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CT Necessary?

Discussion in 'Medical Students - MD' started by kdburton, Jun 20, 2008.

  1. kdburton

    kdburton Ulnar Deviant
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    Can anyone give me some examples of conditions in the emergency department where CT scan is one of the (or even the main) diagnostic tools, but for which there are other tests with comparable sensitivity and specificity? So far I'm thinking acute appendicitis and maybe abdominal aortic aneurysm... I'm searching for articles on the topic and have limited knowledge. Thanks for any help.
     
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  3. soeagerun2or

    soeagerun2or Membership Revoked
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    Head trauma/CVA. There may be focal neurological deficits or papilledema but imaging is necessary before surgery.
     
  4. ZagDoc

    ZagDoc Ears, Noses, and Throats
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    Agreed. Any sort of injury where increased ICP is present. Also brain abscess or encephalitis. LP could risk brainstem herniation.
     
    #3 ZagDoc, Jun 20, 2008
    Last edited: Jun 20, 2008
  5. The Angriest Bird

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    In modern hospitals, most solid neoplasms will trigger a CT scan.
     
  6. dynx

    dynx Yankee Imperialist
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    nephrolithiasis
    any tumor
    any clot of abdominal vessels (before angio)
     
  7. Dakota

    Dakota Senior Member
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    As others have mentioned with the head: Subarachnoid hemorrhage, lumbar puncture.
     
  8. vtucci

    vtucci Attending in Emergency Medicine
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    General rule: CTs are quick and easy to perform and take a mere fraction of the time of MRIs.

    Head CTs are generally done first in cases of trauma/stroke/increased intracranial pressure to r/o bleeding. For example, if a patient had a hemorrhagic stroke, you would not want to give them TPA.

    Abdominal/pelvic CT can be done in cases for example if ultrasound is equivocal or cannot visualize the appendix well in a possible appendicitis (as you mentioned). Also, FAST ultrasound is often used to assess for abdominal trauma but abdominal CTs are frequently taken as well.

    Helical CT- Pulmonary embolus

    If you are looking for specific articles, you can start with google scholar and pubmed.
     
  9. AmoryBlaine

    AmoryBlaine the last tycoon
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    Small semantic point: "CVA" is considered a) an outdated term and b) not reflective of the underlying pathology. Call them strokes.
     
  10. PeepshowJohnny

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    Or "Brain attack" :rolleyes:
     
  11. soeagerun2or

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    I chose that particular terminology specifically so as to not discern between stroke, TIA, aneurysm, or AVM.
     
  12. AZhopeful

    AZhopeful Natural Killer Cell
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    Didn't the OP ask for conditions where there was another test with similar sensitivity/specificity to CT?
     
  13. colbgw02

    colbgw02 Delightfully Tacky
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    A shorter list would be the conditions seen in the ER that don't lead to a CT scan.
     
  14. kdburton

    kdburton Ulnar Deviant
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    Yes, AZhopeful thats what I asked for, but I'm not sure how many of the replies fit that criteria:laugh:. I'm doing a literature review on the [over]use of CT scans on emergency room patients. For instance, the hospitals affiliated with the school I attend will almost always end up doing a nonenhanced and a contrast-enhanced (IV+oral) CT scan on someone who comes in with undifferentiated abdominal pain. Although CT has many benefits in this situation, there are also risks that [as studies have shown] many doctors are not fully aware of and then never get conveyed to the patients. At the same time there are sometimes other diagnostic tools with less radiation risk for example that, although maybe less sensitive and specific for diagnosing common causes of this presentation, carry less risk. The risks and benefits must be weighed and my lit review will try to get that discussion going. Its pretty specific as far as I'm trying to address only emergency department patients and it will probably only be those presenting with undifferentiated abdominal pain, but they make up a decent percentage of patients in the ED anyways
     
  15. Neuronix

    Neuronix Total nerd
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    Non-contrast CT and MRI now have comparable sensitivity and specificity for acute intracranial haemorrhage.
     
  16. vtucci

    vtucci Attending in Emergency Medicine
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    noncontrast CT will be quicker and cheaper though.
     
  17. Neuronix

    Neuronix Total nerd
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    This is an evolving and controversial area right now. I will briefly present the ultra-academic side of the argument that may become clinical reality in say 10 years. To state it simply, MRI has the possibility of taking over CT in the setting of acute stroke diagnosis. See for example:

    http://stroke.ahajournals.org/cgi/content/full/36/9/1939
    MRI Screening Before Standard Tissue Plasminogen Activator (rtPA) Therapy Is Feasible and Safe

    The main argument as you stated is yes, CT is faster and cheaper in the setting of stroke. But, a MR stroke protocol can be done in 20 minutes at experienced academic centers. This is mostly because you want to get multiple contrast mechanisms while CT only gives structural information. Is the time and extra expense worth it? Maybe. The extra information allows you to make a better informed decision about how to treat the acute stroke patient. We know that MRI is more sensitive and specific to the cause of neurologic symptoms. That alone may make MRI worth it by more accurately selecting ischemic vs hemorrhagic strokes.

    But, there's an additional, an upcoming reason why MRI may become standard of care in this scenario. If MRI allows us to better select patients that may benefit from rtPA therapy during stroke, it is likely to become the standard of care in hyperacute stroke scenarios.

    See for example: http://stroke.ahajournals.org/cgi/content/full/36/1/66

    In this case they use the perfusion-diffusion mismatch to identify those patients that will benefit from rtPA therapy after the "3 hour window" that currently limits rtPA use. As you know, rtPA is a dangerous drug that can kill on its own due to the formation of hemorrhage. But, it is known that strokes still evolve after 3 hours in some patients and the 3 hour window probably is too restrictive.

    See: http://www.thelancet.com/journals/lancet/article/PIIS0140673604156924/abstract

    Further, there are also many patients in which the onset of stroke is unknown (due to confusion or waking up with symptoms) and so it is not know how much benefit rtPA will give if given. Due to the danger of rtPA, it is often not given.

    So if we had a technique that could select those patients whose strokes are still evolving after the 3 hour window or even better, could predict who still would benefit from rtPA even when time of onset is not known, the additional QALYs gained in stroke patients by selecting based on that information would likely make that technique cost-effective in this scenario. The PWI and DWI MRI may very well fill that niche (but it's not perfect either). A cost-benefit analysis of a larger trial is needed.

    This imaging of ischemic penumbra, by any imaging technique, is an active area of research. It's what I'm finishing my thesis on now. We have a very large grant to study oxygen consumption techniques specifically for this purpose--to identify those who will benefit from rtPA therapy.
     
  18. MSHell

    MSHell Deranged User
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    Wait a sec, you wrote before about non contrast = MRI in hemorrhagic stroke. Then in this last post you only talk about ischemic stroke. The dx and tx are different in both. Apples and oranges.
     
  19. Neuronix

    Neuronix Total nerd
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    The diagnostic scenario I'm referring to is often the same. A patient in the past few hours began having the signs of a stroke. Today, in a tPA capable center the question answered by CT scanning is to r/o hemorrhagic stroke so tPA can be given. MRI is currently at least as good as CT at detecting intracerebral hemorrhage if it is indeed hemorrhagic stroke.

    I wanted to point out that while in the present, CT IS cheaper and faster, in the future MRI's use may be expanded to not just r/o intracerebral hemorrhage in a stroke scenario. So yes if you use a very strict definition, for the diagnosis of hemorrhagic stroke they are roughly equal. But MRI gives you more information. That is likely to become more information that will guide treatment. But, I recognize this is a purely academic discussion for the interested more than it is current reality.
     
  20. brianmartin

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    I think some ER doctors are very good about considering alternatives to CT, and some are not. However you can run into trouble. Take for instance acute appy, where I believe ultrasound is around 85% specific and CT is 95%. Try calling a surgeon with a diagnosis of appendicitis by ultrasound. Surgeons want a CT scan because they don't want to waste an hour in the OR to find a non-acute abdomen. This used to happen much more often, and it was taken more lightly. Now with the availability of CT, surgeons feel they should never have to waste their time on a non-acute abdomen. And sure, US can miss appy too but think back to the time when every case was a clinical call. I think we can spare a few hours time to avoid irradiating people unnecessarily. People are over-scanned in the ER for a variety of reasons, mostly in cases like the above, and trauma patients.

    Other things are more of a gray zone. The d-dimer cutoff at 500 probably triggers way too many chest scans. A d-dimer of 550, chest pain of unknown cause, normal vital signs, and they get scanned. There is the option of a v/q scan but I'm not sure how much different the radiation exposure is. I think contrast CT is also more sensitive.
     
    #19 brianmartin, Jul 1, 2008
    Last edited: Jul 1, 2008
  21. radslooking

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    HEAD CT's
    falls in elderly--rule out subdural or epidural bleeds (intracerebral hemorrhage less commonly)

    trauma--rule out bleed, same as above

    decreased level of consciousness--rule out bleed, stroke, space occupying lesion (usually cancer), evidence of infection as the clinical situation suggests. A CT is a MUST pre-lumbar puncture to insure that signs of increased ICP are not present as this could cause life-ending herniation of brain components)

    * of note, head ct's miss 5% of subarachnoid hemorrhages. if this is suspected (sudden onset of severe headache with possible mental status changes) then lumbar puncture is needed to look for xanthochromia

    Chest CT's (with contrast) (also called chest CT angiogram)

    To rule out pulmonary embolus. This requires intravenous contrast, whereas most head CT's do not.

    Abdominal CT's-(Abdominal CT angiogram)
    -needed to look for abdominal pain with suspicion for mesenteric ischemia or clot

    Spiral CT-common to look for stones/nephrolithiasis

    Other common uses
    -Appendicitis (ultrasound also used...debate is to which is better)
    -CT angio of various vessels....subclavian, etc, if you suspect a clot in these areas.
    -Aortic CT (no contrast generally needed) to look for aortic dissection in patient with chest pain. Alternative is transesophageal echo.
    -CT's of abdomen also common to look for infections (abcesses), cancers, diverticulitis, obstruction (CT's identify where obstruction is in small bowel, large bowel, etc).

    Non-urgent uses:
    -CT's of various muskuloskeletal regions are also used--i.e. hip for fracture, pelvic for fractures. (mri's are somewhat more common for muskuloskeletal issues due to better soft tissue deliniation...i.e. acl tears, etc)

    One thing CT's are NOT used for. Is to confirm the presence of intrauterine pregnancy. ;) :thumbdown: Not unless you plan on interrupting organogenesis for a little while. :) Therefore, if it is a child bearing woman, run an HCG before you get the scan. :)
     

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