[Changes in renal tumor contrasting in multiphasic SCT]

Changes in renal tumor contrast and renal parenchyma-tumor density gradient were determined at multiphasic spiral computed tomography (SCT). A hundred and seven patients with renal tumors underwent SCT in the native phase and after bolus intravenous contrasting in the corticomedullary, nephrographic, and early excretory phases of the study. According to the level of contrast-enhancement in the corticomedullary phase, the neoplasms were divided into three groups: intensive, moderate, and low contrasting. Intensively and moderately contrast-enhancement tumors showed the maximal contrast in the corticomedullary phase of the study with a significant reduction in density values in the nephrographic and early excretory phases. Lowly contrast-enhancement tumors generally demonstrated a slow gradual increase in their contrast from the native phase to the corticomedullary and nephrographic ones with their minimum contrast changes between the nephrographic and early excretory phases. In this group of patients, the difference was frequently insignificant between the neoplasmic density values in the native and corticomedullary phases in this group of patients, so it is expedient to use a combination of native and nephrographic or native and early excretory phases to make a differential diagnosis of hypovascular tumors and renal cysts. The maximum intact renal parenchyma-tumor density gradient was detectable in the nephrographic phase therefore this study phase is of the greatest information value in detecting renal tumors.