US Abdomen with IV Contrast CEUS using microbubble agents is emerging as a useful way to characterize previously indeterminate renal lesions [16-18]. In a study of 1,018 indeterminate renal lesions, CEUS had a per patient sensitivity of 100% (126 of 126 patients), specificity of 95% (132 of 139 patients), positive predictive value of 94.7% (126 of 133 patients), and negative predictive value of 100% (132 of 132 patients) for classifying benign versus malignant renal masses [16]. In that study, any echogenic masses with enhancement equal to or greater than normal renal cortex and wash-out, and any masses with blood flow, were considered malignant. In another study, CEUS successfully classified 95.7% (90 of 94) previously indeterminate lesions and has an accuracy of 90.2% (37 of 41 lesions) when compared with the reference standard, including histopathology and follow-up [18]. In the subgroup analysis, CEUS was definitive for 94.4% (17 of 18) of cases referred because of equivocal enhancement at CT [18]. In that same study, CEUS was able to classify lesions in 100% (10 of 10) of the cases in which the lesions were indeterminate on prior MRI [18]. Another study of CEUS in 83 CT indeterminate renal masses reported that the accuracy of characterization by CEUS was 95.2% compared with 42.2% using unenhanced US [17]. Studies have shown CEUS to be more sensitive than contrast-enhanced CT in characterizing cystic renal masses [19,65]. In a study of 31 cystic renal masses evaluated by both CT and CEUS using the Bosniak classification, 26% of the lesions were upgraded by CEUS [19]. In a prospective CEUS study of 94 solid renal lesions excluding lipid- rich AML, hypovascularity of small solid renal masses relative to the cortex in the arterial phase has 100% specificity for detecting malignancy, especially for detecting papillary RCC [66]. Quantitative analysis of CEUS has also been reported to be useful to stratify RCC and benign renal tumors [67,68]. Variant 2: Indeterminate renal mass.
Indeterminate Renal Mass. US Abdomen with IV Contrast CEUS using microbubble agents is emerging as a useful way to characterize previously indeterminate renal lesions [16-18]. In a study of 1,018 indeterminate renal lesions, CEUS had a per patient sensitivity of 100% (126 of 126 patients), specificity of 95% (132 of 139 patients), positive predictive value of 94.7% (126 of 133 patients), and negative predictive value of 100% (132 of 132 patients) for classifying benign versus malignant renal masses [16]. In that study, any echogenic masses with enhancement equal to or greater than normal renal cortex and wash-out, and any masses with blood flow, were considered malignant. In another study, CEUS successfully classified 95.7% (90 of 94) previously indeterminate lesions and has an accuracy of 90.2% (37 of 41 lesions) when compared with the reference standard, including histopathology and follow-up [18]. In the subgroup analysis, CEUS was definitive for 94.4% (17 of 18) of cases referred because of equivocal enhancement at CT [18]. In that same study, CEUS was able to classify lesions in 100% (10 of 10) of the cases in which the lesions were indeterminate on prior MRI [18]. Another study of CEUS in 83 CT indeterminate renal masses reported that the accuracy of characterization by CEUS was 95.2% compared with 42.2% using unenhanced US [17]. Studies have shown CEUS to be more sensitive than contrast-enhanced CT in characterizing cystic renal masses [19,65]. In a study of 31 cystic renal masses evaluated by both CT and CEUS using the Bosniak classification, 26% of the lesions were upgraded by CEUS [19]. In a prospective CEUS study of 94 solid renal lesions excluding lipid- rich AML, hypovascularity of small solid renal masses relative to the cortex in the arterial phase has 100% specificity for detecting malignancy, especially for detecting papillary RCC [66]. Quantitative analysis of CEUS has also been reported to be useful to stratify RCC and benign renal tumors [67,68]. Variant 2: Indeterminate renal mass.