CT of melanoma liver metastases: is the examination without contrast media superfluous?

The current method of evaluating hypervascular liver metastases with CT includes both contrast enhanced and unenhanced studies. The necessity of performing both examinations for the detection of liver metastases in the workup of malignant melanoma has not been specifically addressed. This study evaluates potential additional information derived from an unenhanced examination of the liver. We studied 55 patients with malignant melanoma who had both contrast enhanced and unenhanced CT examinations performed during the workup and staging of their disease. Sixteen patients had 89 measurable liver lesions seen on enhanced CT. Three patients had liver lesions that were too numerous to accurately measure. Unenhanced CT demonstrated only 62% of the measurable lesions. All liver lesions seen on the unenhanced images were identified on the enhanced studies. Only one metastasis was found to be comparatively smaller on the enhanced examinations. The unenhanced examinations detected no additional lesions. It is reasonable to perform only an enhanced examination during the workup and staging of malignant melanoma liver metastases.