An abdominal aortic aneurysm (AAA) may be asymptomatic until it ruptures or may present with abdominal discomfort and a pulsatile mass noted by the patient. There tends to be a family history and thus screening is appropriate in such families. Ultrasound screening is advisable in first-degree relatives over 50 years.
The risk of rupture is related to the diameter of the AAA and the rate of increase in diameter. The normal diameter of the abdominal aorta, which is palpated just above the umbilicus, is 10-30 mm, being 20 mm on average in the adult; an aneurysm is greater than 30 mm in diameter. Greater than 50 mm is significantly enlarged and is chosen as the arbitrary reference point to operate because of the exponential rise in risk of rupture with an increasing diameter. Refer all cases. The patency of a dacron graft after 5 years is approximately 95% (Fig 30.7).
Diameter in tm
Fig. 30.7 Guidelines for normal and abnormal widths of the abdominal aorta in adults (to exact scale)
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