AAA dx question

[sophiejane]

I'm on the last stretch of step 2 study and finding discrepancies between sources (probably means it's time to stop studying....)

Anyway, some say abd US for dx of pulsatile abd mass, some say CT. I always thought it was abd US. Of course, the person who says to do a CT in their review book is a radiologist ($$$)

what do you guys do?

thanks

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[southerndoc]

CT is a better exam that allows you to see the entire aorta. It's more expensive than ultrasound.

Ultrasound is a good screening test, and is the test of choice for any hypotensive patient. You can do one quickly at the bedside. Of course, ultrasound is limited by body habitus. You can scan a thin person with ease, but get some 350 pound guy and you may not even see the aorta. Likewise, large amounts of bowel gas can get in the way of seeing the aorta well.

So, both are correct ways of assessing for aortic aneurysms. Although more expensive, the CT is a better choice since it overcomes body habitus, bowel gas, etc., and can also allow you to see if there is active bleeding/rupture into the retroperitoneal space.

 

[NinerNiner999]

CT can also show with greater detail whether there are leaks in the aorta which may determine emergent surgery...

 

[WilcoWorld]

slightly off topic, but...

I had a patient the other night who had abdominal pain. She also had a AAA, an incarcerated ventral hernia (though it didn't appear strangulated), gallstones with elevated LFT's, and a raging case of pancreatitis.

What would you like to do with that one?

Since her vitals were stable & she wasn't puking, we laid our bet on gallstone pancreatitis, but not without several consults of course!

But to the OP, I agree with the above. If the patient's BP is low & getting lower, a AAA seen on bedside US is enough to earn a trip to the OR. If the patient is relatively stable, however, than a CT will give you a lot more information & will make your vascular surgeon a lot happier.

 

[sophiejane]

Thanks for your replies.

So, you think it's safe for the test if they ask what to do next, and US and CT are both listed, to choose US?

 

[deleted87716]

So, you think it's safe for the test if they ask what to do next, and US and CT are both listed, to choose US?

US is the preferred initial imaging study to screen for AAA in the nonobese patient. Use CT of the abdomen and pelvis, with contrast, if your patient is obese, or if you're worried about rupture or dissection.

 

[f_w]

If the patient is relatively stable, however, than a CT will give you a lot more information & will make your vascular surgeon a lot happier.

Also, some institutions are trying to go to emergent endovascular repair (survival for rupture+open repair is still dismal. there is some potential to improve on that with endovascular repair). For that, you need the CTA to select your equipment.

For the open surgical repair, the location of the leak doesn't really make a difference. The surgical approach pretty much remains the same.

(in our ER everyone seems to get a CT, regardless of clinical details of the picture. I am not kidding you, but requests of 'r/o cholecystitis vs AAA vs appendicitis vs kidney stones' are not unheard of.)

 

[deleted87716]

requests of 'r/o cholecystitis vs AAA vs appendicitis vs kidney stones' are not unheard of.)

Kinda makes you wonder if the ordering physician has even examined the patient yet, doesn't it?

 

[sophiejane]

Kinda makes you wonder if the ordering physician has even examined the patient yet, doesn't it?

well, now, I can see how someone might confuse colicky unilateral back pain with tearing central back pain...

er, on second thought...no I can't.

Hell, if you don't have time to take the history, just order the most expensive imaging test and you should be able to figure it out, right?

 

[sophiejane]

US is the preferred initial imaging study to screen for AAA in the nonobese patient. Use CT of the abdomen and pelvis, with contrast, if your patient is obese, or if you're worried about rupture or dissection.

Ah, right...that's what I was looking for...thanks, Kent.

 

[Hawkeye Kid]

for boards (and in general) remember to never send an unstable pt to radiology. if they give you a pt with suspected AAA and unstable vitals, AMS, etc, (bedside) US is probably the right answer.

 

[BKN]

well, now, I can see how someone might confuse colicky unilateral back pain with tearing central back pain...

er, on second thought...no I can't.

Hell, if you don't have time to take the history, just order the most expensive imaging test and you should be able to figure it out, right?

Sophie, read the lit. AAA is famous for mimicking renal colic, mechanical back pain, or abdominal pain in any quadrant. Also, refer you to a paper by Bob Gerhardt and me in AJEM in the last year. We used decision tree software to look at clinical data, lab data, plain imaging and CT for nonspecific abd pain. It was very painful to me as a old clinician who is proud of his skills to be beaten down by the machine, but there it is.

Am J Emerg Med. 2005 Oct;23(6):709-17. Links
Derivation of a clinical guideline for the assessment of nonspecific abdominal pain: the Guideline for Abdominal Pain in the ED Setting (GAPEDS) Phase 1 Study.

• Gerhardt RT,
• Nelson BK,
• Keenan S,
• Kernan L,
• MacKersie A,
• Lane MS.

Department of Emergency Medicine, Brooke Army Medical Center/San Antonio Uniformed Services Health Education Consortium, Fort Sam Houston, TX 78234, USA. [email protected]

OBJECTIVE: The purpose of this study was to identify a clinical guideline for the evaluation of nonspecific abdominal pain (NSAP) using history, physical examination, laboratory analysis, acute abdominal series (AAS) radiographs, and nonenhanced helical computed tomography (NHCT) clinical predictor variables (CPVs). SETTING: The setting of this study was at an urban emergency department (ED) with 70,000 yearly visits. METHODS: This is an institutional review board-approved, prospective, observational study. The primary outcome variable was urgent intervention (UI), defined as a diagnosis requiring surgical or medical treatment to prevent death or major morbidity. Subjects underwent prompted history, physical, laboratory studies, AAS, and NHCT and were followed up to 6 months for ultimate diagnosis and outcome. CPVs were subjected to classification and regression tree analysis. RESULTS: One hundred sixty-five subjects were analyzed. Thirteen percent of subjects required UI within 24 hours of presentation; an additional 34% underwent elective interventions that mitigated morbidity or mortality. Four guideline models were generated. Model 1 consisted of history and physical, with a sensitivity of 25%, a specificity of 92%, a positive likelihood ratio of 3.17, and a negative likelihood ratio of 0.81. Model 2 consisted of model 1 with laboratory, with a sensitivity of 39%, a specificity of 88%, a positive likelihood ratio of 3.25, and a negative likelihood ratio of 0.69. Model 3 consisted of model 2 with AAS, with a sensitivity of 56%, a specificity of 81%, a positive likelihood ratio of 2.94, and a negative likelihood ratio of 0.54. Model 4 comprised all inputs, including NHCT, with a sensitivity of 92%, a specificity of 90%, a positive likelihood ratio of 9.2, and a negative likelihood ratio of 0.089. NHCT was the single most accurate CPV for UI. CONCLUSIONS: No clinical guideline was identified exclusive of NHCT that possessed adequate sensitivity for exclusion of UI. NHCT is a rational choice for decision support in the evaluation of NSAP and is likely the single most useful diagnostic adjunct available to augment the clinical evaluation.

PMID: 16182976 [PubMed - indexed for MEDLINE]

 

[USAF MD '05]

Yep- this guy is one of my attendings. He is also our research coordinator. Kind of long winded on rounds and during a shift, but he really knows his stuff. Steve

 

[sophiejane]

Oh, OK, BKN. I'll get right on reading that literature as soon as I have memorized all the minute little pieces of info I have to know in 48 hours for Step 2.

After that, reading your article will be at the top of my to do list, I promise.

Good to know about AAA mimicking renal colic (I knew about it mimicking other sources of back pain but never heard of renal colic specifically)--I had actually never heard that (even though it's famous, apparently). One more thing on the long list of things I didn't know...sigh...

 

[f_w]

Kinda makes you wonder if the ordering physician has even examined the patient yet, doesn't it?

A lot of things make you wonder.

for boards (and in general) remember to never send an unstable pt to radiology.

For the boards: yes.

In reality: Don't send an unstable patient to radiology without at least one qualified staff member going along and without lines and monitoring in place and whatever liquid of your choice running. The deaths in the CT scanner tended to be patients wheeled from the ED to rads and parked in front of CT to wait for the tech to come in (in the days before 24hr CT coverage). Also, back then scanning an abdomen took 25minutes of scan time creating the delays that impact survival in acute trauma or suspected AAA negatively. Today, the scan itself takes 12 seconds and often the CT scanner is located IN the emergency department, as a result the equation has changed. So, I wouldn't get too dogmatic about this.

 

[southerndoc]

Oh, OK, BKN. I'll get right on reading that literature as soon as I have memorized all the minute little pieces of info I have to know in 48 hours for Step 2.

After that, reading your article will be at the top of my to do list, I promise.

Good to know about AAA mimicking renal colic (I knew about it mimicking other sources of back pain but never heard of renal colic specifically)--I had actually never heard that (even though it's famous, apparently). One more thing on the long list of things I didn't know...sigh...

Although it's probably none of my business, I can't figure out if you're seriously interested in reading his article, or if you just don't care.

An internet discussion forum can be misleading without a tone of voice to judge what a person's intentions are with his or her statements. The sense I get from your post is that you could care less about AAA's and how renal colic type pain can be an AAA.

 

[sophiejane]

Although it's probably none of my business, I can't figure out if you're seriously interested in reading his article, or if you just don't care.

An internet discussion forum can be misleading without a tone of voice to judge what a person's intentions are with his or her statements. The sense I get from your post is that you could care less about AAA's and how renal colic type pain can be an AAA.

You did misinterpret...lighten up there a bit, doc.

I was being a little bit sarcastic because I am taking Step 2 tomorrow and as I said in my reply to BKN, don't really have time to read primary literature right now as he suggested I do, but I did thank Dr. Nelson for the information, as I did all of you. I had honestly never heard about the renal colic/AAA connection specfically and appreciated the reference.

If I didn't care about how to dx AAA I would not have started the thread. It is something I've seen differing info on and I was confused, but thanks to this great online community (and I'm not being sarcastic) I got it cleared up.

 

[BKN]

You did misinterpret...lighten up there a bit, doc.

I was being a little bit sarcastic because I am taking Step 2 tomorrow and as I said in my reply to BKN, don't really have time to read primary literature right now as he suggested I do, but I did thank Dr. Nelson for the information, as I did all of you. I had honestly never heard about the renal colic/AAA connection specfically and appreciated the reference.

If I didn't care about how to dx AAA I would not have started the thread. It is something I've seen differing info on and I was confused, but thanks to this great online community (and I'm not being sarcastic) I got it cleared up.

Well I took it the way you intended. No problem. Good luck on step 2!

BN