Pituitary microadenomas: early enhancement with dynamic CT--implications of arterial blood supply and potential importance.

In a search for early contrast medium enhancement, which can indicate the presence of direct arterial supply, a retrospective review of dynamic computed tomographic (CT) scans was performed in 260 patients with a pituitary microadenoma smaller than 10 mm in diameter. Fifty patients underwent examination with dynamic CT for nonendocrinologic disease as a control group to establish the normal pattern of pituitary gland enhancement. One hundred seventy microadenomas (65.4%) displayed the usual dynamic CT pattern (ie, they did not show early enhancement before that of the portal system of the pituitary gland: those pituitary microadenomas appeared less enhanced than the normal pituitary gland during the entire examination). On the other hand, in 90 microadenomas (34.6%), early partial or complete enhancement was seen within the microadenoma before the normal portal enhancement of the gland. Therefore, analysis with dynamic CT yields two groups of pituitary microadenomas separable on the basis of blood supply: those with portal blood supply only and those with partial or predominantly direct arterial blood supply; in theory, the second group avoids hypothalamic control.