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A lesion characterised by a weakness in the wall of an artery, vein, or cardiac ventricle, resulting in blood-filled dilation or ballooning, or splitting of the wall.
Clinical findings
Pulsating mass, bruit (aneurysmal bruit over the swelling), ± symptoms from pressure on contiguous parts.

Risk factors
Atherosclerosis, hypertension.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


, aneurism (an'yu-rizm) [Gr. aneurysma, a widening]
Localized abnormal dilatation of a blood vessel, usually an artery, due to a congenital defect or weakness in the wall of the vessel. As aneurysms dilate, they become more and more vulnerable to rupture. aneurysmal (an?yu-riz'mal), adjective


As people age, the combined effects of high blood pressure and atherosclerotic weakening of arteries produce most aneurysms in the aorta. Congenital malformations of arteries in the circle of Willis are relatively common causes of aneurysms in the brain. Aneurysms in the chest or peripheral arteries are sometimes caused by blunt trauma or by bacterial or mycotic infection.

abdominal aortic aneurysm

Abbreviation: AAA
A localized dilatation (saccular, fusiform, or dissecting) of the wall of the abdominal aorta. It is generally found to involve the renal arteries and frequently the iliac arteries. Occasionally the dilatation can extend upward through the diaphragm.

The patient is usually asymptomatic, and diagnosis is made accidentally during a routine physical examination or abdominal x-ray or during screening of the elderly hypertensive male. Serial ultrasounds confirm the diagnosis and determine the size, shape, and location of the aneurysm. Small, asymptomatic aneurysms may be followed over time, rather than repaired (see below). Computed tomography, magnetic resonance imaging, or aortography may assist in confirming the diagnosis and the condition of proximal and distal vessels.


Symptoms, when present, include generalized abdominal pain, low back pain unaffected by movement, and sensations of gastric or abdominal fullness. Sudden severe lumbar or abdominal pain radiating to the flank and groin, esp. if associated with tachycardia and hypotension, may indicate enlargement or imminent rupture. Signs can include a pulsating mass in the periumbilical area and a systolic bruit over the aorta.


Untreated abdominal aortic aneurysms gradually enlarge and in some instances rupture. The likelihood of rupture increases for aneurysms that are larger than 5.5 cm. Surgical repair is recommended for all aneurysms larger than 6 cm. If an aneurysm is tender and known to be enlarging rapidly (no matter what its size), surgery is strongly recommended. Surgical therapy consists of replacing the aneurysmal segment with a synthetic fabric (Dacron) graft. Immediate surgery is indicated for a ruptured aortic abdominal aneurysm. An alternative treatment to traditional laparotomy is to insert a bypass graft percutaneously into the aorta.

Patient care

In acute dissection of an abdominal aortic aneurysm, oxygenation, blood pressure and cardiac rhythm are closely monitored, and a pulmonary artery line may be inserted to monitor hemodynamics. The patient is observed for signs of rupture, which may be fatal. He will require an intravenous line via a large-bore catheter, a urinary catheter, and an arterial line and pulmonary artery catheter to monitor fluid and hemodynamic balance. Additionally, cardiac monitor electrodes will be placed, and a nasogastric tube inserted.

Prescribed medications are administered to manage contributory factors such as hypertension and hypercholesterolemia; a beta-adrenergic blocking agent may be prescribed to reduce the risk of expansion and rupture. The patient is instructed in their use and taught about adverse effects that should be reported. In acute aortic rupture, admission to the intensive care unit is arranged, a blood sample is obtained for typing and cross-matching, and a large-bore (14G) venous catheter is inserted to facilitate blood replacement. The patient is prepared for and informed about elective surgery if indicated or emergency surgery if rupture occurs. The patient will require an intravenous line via a large-bore catheter, a urinary catheter, and an arterial line and pulmonary artery catheter to monitor fluid and hemodynamic balance. Additionally, cardiac monitor electrodes will be placed, and a nasogastric tube inserted. During surgery the patient will be intubated and mechanically ventilated, and such therapies will most likely still be in place postoperatively in the ICU.

Desired outcomes include the patient's ability to express anxiety, use support systems, and perform stress reduction techniques that assist with coping; demonstrated abatement of physical signs of anxiety; avoidance of activities that increase the risk of rupture; understanding of and cooperation with the prescribed treatment regimen; ability to identify indications of rupture and to institute emergency measures; maintenance of normal fluid and blood volume in acute situations; and recovery from elective or emergency surgery with no complications. Generally post-operative patients are assisted to ambulate by the second day after surgery. Pain management and psychological support are extremely important during the acute postoperative period.


Because of the relatively high incidence of AAA in men over age 60 (esp. smokers or men with intermittent claudication) and patients with myesthenia gravis, screening for AAA is recommended for these people.

Enlarge picture

aortic aneurysm

An aneurysm affecting any part of the aorta from the aortic valve to the iliac arteries. The dilated artery is usually asymptomatic, detected as an incidental finding during imaging. See: illustration

arteriovenous aneurysm

An aneurysm of congenital or traumatic origin in which an artery and vein become connected. Symptoms may include pain, expansive pulsation, and bruits or, occasionally, high-output heart failure.

atherosclerotic aneurysm

Aneurysm due to degeneration or weakening of the arterial wall caused by atherosclerosis.

Bérard's aneurysm

See: Bérard's aneurysm

berry aneurysm

A small saccular congenital aneurysm of a cerebral vessel. It communicates with the vessel by a small opening. Rupture of this type of aneurysm may cause subarachnoid hemorrhage, a devastating form of stroke.

cerebral aneurysm

Aneurysm of a blood vessel in the brain.

Charcot-Bouchard aneurysm

See: Charcot-Bouchard aneurysm

cirsoid aneurysm

A dilatation of a network of vessels commonly occurring on the scalp. The mass may form a pulsating subcutaneous tumor.
Synonym: racemose aneurysm

compound aneurysm

Aneurysm in which some of the layers of the vessel are ruptured and others dilated.

dissecting aneurysm

Aneurysm in which the blood makes its way between the layers of a blood vessel wall, separating them; a result of necrosis of the medial portion of the arterial wall.
See: aortic aneurysm for illus.

fusiform aneurysm

Aneurysm in which all the walls of a blood vessel dilate more or less equally, creating a tubular swelling.
See: aortic aneurysm for illus.

mycotic aneurysm

Aneurysm due to bacterial infection.

racemose aneurysm

Cirsoid aneurysm.

sacculated aneurysm

Aneurysm in which there is weakness on one side of the vessel; usually due to trauma. It is attached to the artery by a narrow neck.
See: aortic aneurysm for illus.

varicose aneurysm

Aneurysm forming a blood-filled sac between an artery and a vein.

venous aneurysm

Localized expansion and weakening of the wall of a vein.
Medical Dictionary, © 2009 Farlex and Partners




dilation of an artery wall, a sac formed by abnormal dilation of the weakened wall of a blood vessel.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005