CT: contrast vs. non-contrast

[draino15]

Anyone know the indications for each.
ie...brain trauma = get non-contrast. infection = contrast.
are those even correct?

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[Whisker Barrel Cortex]

Head CT:

Non contrast for trauma, headache, stroke. Pretty much most things.

Contrast is utilized for evaluation for infection (menigeal enhancement, abcess) or tumor (mets). However, contrast enhanced head CT is significantly inferior to MRI for these indications and we do very few contrast enhanced head CTs. (The only exception is CT angiogram of the head for evaluation of aneurysm, thrombosis, or dissection.)

Chest CT:

Non-contrast: Lung parenchymal evaluation. E.G. Lung nodules, interstitial lung disease.

Contrast: Evaluation of the mediastinum (lymph nodes, infection). Evaulation of the vascular structures or heart (CT Angiogram of pulmonary arteries for PE,aorta for dissection, trauma, aneurysm, coronary CT). Some role in infection (if pleural effusion, helpful to eval for empyema, if cavitary lesion, helpful to eval for lung abcess or lung necrosis). Useful in unusual lesions.

Abd/Pelvis:

Non-contrast: Only common reason to order this is to look for calculi in the kidneys or ureters (the other common indication is severe contrast allergy) Contrast enhanced scans can obscure calculi if the contrast is beginning to get excreted already. There is no need for oral for this scan.

Contrast: Pretty much everything else. Appy (although a few centers do this without contrast), pancreatitis (essential), diffuse abdominal pain, abcess, diverticulitis, liver mass, etc etc. Anything you can think of. We can make some of these diagnoses without contrast, but having it on board makes us better. For the majority of indications, oral contrast helps too.

CT angiogram: This is just a contrast enhanced CT with a faster bolus and timing of the scan on the arterial system. Useful for eval of the aorta, mesenteric vessels, renal arteries, etc.

With and Without: Only a couple indications. Hematuria evaluation (non con to look for stones, contrast to look for renal masses, delays to look for ureteral or bladder lesions). Evaluation of a incidental adrenal mass to see if you can prove its an adenoma and not badness. Can't think of any other common reasons.

Hope that helps.

 

[MadameLULU]

thanks for the summary!

When I was in the ER we would order CT Abd/pelvis with triple contrast, but I've forgotten why it was "triple"? Can you explain?

 

[FuzzyBK]

Triple = iv + oral + rectal

 

[hyrule]

Is there a logical way you can think about contrast vs. non-contrast?

For ex, with head, you don't use contrast b/c you don't want to risk hemorrhage. For tumors, it makes sense because it indicates leaky vasculature.

But what about everything else?

 

[colbgw02]

Is there a logical way you can think about contrast vs. non-contrast?

For ex, with head, you don't use contrast b/c you don't want to risk hemorrhage. For tumors, it makes sense because it indicates leaky vasculature.

But what about everything else?

I'm not aware of any increased risk for ICH with contrast. The reason noncontrast head CTs are done is because the contrast can decrease sensitivity. A tiny bright spot (i.e. bleed) can easily get missed because of the vessels lighting up. In the setting of trauma, a noncontrast exam is sufficient and cheaper. If there are findings on the noncontrast, then you can always give contrast and re-image. Specifcally for head CTs, a contrast examination is typically preceded by a noncontrast one.

In general, if you're dealing with an -itis or an -oma, then contrast is indicated. There's a ton of variation though, so if you're unsure, it's best to just pick up the phone and ask the radiologist.

 

[dienekes88]

I'm not aware of any increased risk for ICH with contrast. The reason noncontrast head CTs are done is because the contrast can decrease sensitivity. A tiny bright spot (i.e. bleed) can easily get missed because of the vessels lighting up. In the setting of trauma, a noncontrast exam is sufficient and cheaper. If there are findings on the noncontrast, then you can always give contrast and re-image. Specifcally for head CTs, a contrast examination is typically preceded by a noncontrast one.

In general, if you're dealing with an -itis or an -oma, then contrast is indicated. There's a ton of variation though, so if you're unsure, it's best to just pick up the phone and ask the radiologist.

This.

Acute blood is hyperdense (white) on CT. If you give contrast, you won't be able to see anything.

 

[drizzt3117]

I think the easiest way to think about it is to think about what scans are given without contrast (typically just kidney stones and ICH/SAH eval) and assume contrast is preferred for everything else unless there's a contraindication.

 

[hyrule]

I think the easiest way to think about it is to think about what scans are given without contrast (typically just kidney stones and ICH/SAH eval) and assume contrast is preferred for everything else unless there's a contraindication.

For kidneys, is it because contrast is renally excreted through the kidneys anyways, resulting in hyperdensity regardless of a lesion?

 

[colbgw02]

For kidneys, is it because contrast is renally excreted through the kidneys anyways, resulting in hyperdensity regardless of a lesion?

I'm not really sure what this is supposed to mean, but again, the issue is one of sensitivity. Stones are typically dense, so is contrast. It's easier to see the bright stone when nothing else nearby is bright. The phase of contrast also matters; an excretory phase will decrease sensitivity for ureteroliths more so than one performed during the corticomedullary or nephrographic phases. That is why a renal stone protocol CT is usually included with a CT IVP/CT urogram (or whatever they call it at your institution).

 

[drizzt3117]

For kidneys, is it because contrast is renally excreted through the kidneys anyways, resulting in hyperdensity regardless of a lesion?

I'm not sure if you're referring to a CT urogram or a CT flank pain (non-con) but it has to do with what you're trying to visualize, whether it's a kidney stone or renal parenchyma or collecting system.