Abdominal Aortic Aneurysm

Rupture of an abdominal aortic aneurysm is a lethal condition that will be more frequently encountered as the population ages (see Chap 54). The incidence of abdominal aortic aneurysm in men increases rapidly after age 55 and peaks at the age of 80 at 5.9 percent. In women, the incidence rises quickly after age 70, peaking at 4.5 percent at age 90.22 Early detection and elective repair are associated with a mortality rate of about 4.0 percent. The mortality rate among those who reach the hospital is generally on the order of 50 percent or higher. A favorable outcome depends on a rapid diagnosis and early operative intervention. Unfortunately, initial misdiagnosis is common, occurring in 30 percent of patients in one series. 11

The most common symptom is abdominal pain, occurring in 70 to 80 percent, and not back pain, which is noted by just over half. The typical pain is sudden and significant. Atypical locations include the hips, inguinal area, and external genitalia. Syncope may be part of the presenting picture with or without significant blood loss from the aneurysm. Because of the lethal nature of this condition, the diagnosis should be considered in any older patient, especially male, with back, flank, or abdominal pain. Hypotension occurs at some point in the majority of these patients. Palpation of a tender, enlarged (>5 cm) aorta is the key physical finding. Unfortunately, the size of the aorta is often difficult to determine on examination.

Management of the unstable patient with a clinically suspected ruptured abdominal aortic aneurysm involves immediate operative intervention without confirmatory testing. A supine plain radiograph of the abdomen will often reveal a clue to the diagnosis, such as a calcified aortic outline or loss of the renal or psoas outline. In the stable patient, ultrasonography can delineate the size of the aorta, while computed tomography gives more information regarding actual rupture. 22 Any such testing should be expeditious and must include careful monitoring of the patient's condition, with appropriate alerting of the operating theater and surgical team.

The most common diagnostic mistake is to diagnose renal colic in these patients. This is understandable given the severe pain and the location of the pain. Furthermore, abdominal aortic aneurysm may present with hematuria. It should be axiomatic that aortic aneurysm be strongly considered in any patient over the age of 50 suspected of having renal colic. An episode of hypotension is often wrongly ascribed to developing sepsis or a "vagal" reaction in patients initially misdiagnosed as having renal colic.11

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