Can the multiphasic computed tomography be useful in the clinical management of small renal masses?

BACKGROUND: Small renal masses (SRMs; ≤4 cm) represent a challenging issue. Computed tomography (CT) is widely used for investigating renal tumors even if its ability to differentiate among the different subtypes has not yet been definitively established. PURPOSE: To assess the potential role of the morphological features and angiodynamic behavior on multiphasic CT in the preoperative evaluation of SRMs. MATERIAL AND METHODS: The CT images of 80 patients with SRMs who underwent surgical resection at our institution were retrospectively reviewed. The morphological features, the pattern, and the quantitative analysis of enhancement were assessed for each lesion and were correlated with the histological subtypes. RESULTS: Overall, 81 SRMs were evaluated. Final pathological examination showed 30 (37%) oncocytomas, 22 (27.2%) clear cell renal cell carcinomas (ccRCCs), 16 (19.8%) papillary RCCs (pRCCs), and 13 (16%) chromophobe RCCs (chRCCs). Of the morphological features, only necrosis was significantly associated with ccRCC (P = 0.047). The analysis of enhancement allowed the identification of two groups of lesions, based on arterial behavior: hypervascular (oncocytomas/ccRCC) and hypovascular (chRCC/pRCC) lesions. A significant difference between the two groups in terms of degree of enhancement on CT phases was found (P < 0.05); this was also confirmed by the receiver operating characteristic (ROC) analysis. CONCLUSION: Except for necrosis, the morphological features are not useful in making a correct diagnosis in the case of SRMs. The angiodynamic behavior on multiphasic CT showed high accuracy in differentiating between hypovascular and hypervascular tumors; this differentiation could be useful for deciding on the most appropriate clinical management of SRMs.