Indications for CT w/ contrast

[rs2006]

Hi everyone,
I hope all is well. I am a confused resident who would appreciate it if someone could clearly state the indications for a CT with contrast. Thank in advance for all of your responses.

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[Zweihander]

IV contrast increases the radiodensity of structures with a high amount of blood flow. In other words, because IV contrast goes into your blood vessels, tissues that either ARE blood vessels or are highly invested with them will be brighter than they are without contrast and also brighter than surrounding, relatively non-vascular tissue.

Since the technology of CTs and x-rays depends on visualizing the body by creating interfaces between structures of different densities, contrast CTs can both create interfaces and obliterate them. Thus, your indications and contraindications to CT with contrast studies depend on what tissues you are imaging and what you are trying to find.

In pancreatitis, for example, the normally vascular pancreas will "light up" on CT with contrast, but dead areas will not. This allows you to estimate degree of necrosis involved in an acute pancreatitis.

You can also image intraabdominal bleeds because the IV contrast will spill out of lacerations into the abdominal cavity, you can use the interfaces between dense and lucent created by contrast to image hyper- or hypovascular lesions (such as malignancies, which can be either, or abscesses, which are lucent), or you can use contrast studies to search for intravascular filling defects such as when searching for pulmonary embolism or trying to image an aortic dissection.

Hope that helps.

 

[Osteopathology]

From what I have seen employed....which I am unaware of if it is RIGHT or not:

CT with contrast as a standard exam via their protocol, unless the condition of the patient did not warrant its use. (creatinines clearance, risk of contrast leaving a defined area, etc)

I would aslo be curious as to OTHER conditions where one would elect to avoid its use.

Osteo

 

[Whisker Barrel Cortex]

Copy and Pasted from my previous response to this same question:

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.

 

[Caffiend_79]

The post by Whisker Barrel Cortex is pretty good.

The liver, pancreas, kidneys and adrenal glands have specific protocols that are used to optimize imaging these organs. When ordering a CT to specifically image one of these organs, you should order the corresponding organ protocol (e.g. order a "liver protocol" CT to image a liver mass).

Also, unless there is a contraindication, I think all adolescent and older abdominal pain cases need triple contrast. It drives me crazy when I get an acute abdominal pain case and no rectal contrast was given. Usually CT techs won't give rectal contrast unless the ordering physician specifically requests it.

One final abdominal imaging point, you should almost never order a CT of the abdomen without the pelvis and visa versa. If you're thinking of ordering just an abdomen or pelvic CT, I would advise discussing it with one of the radiologists.

 

[Zweihander]

One final abdominal imaging point, you should almost never order a CT of the abdomen without the pelvis and visa versa. If you're thinking of ordering just an abdomen or pelvic CT, I would advise discussing it with one of the radiologists.

Why is that?

I've run into this before -- I had a patient with a groin mass noted on u/s we wanted to further characterize, and initially we had ordered a CT pelvis and the radiologist called us up and told us to change it to abd/pelvis.

 

[colbgw02]

Also, unless there is a contraindication, I think all adolescent and older abdominal pain cases need triple contrast. It drives me crazy when I get an acute abdominal pain case and no rectal contrast was given. Usually CT techs won't give rectal contrast unless the ordering physician specifically requests it.

Are you being serious?

 

[Dr Chooch]

The post by Whisker Barrel Cortex is pretty good.

Also, unless there is a contraindication, I think all adolescent and older abdominal pain cases need triple contrast. It drives me crazy when I get an acute abdominal pain case and no rectal contrast was given. Usually CT techs won't give rectal contrast unless the ordering physician specifically requests it.

As an initial examination do you really think that is necessary for all those patients? For example, for the people who are presenting w/ acute abd pain that turns out to be an SBO - won't giving rectal contrast limit you in deciding whether it is a partial or complete obstruction (especially in distal SBO's)?

 

[f_w]

I've run into this before -- I had a patient with a groin mass noted on u/s we wanted to further characterize, and initially we had ordered a CT pelvis and the radiologist called us up and told us to change it to abd/pelvis.

If a known pathology is clearly limited to one territory or the other, it is counterproductive to add the additional test (added expense, added radiation).

Routinely adding the pelvis applies mostly to the workup of abdominal pain (doesn't really matter whether localized or generalized). Many of the structures (cecum, sigmoid) you are interested in in abdominal pain are actually in the pelvis. If you ordered a pelvis only otoh, you won't have the transverse colon included in the study.

 

[f_w]

Also, unless there is a contraindication, I think all adolescent and older abdominal pain cases need triple contrast. It drives me crazy when I get an acute abdominal pain case and no rectal contrast was given. Usually CT techs won't give rectal contrast unless the ordering physician specifically requests it.

While I like rectal contrast for cases that are specifically to evaluate for appendicitis (mostly for ER/surgical logistics reasons), I don't think it is a must. If you are patient enough to wait for oral contrast to percolate through, you will get the same answer with less discomfort/embarassment to the patient.
I also prefer to have IV contrast for appendicitis cases, it makes things easier. There is however literature out that doesn't support this with statistical evidence.

 

[Caffiend_79]

As an initial examination do you really think that is necessary for all those patients? For example, for the people who are presenting w/ acute abd pain that turns out to be an SBO - won't giving rectal contrast limit you in deciding whether it is a partial or complete obstruction (especially in distal SBO's)?[/QUOTE

I meant for cases of abdominal pain without a definite cause. If the CT scan is for something like a known abdominal mass or for known pancreatitis, I don’t think rectal contrast is needed. Appendicitis, colitis and diverticulitis are some of the most common causes of non-specific abdominal pain, and rectal contrasts aids in evaluating these entities. I don’t know why a clinician wouldn’t always entertain these diagnoses in a patient presenting with non-specific abdominal pain, so I don’t know why you would want to do a CT without rectal contrast in these patients.

I particularly think rectal contrast is important in vague abdominal pain cases with essentially negative abdominal CT scans. Non-distended or under distended colon frequently looks thickened; which leads to at least some overcalling of colonic wall thickening, especially in an otherwise negative CT scan because you want to find some explanation for the patient’s pain

I would put bowel obstruction in the same category as pancreatitis. I don’t think rectal contrast hurts my interpretation of the study, but it isn’t needed either. I’ve never had a surprise case of bowel obstruction, the clinician usually has a high index of suspicion for obstruction prior to the CT being ordered based on clinical hx and initial abdominal imaging.

 

[Docxter]

I agree with f_w re the need for rectal contrast. It's a logistic issue. The standard preferred way for diagnosing abd. pain overall is oral+IV contrast. Rectal contrast is given instead of oral for logistic reasons, so the patient (and ED) doesn't have to wait for two hours or so to rule out appy.

As for giving IV contrast, actually there is some literature that supports giving IV contrast for appendicitis cases with statistical evidence. e.g.,

Jacobs JE, et al. Acute appendicitis: comparison of helical CT diagnosis focused technique with oral contrast material versus nonfocused technique with oral and intravenous contrast material. Radiology. 2001 Sep;220(3):683-90.

 

[f_w]

As for giving IV contrast, actually there is some literature that supports giving IV contrast for appendicitis cases with statistical evidence. e.g.,

And this article (as well as about 20 others by the same author) make the case for rectal contrast only:

Rao PM, Rhea JT, Novelline RA, Mostafavi AA, Lawrason JN, McCabe CJ AJR Am J Roentgenol. 1997 Nov;169(5):1275-80.Helical CT combined with contrast material administered only through the colon for imaging of suspected appendicitis.

In addition to logistical reasons, there is actually a medical reason to use rectal contrast: 'Time is perforation' Adding 90minutes to the workup may increase your perf rat (---> and thereby increase mortality and morbidity of an otherwise very controllable condition).

This afternoon around 4 we had a 21 year old kid with abd pain and a 18k WBC count in our ER. After talking to the ER doc, we decided on rectal and IV, that way he could be in the OR before business closes for new years eve. His appendix was indeed hot and he was taken care of without undue delay.

 

[mtha26]

F_W :

Contrast enhanced CT in a 21 y.o. boy is not the the first thing we do if there are clinical signs of acute appendicitis in Europe. We do an ultrasound. It's noninvasive, faster, cheaper and without radiation. But sensitivity it is operator dependent though.

Don't get me wrong, I like CT, but not in that case.

I'm pediatric radiologist

Marty.

 

[f_w]

F_W :

Contrast enhanced CT in a 21 y.o. boy is not the the first thing we do if there are clinical signs of acute appendicitis in Europe. We do an ultrasound. It's noninvasive, faster, cheaper and without radiation. But sensitivity it is operator dependent though.

Sensitivity is not only operator dependent, it is also lower than that of a properly done CT. If your surgeon is willing to accept a negative ultrasound to send a patient home, then doing the US is useful. If he will insist on the CT anyway, the value of the US is very limited and it will only add expense and delay to the workup (unless of course it's positive, then it is of help).

One of the main reasons for doing CT in the US is the fact that everything you do has to be done in a way that it can stand up in court later on. An appy missed on US that goes on to perf is a big liability for everyone involved (ER doc, surgeon, radiologist). If I was back in europe, I would consider using more US for this application, in the medicolegal situation I am faced with here I can't.

Sensitivity for appy:
- ultrasound: 86%
- CT: 96%
- pediatric surgery fellows hands: 85%

 

[mtha26]

True, can't argue with that. Sooner or later we will also be doing tons of examinations just to cover ouselves...

M.

 

[spudboy]

"What is the right thing to do?"

I am kinda in a dilema as a CT tech wondering what is the right thing to do.
I will try and make this as short,sweet and to the point as much as I can.

I have been a CT tech and supervisor just shy of 20 yrs now. I feel that I do have alot of experience and knowledge when it comes to my profession. I worked with a group of excellent radiologist for about many yrs. They were very experienced,smart,proactive, great
with pateint care and so forth. They were part of a very large radiology group in a major city. I was able to work with them very close on a daily basis and was always
learning from them. When it came to CT scanning protocols they were very hands on
and helpful in doing what was right,according to them. Thats what I was taught and beleived in and seemed to me to be a very high standadrd of patient care when it comes to exposing people to radiation. Basically there was really no need for non contrast studies with a few exceptions(nodule follow ups, kidney stones, multi phase exams of liver,panc,renals,cta's, trauma heads are they few that come to mind). We rarely would scan some with and without for general abd pain(just with oral and IV) and definetly no delays unless a liver,renal lesion was seen.No sense in irradiating someone when it was not neccesary. Thats how we operated and the CT dept was ran. We had a protocol book in our scheduling dept on what was to be ordered(or suggested) when an office called in with a diagnosis when scanning . According to the radiologists having contrast gave more information, than what a non con could do(except for certain studies) so no sense exposing someone when it's not needed or would not be benefical.

I moved on to a different job as a regular staff CT tech. I work for another
very large group of radiologist. I expected things to be a little different, no problem.
I will try and keep this part short. I feel at this time we are over scanning way to much and nothing is being done about it and I am very frustrated and do not know what to do.Basically a good part of our exams are ordered with and without and delays are routine on all abd/pel CT's. I have been able to change some orders when doing so, just to a with only, but I feel that is not doing enough. The first thing I wonder is," why arent the radiologist calling and complaing to us or they should be calling the ordering dr's on why the exams are being ordered that way?" If I was back at my old job we would have been called on the carpet for that. Here it is a different story. It's like they don't care or want to step up and say and do whats right. It just blows me away that a physician(radiologist) who reads these exams,aware of radiation and what it can do lets this go. Maybe I am wrong and scanning some with and without is acceptable and the without phase and delays are benefcial. If thats the case I can live with that and go on . Example, I called a radiologist about scanning someone with and without and I felt it only needed to be done one way and I suggested that when I called. They agreed with me, but then they asked who ordered it and they said just do it with and without because the ordering physician would through a fit. Or if it was ordered that way they would just say "do as ordered".So basically somone was scanned one to many times for the sake of an ordering Dr not throwing a fit.

It's like they don't want to be bothered with it, or I hope not, but for financial benefits for reading and billing for a with and without study. I have approached my supervisors and they do feel the same, but it's like the pink elephant in the room. Everybody knows it's there but does nothing about it. I am dumbfounded by this!

If I am wrong on this principle I would like to know. I know there is no law on saying how someone should be scanned. But it seems like to me any radiologist with a conscious would know better morally,ethically. I am hoping some governing body will step up and start looking at doses more and putting the clamps on the physicians being more responsible. .As we all know there is alot more talk on radiation in the general public concerning CT scans. Yes they are benefical and a great and valuable diagnostic tool, but it needs to be used in a more responsible manner with clinical corralation and evaluation of the patient.

Is it wrong to scan someone with and without and delays? I know
there are exceptions, but this situation weighs heavy on my mind and the radiologist that I work for seem to not even bother if someone is scanned that way. A lot of politics involved,radiologist having different opinions among themselves in the group, not caring and sometimes Dr's can be very difficult to deal with, sorry no offense. I just feel strongly about this issue and I want to know what is right. I was trained a ceratin way for many years and now it's the opposite and does not seem right.

 

[fantasty]

IV contrast increases the radiodensity of structures with a high amount of blood flow. In other words, because IV contrast goes into your blood vessels, tissues that either ARE blood vessels or are highly invested with them will be brighter than they are without contrast and also brighter than surrounding, relatively non-vascular tissue.

Since the technology of CTs and x-rays depends on visualizing the body by creating interfaces between structures of different densities, contrast CTs can both create interfaces and obliterate them. Thus, your indications and contraindications to CT with contrast studies depend on what tissues you are imaging and what you are trying to find.

In pancreatitis, for example, the normally vascular pancreas will "light up" on CT with contrast, but dead areas will not. This allows you to estimate degree of necrosis involved in an acute pancreatitis.

You can also image intraabdominal bleeds because the IV contrast will spill out of lacerations into the abdominal cavity, you can use the interfaces between dense and lucent created by contrast to image hyper- or hypovascular lesions (such as malignancies, which can be either, or abscesses, which are lucent), or you can use contrast studies to search for intravascular filling defects such as when searching for pulmonary embolism or trying to image an aortic dissection.

Hope that helps.

Bump. I was going to PM you anyhow. But, google - 3rd selection was you answering part of my question

 

[fantasty]

Copy and Pasted from my previous response to this same question:
....
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.
...

Well, I give zwei all the credit but thanks

 

[Zweihander]

Bump. I was going to PM you anyhow. But, google - 3rd selection was you answering part of my question

Holy crap I wrote this eleven years ago!!