Demonstration of an actively bleeding aneurysm by CT angiography.

We describe a case of an actively bleeding aneurysm demonstrated by CT angiography (CTA). The active hemorrhage was characterized by a nebulous attenuation in the subarachnoid space adjacent to the aneurysm. The measurements (HU) of the hemorrhage were equal to or slightly less than those of the contrast material in the arteries and diminished as one moved further from the aneurysm. As CTA is used more frequently in the diagnosis of cerebral aneurysms, it is important to understand imaging features of this potentially lethal condition.