Table 1.

Summary of key findings of contrast-enhanced ultrasound studies.

Study (Year)	Study Type	Type of Renal Mass	Number of Patients (Tumors)	Imaging Type	Key Findings
Furrer et al. (2020)	Systematic review	Solid and cystic renal masses	1290 (1342)	CEUS vs. CECT/CEMRI	CEUS performs at least as well or better than CECT and CEMR in the qualitative diagnosis of benign vs. malignant renal masses.
Yong et al. (2016)	Retrospective cohort study	Indeterminate renal masses in patients with renal impairment	63 (74)	CEUS	CEUS has a high diagnostic performance for the prediction of benignity of renal masses in patients with renal impairment with sensitivity and NPV approaching 100%.
Zhou et al. (2011)	Retrospective cohort study	Solid renal masses with histopathology available or follow-up with MRI	51 (51)	CEUS	CEUS results in good diagnostic confidence for the diagnosis of RCC with a sensitivity of 86% and a specificity of 93%.
Rübenthaler et al. (2018)	Retrospective cohort study	Indeterminate renal masses with histopathology available	255 (255)	CEUS	CEUS resulted in a sensitivity of 99.1% and a sensitivity of 80.5% for the differentiation of being benign vs. malignant.
Lerchbaumer et al. (2020)	Retrospective cohort study	Cystic renal masses	173 (173)	CEUS vs. CECT/CEMRI	CEUS outperforms CECT and CEMRI in the characterization of fine septal and nodular enhancements in cystic renal masses, often leading to an upgrade in Bosniak classification.
Sanz et al. (2016)	Prospective cohort study	Bosniak II–IV cystic renal masses	67 (67)	CEUS vs. CECT	CEUS has a good agreement with CECT regarding the Bosniak classification. Sensitivity and NPV were 100% for the differentiation of benign vs. malignant cystic renal masses.
Ragel et al. (2016)	Prospective cohort study	Cystic renal masses	46 (51)	CEUS vs. CECT	CEUS upstaged cystic renal masses in 31% of cases compared with assessment using CECT.
Defortescu et al. (2017)	Prospective cohort study	Bosniak IIF and III cystic renal masses	47 (47)	CEUS vs. CECT	CEUS outperformed CECT for the differentiation of Bosniak IIF and III cystic renal masses into benign or malignant with a sensitivity of 100%, a specificity of 97% and an NPV of 100%.
Rübenthaler et al. (2016)	Retrospective cohort study	Indeterminate renal masses	36 (36)	CEUS vs. CEMRI	CEUS is useful for the differentiation of benign vs. malignant renal masses, with a sensitivity, specificity and NPV comparable to CEMRI.
Wei et al. (2017)	Retrospective cohort study	Small (<4 cm) renal masses	118 (118)	CEUS vs. CECT	Both CEUS and CECT are effective for the differentiation of benign vs. malignant small renal masses, with a sensitivity for CEUS of 93.5%, a specificity of 68% and an NPV of 73.9%.
Zhang et al. (2019)	Systematic review	Solid and cystic renal masses	NR (2260)	CEUS vs. CECT	CEUS has a higher sensitivity and a comparable specificity for the detection of renal cancer compared with CECT (94% vs. 85% and 77% vs. 75%, respectively).
Zhou et al. (2018)	Systematic review	Cystic renal masses	NR (1142)	CEUS vs. CEMRI	Both CEUS and CEMRI have good diagnostic performance for the differentiation of cystic renal masses in benign vs. malignant renal masses. CEUS has a higher sensitivity, but lower specificity for this diagnosis compared with CEMRI (95% vs. 92% and 84% vs. 91%, respectively).

Studies are listed in the order of mention in the article’s main text. CEUS—contrast-enhanced ultrasound, CECT—contrast-enhanced computed tomography, CEMRI—contrast-enhanced magnetic resonance imaging, NPV—negative predictive value, RCC—renal cell carcinoma, NR—not reported.