In total, the EDCB was observed in 110 of 206 (53.4%) renal tumors. The rates of detection of the EDCB in ccRCC, chromophobe RCC (chRCC), papillary RCC (pRCC), clear cell papillary RCC (ccpRCC), Fp-AML, and oncocytoma, were 66.0% (103 of 156), 18.8% (3 of 16), 0% (0 of 12 ), 50.0% (3 of 6), 0% (0 of 12), and 50.0% (2 of 4), respectively (Figure 2–4). The EDCB was observed in hypervascular tumors, mainly in ccRCC. There was a substantial interobserver agreement for the presence or absence of the EDCB using k statistics (k = 0.767). There was fair interobserver agreement for the presence or absence of the nephrographic and excretory phase high-attenuation rim using k statistics (k = 0.618 and k = 0.514).
The univariate analysis extracted the following significant findings for differentiating ccRCC from Fp-AML: sex, mean tumor size, overflowing beer sign, homogenous enhancement, CT value on unenhanced CT, and EDCB (Table 2 [Figure 6]). The multivariate analysis identified the following independent predictors for ccRCC: male, larger tumor size, lower CT value on unenhanced CT, and presence of the EDCB (Table 3 [Figure 7]). The sensitivity, specificity, PPV, and NPV of the EDCB for differentiating ccRCC from Fp-AML were 66.0%, 100%, 100%, and 18.5%, respectively.
The diagnostic performance of EDCB, nephrographic, and excretory phase high-attenuation rim for pathological peritumoral pseudocapsule in RCC, except for the small number of ccpRCC (n = 6), are summarized in Table 4 (Figure 8). The frequencies of the high-attenuation rim on the nephrographic or excretory phase images in ccRCC were low, 23.3% and 18.6%. It was observed only between the tumor and surrounding fat tissue, especially around the cystic components. The EDCB was associated with pathological pseudocapsules in ccRCC (p = 0.035).