Abdominal aortic aneurysms (AAA) cause thousands of deaths annually, many of which could be prevented with timely diagnosis and treatment. AAA can be asymptomatic for many years, but in the one third of patients whose aneurysms rupture, the mortality rate is 80 percent. In the past, palpation of the abdomen was the preferred method for identifying AAA; however, diagnostic imaging studies, such as computed tomographic scanning and ultrasonography, are more accurate and have become the methods of choice. Palpation is now limited to identification of patients who need imaging studies to confirm the diagnosis. Lederle and Simel searched the literature to evaluate the safety and accuracy of attempts to diagnose AAA through physical examination.
Relevant studies with more than 10 patients that were published after 1966 were included in the literature search. An AAA was defined as an aortic diameter of at least 3 cm (sometimes 4 cm). Two studies that provided results by age and gender indicated that abdominal palpation had the highest positive predictive value in asymptomatic men over 60 years of age, while examinations of women and younger men had lower predictive values. Several studies emphasized that routine abdominal palpation differs from that designed to identify AAA. In one study, use of routine abdominal palpation led to a missed diagnosis in all patients who were subsequently diagnosed with ultrasound examinations. Other studies indicate that the sensitivity of abdominal palpation increases as aortic diameter increases, ranging from 29 percent for diameters up to 3.9 cm to 76 percent for those greater than 5 cm. However, the lack of a widened aorta does not rule out AAA. Obesity appears to limit the effectiveness of abdominal palpation, as detecting AAA is more difficult in patients with greater abdominal girth.
The proper technique for detecting an AAA with abdominal palpation begins with placing the patient in a supine position with the knees raised and the abdominal muscles relaxed. The aortic pulse can be palpated just above and to the left of the umbilicus. The width of the aorta can then be measured by placing both hands palms down on the patient's abdomen, with one index finger on either side of the aorta. Each systole should move the fingers apart. Note that initially it is easier to palpate one side at a time. The width of the aorta is the key finding, not the intensity of the pulsation; intensity does not confirm or disprove the presence of an AAA. Patients with an aortic diameter of greater than 2.5 cm require additional diagnostic studies, usually ultra-sonography. Abdominal palpation is not associated with an increased risk of rupture.
The authors conclude that physical palpation to detect AAA in asymptomatic patients under 50 years of age is not warranted. Abdominal palpation detects fewer than one half of the AAAs in high-risk patients and even fewer in low-risk patients, but those detected are likely be large enough to warrant surgery. In addition, palpation is not reliable enough to rule out the diagnosis; therefore, further diagnostic studies should be ordered in patients for whom there is a high index of suspicion.