A sac formed by the localized dilatation of the wall of an artery, vein or the heart.
- aortic a. — see aortic aneurysm.
- arteriovenous a. — an abnormal communication between an artery and a vein in which the blood flows directly into a neighboring vein or is carried into the vein by a connecting sac.
- atherosclerotic a. — one arising as a result of weakening of the tunica media in severe atherosclerosis.
- bacterial a. — an infected aneurysm caused by bacteria.
- berry a. — a small saccular aneurysm of a cerebral artery, usually at the junction of vessels in the circle of Willis; such aneurysms frequently rupture, causing subarachnoid hemorrhage. Called also brain aneurysm.
- cardiac a. — thinning and dilatation of a portion of the wall of the left ventricle, usually a consequence of myocardial infarction.
- cirsoid a. — dilatation and tortuous lengthening of part of an artery.
- compound a. — one in which some of the layers of the wall of the vessel are ruptured and some merely dilated. Called also mixed aneurysm.
- congenital a. — observed sporadically in the aorta and pulmonary artery.
- dissecting a. — one resulting from hemorrhage that causes lengthwise splitting of the arterial wall, producing a tear in the inner wall (intima) and establishing communication with the lumen of the vessel; it usually affects the thoracic aorta. Seen most commonly in horses and caused by larvae of Strongylus vulgaris. See strongylosis. A specific disease of turkeys.
- fusiform a. — a spindle-shaped aneurysm.
- infected a. — one produced by growth of microorganisms (bacteria or fungi) in the vessel wall, or infection arising within a pre-existing arteriosclerotic aneurysm.
- inherited aortic a. — causes a high mortality rate in the affected cattle breed. The defect is in the abdominal aorta.
- lung a. — may result from the lodgement of pulmonary emboli; rupture and pulmonary hemorrhage are potential sequelae.
- mixed a. — compound aneurysm.
- mycotic a. — an infected aneurysm caused by fungi.
- pseudoaneurysm — false aneurysm.
- racemose a. — cirsoid aneurysm.
- sacculated a. — a saclike aneurysm.
- varicose a. — one formed by rupture of an aneurysm into a vein. See also aneurysmal varix.
- venous a. — see venous dilatation.
- verminous a. — see strongylosis.
