Abdominal aortic aneurysm: Clinical sciences

Abdominal aortic aneurysm, or AAA, is defined as aortic dilatation greater than 3 cm in diameter. Most AAAs are fusiform, which means they’re spindle shaped and involve the entire circumference of the aortic wall. Based on the symptoms, AAA can be symptomatic or asymptomatic. While most triple As are asymptomatic and found incidentally on imaging studies, all AAAs are at risk for expansion and rupture.

When a patient presents with signs and symptoms suggestive of AAA, you should first perform an ABCDE assessment to determine if the patient is stable or unstable. If the patient is unstable, start with acute management to stabilize their airway, breathing and circulation. This means you might need to intubate the patient, establish IV access, initiate fluid resuscitation, and manage the heart rate and blood pressure before continuing your workup.

Once you have initiated acute management, your next step is to obtain a focused history and physical. The important thing to determine here is whether they have a prior history of AAA. In an unstable patient with a known AAA, history might reveal sudden onset abdominal, back, or flank pain. Physical examination might show a pulsatile abdominal mass with generalized diffuse tenderness, as well as tachycardia and hypotension. If this is the case, suspect AAA rupture. Then get a surgical consult for emergent open repair. However, some patients with complex comorbidities might be poor surgical candidates, so you can consider endovascular repair. The exact diagnosis of rupture, dissection, or mass effect impinging upon other surrounding blood vessels will be made intraoperatively.

Alright, let’s go back to history and physical and talk about unstable patients without known AAA. They might also present with a history of sudden onset abdominal, back or flank pain, and have tachycardia, hypotension, as well as a pulsatile abdominal mass on exam. If so, you should perform a point-of-care ultrasound or POCUS to look for an aneurysm. There are a few things you might see here.

First, there might be a AAA with a rupture. Now, if the POCUS shows an abnormally dilated abdominal aorta with surrounding free fluid or extravasation of flow on doppler, it’s most likely an AAA with rupture. Make sure to order stat blood type and call for an emergent surgical consultation for surgical or endovascular repair. Do not delay intervention, as the risk of death by exsanguination is extremely high.

Next, you might see AAA with signs of dissection. In this case POCUS will show an aneurysm with an aortic wall flap, or a separation of the wall. If you see these findings, you can make a diagnosis of AAA with dissection. AAAs with isolated abdominal aortic dissections are rare, but they have a high risk of rupture as the separated part of the wall dies from the disrupted blood supply. Additionally, the dissected wall can impinge upon smaller aortic branches, like the renal or celiac arteries, and cut off the blood supply to vital organs. It may also affect blood supply to the bilateral lower extremities. Therefore, you must call for an urgent surgical consultation for surgical or endovascular repair.

Let’s switch gears and talk about the AAA itself. If the POCUS shows a AAA without any evidence of rupture or dissection, you can diagnose AAA. However, since the patient is hemodynamically unstable, you should remain suspicious for a rupture or dissection that the ultrasound could not detect. In this case, the patient needs urgent surgical consultation for surgical or endovascular repair, like aortic stent-graft placement to prevent a serious complication, or monitoring by the surgeon. Finally, if you see a normal abdominal aorta with no evidence of an AAA, consider alternate diagnoses like gastrointestinal bleeding or perforated peptic ulcer disease.