IV Contrast – mostly safe but sometimes …

12th October 2026, NIA Diagnostic Imaging

IV contrast

Contrast media play a significant role in modern medical imaging, as it helps radiologists and other healthcare professionals visualise blood vessels, organs, soft tissue, and abnormalities more clearly. It also helps in detecting lesions, assessing vascularity, and guiding treatment planning. Contrast media is generally given during specific scans such as CT, MRI, angiography, fluoroscopy, and even ultrasound.

Although contrast media are generally very safe, some patients may experience an anaphylactic reaction – similar to any other allergic reaction! Another possible complication is contrast extravasation, where contrast leaks from the vein into the surrounding tissues during injection.

Most patients receive contrast without any complications. Anaphylactic-type reactions are rare, accounting for 0.6% of cases, with only 0.04% considered aggressive (1). Almost all life-threatening contrast reactions occur within the first 20 minutes of intravenous injection (2). However, all imaging departments have protocols and emergency equipment available to manage any issues that may occur.

What is IV Contrast media?

IV contrast media are substances that temporarily change the way X-rays or other imaging tools interact with the body (3). It is a clear liquid that is injected into a vein to help with visualisation of anatomy during the scan. It does not change any internal organs and is naturally excreted by the body via urine or bowel movements. However, patients with significant kidney impairments may require additional assessment before administration of any IV contrast to ensure patient safety.

Different types of IV contrast can be administered depending on the examination:

Iodinated Contrast – CT

Iodinated contrast is most commonly used for contrast-enhanced CT examinations and CT angiography.

Figure 1. CT abdomen scan – with or without contrast

It contains iodine, which absorbs X-rays and makes blood vessels and certain organs appear more clearly on CT images. Modern iodinated contrast agents are generally non-ionic and low osmolar, which is associated with fewer adverse reactions.

2. Gadolinium-based Contrast – MRI

Gadolinium-based contrast agents (GBCAs) are used during some MRI examinations to improve visualisation of tissues, blood vessels, and areas of abnormal enhancement.

Figure 2. MRI Brain scan with or without contrast

Gadolinium contrast is chemically different from iodinated contrast and is used specifically because of its properties in the MRI environment.

When IV contrast is administered, normal symptoms and sensations patients may feel include (3):

Brief warm or flushing sensation
Metallic taste
Sensation of needing to urinate
Mild nausea

These sensations usually resolve quickly and do not necessarily indicate an allergic reaction. These symptoms should be temporary and are experienced immediately after contrast is injected.

IV Contrast Reactions

Contrast reactions can range from mild symptoms to potentially life-threatening emergencies. Each reaction is categorised by severity and clinical features (4) (5) to guide management protocols.

1. Mild Reactions

Symptoms and signs include:

Nausea
Mild vomiting
Transient flushing or warmth
Mild itching
Limited urticaria (hives)
Persistent coughing

Management includes:

Terminating contrast administration
Assessment of the patient
Observing progression of symptoms
Escalating event if symptoms worsen

2. Moderate Reactions

Symptoms and signs include:

More extensive urticaria
Facial or periorbital swelling
Persistent vomiting
Wheezing or bronchospasm
Significant changes in blood pressure

Management includes:

Monitoring oxygen saturation and vital signs
Providing oxygen where clinically indicated
Medical review
Administration of medications according to the department’s emergency protocol
Continued observation

3. Severe Reactions

Symptoms and signs include:

Anaphylaxis
Severe bronchospasm
Significant airway swelling
Laryngeal oedema
Severe hypotension
Altered consciousness
Cardiorespiratory arrest

Management includes:

Calling for emergency assistance
Maintaining airway and breathing
Oxygen and respiratory support as clinically indicated
Establishing or maintaining IV access
Administration of emergency medications according to protocol
Continuous monitoring
CPR if required

4. Delayed Reactions

Not all reactions occur during the scan. Some hypersensitivity reactions may develop hours to

several days after contrast administration.

Possible symptoms include:

A new skin rash
Itching
Redness or scattered raised lesions

Patients should contact a healthcare professional if a new or persistent rash/symptom develops after contrast administration.

Seek emergency medical assistance if there is difficulty breathing, swelling of the tongue or throat, fainting, or a widespread rash associated with blistering, skin peeling or sores affecting the mouth or eyes.

Before receiving contrast, patients should tell healthcare professionals if they have previously experienced a reaction to contrast. The imaging team can assess the previous reaction and determine the safest approach for future examinations. Depending on the circumstances, this may involve using a different contrast agent, taking additional precautions, choosing alternative imaging, or using other measures.

What is Contrast Extravasation?

Contrast extravasation occurs when IV contrast leaks out of the vein and into the surrounding soft tissues during injection. However, contrast extravasation and contrast reactions are two different reactions.

Contrast reaction is a systemic response to the contrast agent while an extravasation is contrast leaking outside the vein during the injection. Contrast extravasation can occur due to fragile or small veins, difficult venous access, cannula position, high injection pressure and flow rate.

Patients may notice common symptoms around the injection site, such as (6):

Swelling
Tightness or pressure
Pain
Redness
Discomfort around the cannula
Skin discolouration

Majority of extravasations are managed conservatively and resolve without long-term problems, but rare severe injuries can occur and should be promptly managed. Most extravasations are minor, but urgent assessment is important if there are signs suggesting a more significant injury.

Seek urgent medical review if there is (6) (7):

Severe or increasing pain
Significant or rapidly increasing swelling
Blistering
Skin ulceration
Marked skin discolouration
Numbness or altered sensation
Reduced circulation
Symptoms continue to worsen

What happens after a Contrast Reaction or Extravasation?

Following an event, the healthcare team may:

Continue monitoring the patient
Provide appropriate medical attention
Give instructions for monitoring the affected area
Recommend that patients tell healthcare professionals about the event before future contrast examinations

Ultimately, while IV contrast is generally safe, understanding potential complications, including contrast reactions and extravasation, is essential for both patients and healthcare professionals. Contrast enhanced imaging provides important diagnostic information that helps guide treatment and ongoing patient care.

References

1. Bell, D., & Di Muzio, B. (2016). Iodinated contrast media adverse reactions. Radiopaedia.Org. https://doi.org/10.53347/rid-42772. https://radiopaedia.org/articles/contrast-media-adverse reactions

2. American College of Radiology. (2024). ACR manual on contrast media. Acr.Org. https://www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Contrast-Manual. https://www.acr.org/clinical-resources/clinical-tools-and-reference/contrast-manual

3. Radiological Society of North America (RSNA) and American College of Radiology (ACR). (2018). Contrast Materials. Radiologyinfo.Org. https://www.radiologyinfo.org/en/info/safety-contrast. https://www.radiologyinfo.org/en/info/safety-contrast

4. ASCIA Radiocontrast Media Hypersensitivity – Australasian Society of Clinical Immunology and Allergy (ASCIA). (n.d.). Www.Allergy.Org.Au. https://www.allergy.org.au/hp/drug-allergy/radiocontrast-media

5. Bell, D., & Di Muzio, B. (2016). Iodinated contrast media adverse reactions. Radiopaedia.Org. https://doi.org/10.53347/rid-42772. https://radiopaedia.org/articles/contrast-media-adverse-reactions

6. Radswiki. (n.d.). Contrast media extravasation | Radiology Reference Article | adiopaedia.org. Radiopaedia. https://radiopaedia.org/articles/contrast-media-extravasation.

7. Belzunegui, T., Jean Louis, C., Torrededia, L., & Oteiza, J. (2011). Extravasation of radiographic contrast material and compartment syndrome in the hand: a case report. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, 19(1), 9. https://doi.org/10.1186/1757-7241-19

9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3044092/

Figure 1: Hartung, M. P., Cadogan, M., & Cadogan, M. P. H. M. (2023, February 1). Abdominal CT: Basics. Life in the Fast Lane • LITFL. https://litfl.com/abdominal-ct-basics/ https://litfl.com/abdominal-ct-basics/

Figure 2: Naim, I. (2025, May 22). A Patient’s Guide To MRI Contrast | All You Need To Know – MRI Lucknow. MRI Lucknow. https://mrilucknow.net/mri-contrast/ https://mrilucknow.net/mri-contrast/

PFO Closure

Furlan AJ, Reisman M, Massaro J, et al. Closure or medical therapy for cryptogenic stroke with patent foramen ovale. N Engl J Med 2012; 366: 991–

A multicenter, randomized, open-label trial of closure with a percutaneous device, as compared with medical therapy alone, in patients between 18 and 60 years of age who presented with a cryptogenic stroke or transient ischemic attack (TIA) and had a patent foramen ovale. The primary end point was a composite of stroke or transient ischemic attack during 2 years of follow-up, death from any cause during the first 30 days, or death from neurologic causes between 31 days and 2 years.

Results:

Primary end point was 5.5% in the closure group as compared with 6.8% in the medical-therapy group (adjusted hazard ratio, 0.78; 95% confidence interval, 0.45 to 1.35; P = 0.37)

Conclusion:

“In patients with cryptogenic stroke or TIA who had a patent foramen ovale, closure

with a device did not offer a greater benefit than medical therapy alone for the

prevention of recurrent stroke or TIA”

2 Saver JL, Carroll JD, Thaler DE, et al. Long-term outcomes of patent foramen ovale closure or medical therapy after stroke. N Engl J Med 2017; 377: 1022–

A multicenter, randomised, open-label trial ,randomly assigned patients 18 to 60 years of age who had a patent foramen ovale (PFO) and had had a cryptogenic ischemic stroke to undergo closure of the PFO (PFO closure group) or to receive medical therapy alone (aspirin, warfarin, clopidogrel, or aspirin combined with extended-release dipyridamole; medical-therapy group). The primary efficacy end point was a composite of recurrent nonfatal ischemic stroke, fatal ischemic stroke, or early death after randomisation.

Results:

Recurrent ischemic stroke occurred in 18 patients in the PFO closure group and in 28 patients in the medical-therapy group, resulting in rates of 0.58 events per 100 patient-years and 1.07 events per 100 patient years, respectively (hazard ratio 0.55; 0.31 – 0.999; P = 0.046)

Conclusion:

“Among adults who had had a cryptogenic ischemic stroke, closure of a PFO was associated with a lower rate of recurrent ischemic strokes than medical therapy alone during extended follow-up.”

Meier B, Kalesan B, Mattle HP, et al. Percutaneous closure of patent foramen ovale in cryptogenic embolism. N Engl J Med 2013; 368: 1083–

A prospective, multicenter, randomised, event-driven trial, randomly assigned patients to medical therapy alone (anti-platelet or warfarin therapy) or closure of the patent foramen ovale.

Results:

9 patients in the closure group and 16 in the medical-therapy group had a recurrence of stroke (hazard ratio with closure, 0.49; 0.22 – 1.11; P = 0.08). The primary analysis of the intentionto- treat cohort showed a nominal 51% hazard rate reduction with closure, but the reduction did not reach significance.

Conclusions:

” …there was no significant benefit associated with closure of a patent foramen ovale in adults who had had a cryptogenic ischaemic stroke.”

Sondergaard L, Kasner SE, Rhodes JF, et al. Patent foramen ovale closure or antiplatelet therapy for cryptogenic stroke. N Engl J Med 2017; 377: 1033–

Multinational trial involving patients with a PFO who had had a cryptogenic stroke, randomly assigned patients to undergo PFO closure plus antiplatelet therapy or to receive antiplatelet therapy alone.

Results:

During a median follow-up of 3.2 years, clinical ischemic stroke occurred in 6 of 441 patients (1.4%) in the PFO closure group and in 12 of 223 patients (5.4%) in the antiplatelet-only group (hazard ratio, 0.23; 0.09 to 0.62; P=0.002).

Conclusions:

“Among patients with a PFO who had had a cryptogenic stroke, the risk of subsequent ischemic stroke was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone; however, PFO closure was associated with higher rates of device complications and atrial fibrillation.”

Mas JL, Derumeaux G, Guillon B, et al. Patent foramen ovale closure or anticoagulation vs. antiplatelets after stroke. N Engl J Med 2017; 377: 1011–

In a multicenter, randomised, open-label trial patients 16-60 years of age who had had a recent stroke attributed to PFO, to transcatheter PFO closure plus long-term antiplatelet therapy, antiplatelet therapy alone or oral anticoagulation.

Results:

No stroke occurred among patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet- only group (hazard ratio, 0.03; 0 to 0.26; P<0.001). Large number of patients discontinued anti-coagulation in the anti-coagulant group and statistical significance was not analysed because the study was not adequately powered to compare outcomes.

Conclusion:

“Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation.”

Lee PH, Song J-K, Kim JS, et al. Cryptogenic stroke and high-risk patent foramen ovale: the DEFENSE-PFO Trial. J Am Coll Cardiol 2018; 71: 2335–

Patients with cryptogenic stroke and high-risk PFO were divided between a transcatheter PFO closure and a medication-only group.

Results:

No events occurred in the PFO closure group. 12.9% of patients in the medication group had an event (p= 0.023).

Conclusion:

“PFO closure in patients with high-risk PFO characteristics resulted in a lower rate of the primary endpoint as well as stroke recurrence”