Incidentally discovered small renal carcinoma: CT and angiography

CT and angiographic features of nine incidentally discovered small renal adenocarcinomas are reviewed. They were all discovered by CT or US during screening procedures or examinations targeting the liver or pancreas. In our institute, they constituted 56 percent of renal adenocarcinomas whose diameters were 4 cm or less. CT without contrast enhancement detected abnormality in seven of the nine, but two were negative or equivocal. Postcontrast CT delineated all tumors as relatively low-density areas, since the normal parenchyma of the kidney showed intense contrast enhancement. We believe that isodense or nearly isodense masses that show relatively low density after contrast are diagnostic of small solid renal tumors. Dynamic study with a bolus injection of contrast medium added information about the vascularity of the tumors. Angiography revealed hypervascularity in only four of the tumors. The rest were avascular or hypovascular. Four tumors that were avascular in the AP arteriographic view were shown to be hypovascular by a tailored oblique view in which adequate obliquity of the angiographic projection was determined by referring to CT, so that the tumors would be seen in profile and would not be superimposed on by normal parenchyma or vertebral shadows.