CT with or without contrast?

[rhiannon777]

I'm writing up an H&P for a patient who presented to the ED with lower abdominal pain of several weeks duration. My differential includes abscess, malignancy, and diverticulitis. I realized I have no idea when to use contrast for abdominal/pelvic CT. What's the guideline?

---

Members don't see this ad.

 

[jdh71]

I'm writing up an H&P for a patient who presented to the ED with lower abdominal pain of several weeks duration. My differential includes abscess, malignancy, and diverticulitis. I realized I have no idea when to use contrast for abdominal/pelvic CT. What's the guideline?

contrast will allow you to see things better in the abdomen, but it can be hard on the kidney, and most of the time you can't get one with contrast if the creat is over 1.5-1.6 . . . so generally those with acute renal failure or those with chronic renal disease can't get the contrast

basically, if you can use it, you want to

 

[NYRN]

Agree with all above. Radiology will give you a hard time if creatinine borderline. In my hospital, it has to be an attending to attending discussion on the risk vs. benefit to give IV contrast in that case.

Anyway, I just want you to remember to ask the patient about any iodine or shellfish allergy. Ask about specific food such as shrimp, crab, etc. Believe it or not, people do not know what constitues "shellfish". Better to be safe than sorry.

If scanning for renal calculi, you do not need to use IV contrast or PO contrast. Head CT for the stroke protocol does not use IV contrast either in all cases.

 

[jdh71]

Anyway, I just want you to remember to ask the patient about any iodine or shellfish allergy. Ask about specific food such as shrimp, crab, etc. Believe it or not, people do not know what constitues "shellfish". Better to be safe than sorry.

shellfish = iodine allergy is actually, apparently, bull**** . . . dogma being what it is . . .

If scanning for renal calculi, you do not need to use IV contrast or PO contrast. Head CT for the stroke protocol does not use IV contrast either in all cases.

 

[NYRN]

If it really is BS, you very well could be right. Honestly I have no idea. In my experiences, MD's have covered their butts and don't order IV contrast on anyone who claims shellfish allergy, so the only people I have seen with a reaction didn't have this history.

 

[Smurfette]

gold standard for a CT abd/pelvis is po and IV contrast. The po contrast helps show bowel (especially in post op patients or patients you are worried about abscesses, as a plain CT can be hard to differentiate bowel from abscess). IV contrast is optimal (shows much better definition of planes, in addition to lighting up the vessels, liver, spleen, kidneys and ureters/bladder). If you are worried about malignancy the IV contrast will help light up the liver to show mets.

As mentioned above, renal stone protocol is without contrast....usually a CT with po and iv is done by scanning the patient 3 times: 1. initial 'plain' scan (shows po contrast), 2. with IV infusion, and 3. 5 minute delay after contrast infusion (shows contrast excretion into bladder).

 

[rhiannon777]

Thanks! This is really helpful.

Out of curiosity, does a CT with and without essentially double the cost above what a CT with would be?

 

[IM Substance P]

Thanks! This is really helpful.

Out of curiosity, does a CT with and without essentially double the cost above what a CT with would be?

Yes, if you're referring to radiation to the patient. The patient gets twice the radiation.

If you're referring to the patient's bill (which I'm sure you are), the cost difference isn't as bad as you'd think. It's probably around $1500-$2000 for any abdominal CT, regardless of contrast.

The value of a double-contrast CT (oral and IV) for an abdominal complaint is much higher than the value of a non-contrast CT.

That said, you should be using abdominal CT sparingly. Unfortunately, it's very overutilized in the ED, so most patients get them anyways.

 

[Rendar5]

If it really is BS, you very well could be right. Honestly I have no idea. In my experiences, MD's have covered their butts and don't order IV contrast on anyone who claims shellfish allergy, so the only people I have seen with a reaction didn't have this history.

It's all complete BS. People have contrast allergies or not. People do not have iodine allergies. If you did, you would have an allergic reaction everytime you had table salt which is usually iodinated in this country. Not to mention what a shellfish allergy has to do with iodine to begin with.............. Doesn't even come close to passing a sniff test (doesn't smell right).

 

[NYRN]

It's all complete BS. People have contrast allergies or not. People do not have iodine allergies. If you did, you would have an allergic reaction everytime you had table salt which is usually iodinated in this country. Not to mention what a shellfish allergy has to do with iodine to begin with.............. Doesn't even come close to passing a sniff test (doesn't smell right).

That's good to know. I honestly had no idea if they would really have an allergic reaction to contrast if they claimed an iodine allergy. Maybe people have sued if they coincidentally had an allergic reaction to contrast while claiming an iodine allergy? It's all CYA these days so I guess its up to the individual provider if they order contrast regardless of "allergy"?

 

[jdh71]

In my experience most of the "iodine/shellfish" allergy people are merely drug seekers, making sure you have no good way of ruling out serious pathology.

 

[mules05]

Remember there is more than one way to give contrast. If you're looking for an abscess or gut pathology (appendicitis, diverticulitis, perforated bowel) you need to give PO contrast. Anyone with abdominal pain should get PO contrast- it doesn't have a substantial effect on the kidneys, and patients who list an allergy to contrast almost universally have an allergy to IV contrast.

IV contrast is useful when evaluating abdominal vessels, or anytime you're getting a CT of the chest. Really, the only time a non-contrast CT is at all useful is evaluating bones (the spine in particular) or head.

 

[Law2Doc]

In my experience most of the "iodine/shellfish" allergy people are merely drug seekers, making sure you have no good way of ruling out serious pathology.

In which case they will also claim to be "allergic" to NSAIDS, and will probably ask for a narcotic by name (and even dosage).

 

[Law2Doc]

shellfish = iodine allergy is actually, apparently, bull**** . . . dogma being what it is . . .

Yeah, this was debunked a few years back. Still taking time to get the word out.

 

[MattD]

In which case they will also claim to be "allergic" to NSAIDS, and will probably ask for a narcotic by name (and even dosage).

http://www.youtube.com/watch?v=jCxpro-QSio

http://www.youtube.com/watch?v=_m64cy1MMPg

 

[NYRN]

In which case they will also claim to be "allergic" to NSAIDS, and will probably ask for a narcotic by name (and even dosage).

Of course! They are allergic to Tylenol but they want Percocet or Vicodin. Only Demerol or Dilaudid works for them!

 

[CATrtb]

There are several ways to order an A/P CT depending on what you are looking for.

CT A/P w/IV and w/PO= the standard for the vast majority of things, generalized abd pain, abcess, diverticulitis, tumors, SBO, appendicitis, hernias, etc., etc...

CT A/P w/IV and NO PO= trauma

CT A/P w/o/w IV and w/PO= CA workups or followups--may need to add "multiphase imaging" (w/o, arterial phase, portal venous phase, delayed phase) for particular tumors

CT A/P w/o/w IV and NO PO= some urology protocols

CT A/P w/o IV and w/PO= creatinine high, allergic to IV contrast (although you can do a steriod/benedryl prep in some cases)

CT A/P w/o IV and w/o PO= renal stones

CTA Abd w/o/w IV=(CT angiography) w/o/w IV contrast is the only way to order this. NO PO for CTA. Shows abd aorta and its branches (dissection, AAA, stenosis, eval stents, etc). Make sure the patient has a 20G or larger IV in the AC or above. If you want the illiacs and lower then go ahead and order the CTA Pelvis w/o/w.

 

[Rendar5]

An important note, whether or not you include PO contrast for Appy's is very institution dependent. Some institutions will refuse to do CTs and may only do ultrasounds (you need very experienced ultrasounders to use it for appy's. Usually you'd need a radiologist and not a tech because it's very hard to spot a normal appendix and you'd get an equivocal result of "no appendicitis seen, appendix not visualized". My institution will allow a non-PO contrast CT to be done to r/o appendicitis in all non-skinny males since stranding, around the appendix is a good sign in guys, but they dont' trsut themselves to do it on women without PO contrast.