Aortic dissection and abdominal aortic aneurysms (AAAs) are important causes of morbidity and death that require rapid diagnosis and frequently require prompt operative repair to offer the patient any chance of survival. Diagnosing these conditions can be challenging and carries a high risk of misdiagnosis.
Four clinical scenarios arise regarding AAAs: acute rupture, aortoenteric fistula, chronic contained rupture, and an incidental finding. Although there are several other nonaortic large artery aneurysms that often require surgical repair by a vascular surgeon, they are aptly covered in Tintinalli's Emergency Medicine, 7th edition.
Acute rupturing AAA is a true emergency that, if not rapidly identified and repaired, will lead to death. The classic presentation is of an older (>60 years) male smoker with atherosclerosis who presents with sudden onset severe back or abdominal pain, hypotension, and a pulsatile abdominal mass. Patients may present with syncope or some variation of unilateral flank pain, groin pain, hip pain, or pain localizing to one quadrant of the abdomen.
Fifty percent of patients describe a ripping or tearing pain that is severe and abrupt in onset. Patients may have a tender pulsatile abdominal mass on physical examination, but the absence of pain does not imply an intact aorta. Obesity may mask a pulsatile abdominal mass. Nausea and vomiting are commonly present.
Shock may persist through presentation or may transiently improve due to compensatory mechanisms. Femoral pulsations are typically normal. Retroperitoneal hemorrhage may be appreciated as periumbilical ecchymosis (Cullen sign), flank ecchymosis (Grey-Turner sign), or scrotal hematomas. If blood compresses the femoral nerve, a neuropathy of the lower extremity may be present.
Aortoenteric fistulas, although rare, present as gastrointestinal bleeding, either a small sentinel bleed or massive life-threatening hemorrhage. A history of previous aortic grafting (eg, AAA repair) increases the suspicion. Because the duodenum is the usual site of the fistula, the patient may present with hematemesis, melenemesis, melena, or hematochezia.
Chronic contained rupture of AAA is an uncommon presentation. If an AAA ruptures into the retroperitoneum, there may be significant fibrosis and a limiting of blood loss. The patient typically appears quite well and may complain of pain for an extended period.
Discovering a previously undiagnosed asymptomatic AAA on physical or radiologic examination can be lifesaving. Those aneurysms larger than 5 cm in diameter (outer wall to outer wall) are at a greater risk for rupture, but all should be referred to a vascular surgeon.
Diagnosis and Differential
Although the diagnosis may be relatively straightforward in the setting of syncope, back pain, and shock with a tender pulsatile abdominal mass, the differential diagnosis varies depending on the presentation. Missed AAAs are most frequently misdiagnosed as renal colic. This life-threatening disease process should be considered in the differential diagnosis for any patient that presents with back pain, an intraabdominal process (pancreatitis, ...