Value of contrast-enhanced ultrasound in diagnosis of atypical renal space occupying lesions

Objective To evaluate the diagnostic value of contrast-enhanced ultrasound(CEUS) in renal atypical space occupying lesions. Methods The images of conventional ultrasound and CEUS in 44 patients with 47 renal atypical space occupying lesions from May 2015 to June 2019 were retrospectively analyzed, including 26 males and 18 females. The mean age of patients was(55.9±13.7)years old, ranged from 27 to 79 years old. The mean size of the lesions in conventional ultrasound was (2.5±1.3)cm, ranged from 1.0 to 6.0 cm. The location, size, echo, boundary and color flew signals of renal lesions were observed by conventional ultrasound.The degree and the pattern of enhancement, presence or absence of a clear capsule sign were analyzed by CEUS. The ultrasound diagnosis results were compared with the pathological or clinical diagnosis. Results Of the 47 lesions, 15 were malignant and 32 were benign. 19 lesions were diagnosed by operation pathology, including 13 renal cell carcinomas, 2 renal lymphomas, 3 renal cysts and 1 inflammatory granuloma; the other 28 benign tumors or pseudotumors were diagnosed by enhanced CT or MRI, and were followed up for more than 1 year, including 5 angiomyolipomas, 15 cysts, 3 renal junction cortex defects, 2 renal column hypertrophies, 1 local non-atrophic renal parenchyma, 1 hump kidney and 1 scar. Most of the renal cell carcinomas were hypoechoic (8/13), "fast wash-in and fast wash-out " (9/13), heterogeneous hypoenhancement (6/13), 9 with pseudocapsule and 6 with necrosis. 2 renal lymphomas were hypoechoic, "fast wash-in and fast wash-out" , 1 isoenhancement and 1 hypoenhancement. The angiomyolipomas were hyperechoic, "slow wash-in and slow wash-out" (4/5), 2 hypoenhancement, 2 hyperenhancement and 1 isoenhancement. Most renal cysts were anechoic(16/18). There was no enhancement in simple renal cysts. The wall or septum of complex renal cysts was thin and homogeneous enhanced, showing "slow wash-in and slow wash-out" with isoenhancement or hypoenhancement. Inflammatory granuloma was cystic-solid. The solid part was hypoenhancement. Renal column hypertrophy, hump kidney and local non-atrophic renal parenchyma were hypoechoic, showing the same enhancement pattern as renal parenchyma by CEUS. The junctional parenchyma defect and renal scar were hyperechoic, showing no enhancement. The sensitivity, specificity, accuracy and the area under the ROC curve of conventional ultrasound and CEUS in the diagnosis of benign and malignant lesions were 86.7%, 87.5%, 87.2%, 0.871 and 100.0%, 96.9%, 97.9%, 0.984.There were significant differences in the diagnosis of renal atypical space occupying lesions between two methods (P=0.03). Conclusions CEUS was better than conventional ultrasound in the diagnosis of renal atypical space occupying lesions. CEUS had advantages in the differential diagnosis of benign and malignant tumors, benign lesions and anatomical variants mimicking a renal tumor. Key words: Kidney neoplasms; Contrast-enhanced ultrasound; Diagnosis