When radiologists need to distinguish organs, tissues or blood vessels in medical images (x-rays, CT scans and MRI), they use contrast.
Contrast doesn’t physically change the color of your tissues or organs, but it makes them appear more clear and easier for a radiologist to see. This allows them to make a more accurate diagnosis and provide the best treatment.
What is Contrast Dye?
Contrast dye is a substance that radiologists use to help them visualize your insides on medical scans like X-rays, CT (computerized tomography) and MRIs more clearly. This doesn’t mean that it physically changes the color of your organs, but it does temporarily change how the insides look on an image, so they appear white on the picture.
There are a variety of contrast agents used in these imaging tests, including iodine-based materials, barium-sulfate, gadolinium, and a saline and air mixture that can be swallowed or injected intravenously. The type of contrast agent you receive is determined by the specific test and what structures your doctor needs to see.
For example, a gadolinium-based contrast agent is often used during an MRI, where it helps radiologist spot tumors that aren’t as visible on a standard X-ray. It also allows your radiologist to spot areas of soft tissue that may be inflamed, which is important for the treatment of certain diseases such as multiple sclerosis (MS).
Other types of contrast are available for other diagnostic imaging tests like ultrasounds and CAT scans, but they don’t have the same benefits. For example, they can cause complications, such as deep vein thrombosis (DVT), which is an abnormal blood clot that can form in your leg or arm.
The best way to prepare for an X-ray, CT scan, or MRI with contrast is to drink lots of water and fluids so that your body can get rid of the contrast before the exam begins. It’s also a good idea to wear comfortable clothing that will allow you to move freely while the dye is being administered.
Depending on your diagnosis, you may need to have a CT scan with contrast to help your doctor better determine your diagnosis or treatment plan. It’s also possible that you’ll need to have a MRI with contrast so your radiologist can spot lesions in your brain or other parts of your body that may be growing and changing.
How is Contrast Dye Used?
Contrast dye is used to make certain parts of your body more visible on images taken with X-rays, CT scans, or MRI. It is also used to help radiologists determine what is going on in your organs and tissues.
Radiologists often need to use contrast dyes in order to obtain clear, detailed pictures of the inside of your body. This can happen when your doctor needs to see blood vessels or other structures, such as a tumor, that are hard to detect without imaging tools.
There are several different kinds of contrast dyes that doctors use during a variety of medical imaging tests. Some of them, like iodine-based contrast and barium-sulfate, are given orally; others, such as gadolinium contrast, are injected intravenously.
Whether you need to take contrast before an X-ray, CT or MRI test depends on your doctor’s judgment and what your condition or illness is. In most cases, the contrast medium is not needed to get good images – but it can make the images look better and help your radiologist develop an accurate diagnosis.
Your radiologist will ask you if you have any kidney problems or other health conditions that could affect how your body excretes the contrast material, such as diabetes or heart or blood diseases. If you have these conditions, your radiologist may recommend getting a blood test before the exam to make sure that your kidneys are working properly.
If your kidneys aren’t working well, the contrast material can break down too quickly, which could lead to a complication called nephrogenic systemic fibrosis. This complication can cause thickening of the skin and connective tissues around your joints, stomach, and lungs.
In some people, the contrast dye can cause a serious kidney complication called congenital contrast-induced nephropathy (CIN). It happens in about 2 percent of patients who receive iodine or gadolinium. CIN is more common in patients with advanced chronic kidney disease and in people who have diabetes or a history of heart or blood problems.
While many hospitals have started using alternative labelled products or reducing the dose of contrast used, the shortage of contrast dye is expected to last for some time. Researchers from UCSF say that several strategies can be implemented to reduce the demand for contrast dye. These include limiting the number of patients who receive the contrast and ensuring that patients with kidney problems have a recent kidney function test before the exam.
What Are the Risks of Contrast Dye?
When you are undergoing an imaging test, such as x-rays, ultrasound, CT scan, or MRI, a contrast dye is usually used to help the doctor see what’s inside your body. These tests are commonly used to diagnose diseases or injuries, and can sometimes help your doctor find treatment for them.
Contrast dyes can be administered by injection or through an enema, or rectal tube (PR). These procedures help the radiologist see your internal organs and blood vessels.
The most common side effects of contrast dyes are allergic reactions and skin rashes. These reactions are usually mild and harmless, but may be severe and cause discomfort.
Another risk is that some patients with kidney disease or diabetes can develop a condition called contrast induced nephropathy or nephrogenic systemic fibrosis. These conditions can lead to kidney damage, and may require dialysis or transplantation if they don’t resolve within a few weeks.
Your doctor or radiologist needs to know how well your kidneys are working before giving you contrast. If your doctor thinks that your kidney function is low, he or she may need to take a blood test before the contrast is given.
These blood tests can also help your doctor determine if you need to have a special type of contrast material. If your doctor thinks that you need a specific type of contrast material, he or she will talk to you about the risks and benefits before you decide to have it.
Iodine-based contrast materials are very safe to use in people with normal kidney function. However, if you have severe kidney disease, you may need to get a different type of contrast before your scan.
Similarly, gadolinium-based contrast agents can also be very safe to use in people with normal kidneys. However, if you have severe kidney failure or have been recently diagnosed with diabetes, your doctor may ask you to wait before getting a gadolinium-based contrast agent because there is a small chance that it could increase the risk of nephrogenic systemic fibrosis.
The osmolality of contrast media compared to the osmolality of plasma, which is made up of water, is thought to play a role in nephrotoxicity. This is because contrast media have high viscosity and have a higher osmolality than plasma. This can be harmful to the kidneys because they are responsible for removing waste and toxins from the body.
What Can I Do to Prevent Contrast Dye Complications?
When you have an imaging exam, such as X-rays, ultrasounds, CT scans or MRIs, contrast is sometimes used to make your organs and blood vessels more visible. This improves your doctor’s ability to diagnose and treat diseases or injuries better.
Contrast does not permanently change anything inside your body. It only changes the way medical imaging equipment sees it.
Your doctor will let you know if contrast is needed and how much it will affect your scan. In general, it takes longer to get clearer scans when contrast is used. This is because it takes time for the dye to be absorbed by the tissues of your body and start working.
Many people can have contrast without experiencing complications, and in fact, it is usually a good idea to have contrast with an imaging test because it will allow your doctor to make a more accurate diagnosis and provide better care for you.
There are some things you can do to prevent contrast dye complications, including making sure you drink plenty of water or other fluids. Also, you should talk to your doctor about any medications you are taking before an MRI because these medications can cause reactions when combined with contrast materials.
You should also let your doctor know if you are pregnant or breastfeeding. If you are breastfeeding, you should stop nursing 24 hours before your scan with contrast so that the dye does not pass into the milk.
Another important thing you can do to reduce the chances of contrast dye complications is to avoid drinking alcohol or taking certain medications before your scan. Those medications can cause your body to absorb contrast material more easily and may make it easier for it to enter the kidneys, causing nephrogenic systemic fibrosis (NSF).
If you have diabetes or have kidney problems, you should ask your doctor about how much IV contrast is safe for you. Some studies have found that patients with these conditions have a higher risk of developing contrast-induced kidney injury, so your doctor will probably want to lower the dose of contrast used in your scan.