An aortic aneurysm is an enlargement (dilatation) of the aorta to greater than 1.5 times normal size. They usually cause no symptoms except when ruptured. Occasionally, there may be abdominal, back, or leg pain. The prevalence of abdominal aortic aneurysm ("AAA") has been reported to range from 2 to 12% and is found in about 8% of men more than 65 years of age. The mortality rate attributable to AAA is about 15,000 per year in the United States and 6,000 to 8,000 per year in the United Kingdom and Ireland. Between 2001 and 2006, there were approximately 230,000 AAA surgical repairs performed on Medicare patients in the United States. The etiology remains the topic of continued investigation. Known causes include trauma, infection, and inflammatory disorders. Risk factors include cigarette smoking, advanced age, dyslipidemia, hypertension, and coronary artery disease. The pathophysiology of the disease is related to an initial arterial insult causing a cascade of inflammation and extracellular matrix protein breakdown by proteinases leading to arterial wall weakening. They are most commonly located in the abdominal aorta, but can also be located in the thoracic aorta. Aortic aneurysms result from a weakness in the wall of the aorta and increase the risk of aortic rupture. When rupture occurs, massive internal bleeding results and, unless treated immediately, shock and death can occur. Screening with ultrasound is indicated in those at high risk. Prevention is by decreasing risk factors, such as smoking, and treatment is either by open or endovascular surgery.
Rupture may be indicated by the presence of free fluid in the abdomen. A contrast-enhanced abdominal CT scan is the best test to diagnose an AAA and guide treatment options.Only 10–25% of patients survive rupture due to large pre-and postoperative mortality. Annual mortality from ruptured aneurysms in the United States is about 15,000. Most are due to abdominal aneurysms, with thoracic and thoracoabdominal aneurysms making up 1% to 4% of the total. Aortic rupture
An aortic aneurysm can rupture from wall weakness. Aortic rupture is a surgical emergency and has a high mortality even with prompt treatment. Weekend admission for a ruptured aortic aneurysm is associated with increased mortality compared with admission on a weekday, and this is likely due to several factors including a delay in prompt surgical intervention. Risk factors
Coronary artery disease
Hypertension
Loeys-Dietz Syndrome
Hypercholesterolemia
Hyperhomocysteinemia
Elevated C-reactive protein
Tobacco use
Alcohol use
Peripheral vascular disease
Marfan syndrome
Ehlers-Danlos type IVO
Bicuspid Aortic Valve
Syphilis
IgG4-related disease
Pregnancy
Chronic obstructive sleep apnea
Psoriasis

Pathophysiology
An aortic aneurysm can occur as a result of trauma, infection, or, most commonly, from an intrinsic abnormality in the elastin and collagen components of the aortic wall. While definite genetic abnormalities were identified in true genetic syndromes (Marfan, Elher-Danlos and others) associated with aortic aneurysms, both thoracic and abdominal aortic aneurysms demonstrate a strong genetic component in their aetiology. Prevention
The risk of aneurysm enlargement may be diminished with attention to the patients blood pressure, smoking and cholesterol levels. There have been proposals to introduce ultrasound scans as a screening tool for those most at risk: men over the age of 65.