Scheduler CT/MR Screening Guidelines for Patients with Allergy


Purpose: reduce the number of patients with known allergies scanned at East Clinic, Digestive Health Center, and other non-hospital outpatient centers.

  1. If a patient is being scheduled for a contrast-enhanced CT and has an allergy to iodinated contrast or “contrast” then the study should be done at CSC, TAC or One South Park.
  2. If a patient is being scheduled for a contrast-enhanced MRI and has an allergy to gadolinium-based contrast or “contrast” then the study should be done at CSC, TAC or One South Park.
  3. If the patient has a list of 5 or more allergies to anything and has an order for a contrast-enhanced CT or contrast-enhanced MRI, then the patient should be scheduled at CSC, TAC or One South Park.
  4. If the caller tells the screener that they have had an “anaphylactic” or “anaphylactoid” reaction, and the patient has an order for a contrast-enhanced CT or contrast-enhanced MRI they should be scheduled at CSC or TAC. Please note that the schedulers are not obligated to search the medical records for the severity of reactions.
  5. Pre-medication is only indicated for those patients with known allergies to iodinated contrast or gadolinium-based contrast agents, and should be communicated at the physician level. (See Prophylaxis policy for patients allergic to IV contrast).

Prophylaxis Policy for Patients Allergic to IV Contrast


  1. Ascertain the specific details of the prior reaction.  Determine:
    1. If the patient had a true reaction to intravascular contrast material
    2. Type of contrast used (if available)
    3. Type of reaction and severity
    4. Treatment and its result
    5. Level of patient anxiety
  2. In addition to intravascular contrast administration, the following scenarios should be considered in patients with contrast allergy:
    1. Administration of oral contrast.  1-2% of oral contrast could be absorbed.  So for someone who has a severe contrast allergy, they should get dilute barium as an oral contrast agent.  If prior mild reaction and minimum risk of perforation/leak, no need to premedicate.  For moderate reactions or risk of peritoneal leak, consider premedication or dilute barium alternate oral contrast.
    2. Arthrograms.  Because allergic-like reactions are dose-independent, and arthrograms use a needle and cross the bloodstream, use the same premedication strategy for arthrograms that is used for intravenous media. For patients with known contrast allergies, appropriate to premedicate or switch to US if possible.
    3. Hysterosalpingograms: In patients with patent fallopian tubes, there is peritoneal spill of contrast.  Intraperitoneal contrast is absorbed (intraperitoneal=intravascular).  Because of the dose independence, premedication for HSGs should be performed in patients with known contrast allergies.
  3. Determine if an examination without contrast can provide adequate diagnostic information.
  4. If still convinced of the need for intravascular contrast, the service requesting  the scan should:
    1. Contact the radiologist scheduled on service for the proposed date of the study (GI/GU, CT, Angiography, Neuroradiology, or on-call resident for overnight/weekend Emergency Department patients).  If the staffing schedule is not available for the proposed date of the examination, then the Chief of the GI/GU Service (Dr. Perry Pickhardt), CT Service (Dr. Meghan Lubner), Angiography/Interventional Service (Dr. Orhan Ozkan), or Neuroradiology Service (consultant for the day) should be contracted.
    2. Discuss why an alternative imaging method will not suffice
    3. If the risk is determined to be acceptable; schedule the contrast examination and transmit prophylaxis instructions.
  5. Routine Contrast Reaction Prophylaxis (12 hour):
    1. Methylprednisolone (Medrol)
      1.  32 mg by mouth at 12 and 2 hours before contrast injection.
    2. Diphenhydramine (Benadryl):
      1. 50 mg intramuscular or oral 1 hour before contrast injectionOR
      2. 50 mg (or 25 mg per height/weight indication) intravenously 15-20 min before contrast injection
        Note:  The Benadryl must be used with the proviso that the patient does not drive a car or operate heavy machinery 4-6 hours after the Benadryl is administered.
        NEJM 1987; 317: 845-849.
    3. If a patient is unable to take oral medication, consider the 5 hr regimen detailed in #6.  Alternatively the methylprednisolone may be substituted with 200 mg hydrocortisone IV at 13, 7, and 1 hour before contrast administration. If a patient is allergic to diphenhydramine in a situation where diphenhydramine would otherwise be considered, an alternate anti-histamine without cross-reactivity may be considered, or the anti-histamine portion of the regimen may be dropped.
  6. Rapid Contrast Reaction Prophylaxis (5 hours):
    1. To be used only in a truly urgent situation after discussion between the requesting service and the appropriate radiology service.
    2. The requesting service must place a note in HealthLink outlining the necessity of contrast-enhanced examination and the rapid prohpylaxis protocol.
    3. Hydrocortisone:
      1. 200 mg intravenously 5 and 1 hour before contrast injection
    4. Diphenhydramine (Benadryl):
      1. 50 mg intravenously 1 hour before contrast injection

Greenberger PA et al. Emergency administration of radiocontrast media in high-risk patients. J Allergy CLin Immunol. 1986; 77(4): 630-634.

Mervak BM, Cohan RH, Ellis JH, Khalatbari S, Davenport MS.  Premedication administered 5 hours before CT compared with a Traditional 13-hour Oral regimen.  Radiology 2017; 285(2), 425-433..

Metformin-Containing Medications

List of diabetic medications known to contain Metformin

  • ActoPlus Met®
  • ActoPlus Met XR®
  • Avandamet®
  • Fortamet®
  • Glucophage®
  • Glucophage XR®
  • Glucovance®
  • Glumetza®
  • Invokamet®
  • Janumet®
    Janumet XR®
  • Jentadueto®
  • Kazano®
  • Kombiglyze XR®
  • Metaglip®
  • PrandiMet®
  • Riomet®
  • Xigduo XR

Conditions Limiting the Use of IV Contrast

Conditions Which May Contraindicate The Use Of IV Iodinated Contrast


Non-ionic IV contrast may be safely administered in these patients based on Bessell-Browne et al, CT of Pheochromocytoma and Paraganglioma: Risk of adverse events with IV administration of non-ionic contrast material, AJR 2007; 188: 970-974 and the ACR manual. No follow-up blood pressure monitoring is needed. Direct injection of contrast medium into the adrenal or renal artery is to be avoided however, as this may cause a hypertensive crisis.


Patients with allergies have twice the risk of contrast reactions compared to the average patient.


Patients with asthma have five times the risk of contrast reactions compared to the average patient.

IL-2 (Interleukin – 2 Chemotherapy)

Patients who are currently on IL-2, or have received IL-2 in the recent past, have an increased risk of delayed reaction. The reaction can occur up to several hours after the injection, and can be mild to severe. Symptoms can include hives, rash, pruritis, fever, chills, joint pain, flu-like symptoms, tachycardia, or hypotension. Symptoms can be mild and self-limited, or severe requiring hospitalization. Patients who have experienced an IV contrast reaction while on IL-2, or after IL-2 therapy should not receive IV contrast for any future imaging unless an extreme situation arises. (IL-2 patients should NOT receive steroid pre-medication. That counteracts the intended effect of IL-2).

Patients receiving IV contrast who are currently on IL-2 therapy or for 6 months following the completion of IL-2 therapy must be monitored for a minimum of two hours after their CT scan. This is usually done in the oncology clinic or in our waiting room after the scan. Six months after the cessation of therapy or after 2 uneventful contrast-enhanced scans the patient may return to normal monitoring.

Diabetes, Renal Failure, Nephrectomy, Renal Transplant

Please see the IV contrast agent guidelines.


Metformin is an oral antihyperglycemic medication administered alone or in combination (see a list of metformin containing medications). There have been case reports of patients developing lactic acidosis after receiving iodinated contrast material while on metformin. Therefore, if a patient is on metformin, or a metformin containing medication, determine which of the two following categories describes the patient’s situation:

  1. No evidence of acute kidney injury and an eGFR ≥ 30.  In this setting, metformin can be continued and there is no need to reassess renal function.
  2. Acute kidney injury or severe chronic kidney disease (stage IV or stave V, eGFR <30) OR arterial catheter studies that might result in emboli to the renal arteries. In this setting, metformin should be held 48 hours after the contrast bolus/procedure. Renal function should be reassessed 48 hours after the contrast load; if renal function is normal (or at baseline), metformin may be restarted.

Active Gout

A disease that causes hyperuricemia. The patient needs to have a normal creatinine level and not be dehydrated prior to receiving IV contrast, to reduce the risk of acute renal failure. (note: patients with only a history of gout but not active are not considered at risk)

Multiple Myeloma

A malignant bone condition that causes kidney failure, dysproteinemia, abnormal proteins in the plasma, and abnormal urine proteins (Bence Jones proteins). IV contrast may cause the proteins to precipitate resulting in renal tubular obstruction and possibly renal failure. Multiple myeloma is only considered a risk factor for contrast nephrotoxicity when combined with pre-existing renal insufficiency.

Creatinine level must be known prior to IV contrast administration. Please reinforce the importance of hydration after contrast administration.

Who must have a creatinine level prior to IV contrast?


reference: Manual on Contrast Media Version 9.0, ACR

All inpatients require a current (within one week) creatinine level or estimated glomerular filtration rate (eGFR) prior to an IV contrast-enhanced CT.

Outpatients being scheduled for a CT with IV contrast will not require a serum creatinine unless they meet one of the following criteria:

  1. Over 60 years old.
  2. Diabetic treated with insulin or other provider-prescribed medications (e.g., metformin).
  3. Receiving chemotherapy or an aminoglycoside within the last 1 month.
  4. Diagnosis of a collagen vascular disease.
  5. Diagnosis of a paraproteinemia syndrome or disease (e.g., multiple myeloma).
  6. History of “chronic kidney disease” including tumor, surgery, single kidney, or kidney transplantation.
  7. History of end-stage liver disease.
  8. History of severe congestive heart failure.

For outpatients, a measure of renal function is considered current if it has been obtained within one month.

All adult ED patients should have a same day Cr, with the exception of trauma or extremely stat situations. These parameters are intended to serve as guidelines. Obviously, medical necessity may mandate administering contrast without a current measure of renal function.