[Differentiation of subtypes of renal cell carcinoma by double-phase helical computed tomography]

To evaluate the imaging features of different subtypes of renal cell carcinoma (RCC) by double-phase helical computed tomography (CT) and to enhance its pre-operative diagnosis level.

A total of 460 RCC were reviewed retrospectively. Tumor size, enhancement degree, enhancement drop between corticomedullary (CMP), nephrographic (NP), enhancement pattern, and tumor density (homogeneity, degeneration or necrosis, calcification) were observed respectively. The clear cell, chromophobe and papillary types were analyzed for statistical analysis.

They had difference in enhancement pattern and tumor density of clear cell, chromophobe (P < 0.05) and papillary types (P < 0.05). There were differences in enhancement degree, enhancement drop and combine degeneration or necrosis in all subtypes of RCC (P < 0.05). The clear cell type was of hypervascular tumor and showed a stronger enhancement (80.9%) than other types. The enhancement drop was also higher than other types and 57.9% of it was ≥ 30 HU. As for ≥ 30 HU, the clear cell type was diagnosed with a 57.9% sensitivity and a 91.9% specificity. Clear cell type tended to appear as peripheral and heterogeneous enhancement (66.3%, 94.6%); it was likely heterogeneous in density (91.6%) with frequent degeneration or necrosis (60.5%). The chromophobe type was of moderate vascular tumor and it exhibited middle-level enhancement (77.1%). The enhancement drop was low (< 30 HU, 80.0%). As for 0-30 HU, the chromophobe type was diagnosed with an 80.0% sensitivity and a 66.1% specificity. Its pattern ended to appear as homogeneous enhancement (65.7%); Homogeneous density, degeneration and necrosis were characteristic signs of chromophobe type. The papillary type was of hypovascular tumor and it exhibited slight or no enhancement (70.4%). The enhancement drop was low (< 30 HU, 92.6%) and the gradual enhancement (63.0%) was characteristic of this type. As for 0 Hu, the papillary type was diagnosed with a 63.0% sensitivity and a 91.8% specificity. It tended to appear as homogeneous density (63.0%). The unclassified type tended to appear as peripheral (9/12 cases) and stronger enhancement (7/12 cases) and heterogeneous density with degeneration or necrosis (9/12 cases). The multilocular cystic RCC appeared as complex cyst. And cystic wall enhancement was an important diagnostic point of cystic RCC.

Double-phase helical CT plays an important role in the pre-operative differentiation of subtypes of RCC. Each type of RCC has its own features. A clinician may reach a correct pre-operative diagnosis.