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28ANEURYSMCarotidArteryCoronaryArteryPlaque of atheromaAneurysmAbdominal Aortadivides intoIliac Arteriesto PelvisFIGURE 1Aneurysm.smokers and patients who never smoked by as much as afactor of 14 for smokers.Weakening of arteries may occur because of loss ofelasticity of the aortic wall due to aging. Another diseasethat affects the aortic wall is cystic medial necrosis, and thisappears histologically as smooth muscle cell necrosis anddegeneration of elastic layers within the media. The causeof the disease is unknown and mostly affects the thoracicaorta. Virtually all patients with Marfan syndrome developcystic medial necrosis disease and many, at a young age,develop aneurysms that occur mainly in the ascendingaorta, where the aorta originates from the heart.Studies indicate that there is a familial, genetic incidenceof abdominal aortic aneurysms. Screening of siblingsolder than 50 years of age of patients with aneurysmsrevealed an occult aneurysm in approximately 30% ofbrothers and less than 10% of sisters. The prevalence ofabdominal aortic aneurysms (3–6 cm) is approximately3 and 5% in individuals older than 55 and 65, respectively.The prevalence among men is about five times thatamong women. Studies suggest that one-time ultrasoundscreening of men at age 65 is sufficient to identify nearlyall those who are at risk. At this age men who have aorticdiameters less than 2.6 cm are all expected to be free fromsignificant aneurysm (less than 4 cm) 12 years later.B. Signs and SymptomsThe occurrence of abdominal aortic aneurysms is commonin men over age 55 and in women after age 70. Aneurysmsmay grow to more than 5 cm without causing symptomsand may go unnoticed by the individual. Abdominal aorticaneurysms, however, are not always asymptomatic. Backpain, abdominal pain, and particularly intermittent claudicationin men greater than age 65 may be the clue tothe presence of an abdominal aortic aneurysm. Selectivescreening for aneurysms in patients with intermittentclaudication nearly doubles the yield over screening in thegeneral population.The asymptomatic mass may be detected by deepmanual palpation of the central abdomen below or abovethe umbilicus. The majority of aneurysms are not detected