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CT scans and MRI scans are high tech imaging studies that give doctors the ability to look at the internal anatomy of the body in great detail. One of the tools used to help in differentiating normal structures from abnormal structures like tumors, aneurysms, infection, is IV contrast dye. The dye used in CT scans is based on low osmolar contrast material and for MRI scans on gadolinium. The dye is injected through an IV catheter placed in a vein (usually in the arm or hand). The contrast highlights different tissue types bringing out vessels, tumors, inflammation, cysts, etc, that might be missed if the dye was not administered for the scan.

Many patients are unaware of the side effects of the dye or misinformed (and uninformed) about the risk of contrast administration. A recent contrast injection study by the Mayo Clinic in Rochester, MN looked back at over 450,000 dye injections. Below is a brief summary of their experience:

• CT scan dye side effects were 0.15%
  
• MRI dye side effects were 0.04%
  
• Most common side effects were hives and nausea
• 19 patients had a severe side effect (requiring medication, treatment)
• 1 patient died which is a mortality risk of 0.0003%

Clearly there is a risk of a severe reaction to the dye or even death. However, as the Mayo Clinic reports the vast majority of their patients did not have a reaction.

Although reactions to contrast are rare, it is standard practice to inform you of the possibility of dye administration and its potential side effects. However, keep in mind that many imaging facilities will not have a verbal discussion with you regarding IV contrast administration. It's usually in the paperwork you fill out before the test. Make sure you read and understand what you are signing in advance!

Have you had a contrast dye injection? What was your experience like? Leave your comments below.

Many CT scan tests require injection of IV contrast (dye). IV stands for intravenous which means the contrast is given through a vein. Generally a vein in your hand, lower arm, or near the elbow joint is used. The contrast is used to "highlight" internal organs such as the liver, kidneys, and pancreas. It helps detect and characterize tumors, infection and disease of the vessels.

Contrast scans are ordered either "with only", meaning contrast is given and then the images are taken or "with and without", which means images are taken before the contrast is administered and then immediately during or after the contrast is injected.

Into the scan room

Once you're in the CT scan room you'll be taken to a table and asked to lie down. The CT technologist may take a few images in preparation for the scan and/or do the "non-contrast" part of the scan first. That is, take images that are needed before the IV contrast injection is done.

The IV tray

Most facilities will have the IV materials on a metal tray near the CT scan machine. This will include a tourniquet, alcohol pad, IV catheter, gauze, tape, syringe with saline, and some tubing to connect to the injector (the part of the machine that injects the IV contrast - it looks like a big ray gun).

Getting the IV

Unlike a blood draw, the IV catheters used are larger and will need to stay in a vein. Larger IVs are used as the contrast is injected at a high rate. You'll be asked to straighten your arm and hand. The technologist will place the tourniquet around your upper arm or wrist.

The technologist will check for a vein, sometimes using a tapping or brushing movement across your arm. After finding a suitable vein, the technologist will clean the area with an alcohol pad and position the IV over the vein. The IV is advanced through the skin and into the vein. This might take a few tries, particulary for patients who may be dehyrated, have had multiple injections, or chemotherapy.

Once the IV is placed, a small amount of saline is sometimes injected to test it. The IV is then hooked via tubing to the injector. The table will move and the technologist will leave the room to begin the injection and scan.

The injection

The contrast will flow from the injector, through the tubing and into the IV and then the vein. You may feel a "pop" in the beginning of the injection right at the IV site. As the contrast goes into the vein you will feel the fluid rush up your arm. You shouldn't feel any pain - if you do alert the technologist immediately.

After a few seconds the contrast reaches your chest and heart and you'll feel an intense warm feeling. Some have described it as a "sunburst" or like drinking a hot cup of coffee in one gulp. You might also get a metallic taste in your mouth.

Usually the scanner begins taking pictures within 10-20 seconds after the injection begins and continues to take pictures after the injection is completed.

After the injection

The technologist will remove the IV and place a small piece of gauze with tape over the IV site. 

What about side effects?

The most common side effect of contrast is a mild allergic reaction - sneezing, coughing, asthma-like symptoms and small hives. Severe allergic reactions can lead to heart and lung failure. Contrast can also damage the kidneys. If the contrast leaks from the IV and into the tissues of the hand or arm, it can cause pain and inflammation.

These are just some of the side effects of contrast. Your local Radiology center or hospital can give you more detailed information about the risks and benefits of IV contrast.

And remember, if you've had a side effect to contrast in the past, make sure you alert the Radiology facility and your doctor in advance.

An CT scan is high-tech medical imaging test that can help your doctor diagnose many different types of disease.  You can read more about CT scans here. (For MRI and contrast click here.)

When your doctor decides to send you for a CT scan he or she will fill out a prescription or a Radiology referral form. The form will usually have your name, your symptoms, the doctor's signature, and the type of test being ordered.

The CT scan your doctor orders usually matches the body part where you are having symptoms. For example, if you have pain in your stomach, your doctor will order a CT scan of the abdomen. Many CT scans are ordered with contrast (aka dye). If your doctor orders it without contrast, on occassion the Radiologist interpreting the scan may recommend that the test be done with contrast. 

CT Scan Contrast Indications

Many CT scans are ordered with contrast.  Here are some common reasons why contrast is given:

• History of tumor, cancer, or surgery
• Looking for infection, inflammation, or cancer
  
• Evaluating blood vessels
  
• Investigate a finding in a scan done without contrast

CT Scan Contrast Side Effects

There are risks associated with the injection. The most common side effects include:

• Mild to life-threatening allergic reaction
• Flushing/redness and hives
  
• Shortness of breath
• Nausea, vomitting
  
• Blood clots
• Dizziness

Some people develop allergies to CT scan dye over time. For example, a patient may have no side effects with multiple contrast CT scans but then experience one. Because the risk of severe life-threatening reaction increases, if these patients need another CT scan with contrast they are pre-medicated with Benadryl and steriods to reduce the risk or severity of another reaction.

If you've had a reaction to CT scan or IVP dye in the past you should inform your doctor and the Radiology staff.

The Contrast Injection

You might have some non-contrast images taken before the contrast is administered. The techologist will then come into the CT scan room and back the table out of the tube. The technologist or the Radiologist will then place a tourniquet around your arm or hand and insert an IV and connect it to plastic tubing. The tubing is connected to an injector. The IV will remain in your vein for the rest of the test. You'll be asked to place your arms above your head. The technologist will leave the room. The scanner will start and the injection will begin. You'll feel a warm rush of fluid into your arm, chest and abdomen. Some people describe the feeling as "rushing heat" or a "sun burst". After the test, the IV is removed.

Passing on the Contrast Injection

As a patient, you have the right to be informed and decide how you receive medical treatment. If you are afraid of the injection or potential contrast side effects, you should discuss this with your doctor or the Radiologist at the facility and learn more about why the contrast is being given.