AAA Diagnosis

[placebo_B12]

Do you need a contrast enhanced CT to diagnose a clinically significant AAA?

Many elderly patients with vague abdominal/back pain are not candidates for IV contrast due to reduced GFR, so I generally order a non-contrast CT to rule it out. Of course, if I am entertaining Aortic Dissection then I will either contrast enhance the CT or order an US/Echo. Does anyone do anything different?

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[NateintheED]

We do it a couple different ways. First, remember that AAA's develop over time. If your patient has had a recent abdominal CT with a normal aorta, then you're pretty much done. Second, like you said, if you're JUST looking for AAA, then non-contrast CT is probably fine. We do them frequently to look for kidney stones or other things in people with marginal kidneys, so you sort of get a "double rule-out" with that one. Finally, at least at our place, we do ED ultrasound for AAA. It can be a pretty easy scan, especially if you've got a relatively thin old person.

So no, I don't think you need a contrast CT to diagnose AAA. In fact, if you do u/s, then you don't need a CT at all.

 

[TysonCook]

last two I diagnosed where on US, then we d/w Nephro and CT what to do as far as further imaging (ie in the chest).

T

 

[southerndoc]

As Tyson said, you can diagnose with ultrasound. To see if it's actually leaking requires a contrast-enhanced CT (to look for active extravasation), but a non-contrast CT can find RP bleeding.

On another note, it is incredibly rare to have an isolated aortic dissection in the abdomen. Nearly every abdominal aortic dissection starts somewhere in the chest. So the patient will more than likely have chest and abdominal pain.

 

[docB]

I do a lot of non-contrast CTs on back pains over 50. As Southern mentions it tells me if theres fractures, stones an if there's a AAA as well as huge bladder and hydro from BPH and retention, lower lobe pneumonias, etc. I worry less about the radiation as the risk of developing a cancer 40 years down the line is less than it is in a 20 year old.

The CT will tell you if there is a AAA, however, it will not tell you if it's dissecting or bleeding (unless it's a really big bleed) without contrast. When I'm working a back or flank pain I go non con. If it's a crappy looking old guy with abd pain and hypotension I go with con.

Before everyone jumps on me about US, I know. But our US program is just getting going and we only have it in one hospital out of 5 so far. My practice with this will probably change as we get better US capabilities.