignant lesions. Conclusion Contrast-enhanced ultrasound can dynamically monitor the liver tissue microcirculation perfusion in real time, facilitate the observation of the microvascular structure of parenchymal tissues, and help judge the nature of the lesion. Its advantages can better make up for the deficiencies of conventional ultrasound and effectively improve the diagnostic accuracy rate.

Key words: Solid nodules, Contrast-enhanced ultrasound, Diagnosis, Conventional ultrasound, Small hepatocellular carcinoma