Contrast-enhanced exams, also called contrast-enhanced exams, are imaging exams performed with the use of substances that help to obtain a better definition of the images formed, which facilitates the doctor’s evaluation.
These substances are called “contrast media”, as they are able to absorb ionizing radiation from the exam and generate defined images on the device’s screen. There are different types of contrast, with different chemical compositions, such as barium sulfate, iodinated contrast or gadolinium, for example, which are chosen according to the exam that will be performed, which can be done orally, intravenously or injected into the cavity. desired.
Despite its benefits, the use of contrast for exams contains risks, mainly of causing side effects such as allergic reactions, drop in blood pressure or intoxication of the kidneys and heart, for example, for this reason, they should only be used in specific cases, with adequate medical indication.
Main risks
Although tests with contrast tend to be increasingly safe, and doctors assess who should and should not do it, it is possible that these tests cause some health risks. Some of the main side effects include:
1. Acute allergic reaction
Also called anaphylaxis, this reaction is characterized by the appearance of hives, swelling of the skin, drop in blood pressure, rapid heartbeat, bronchospasm and glottal edema. The allergic reaction due to the use of contrast agents needs to be treated quickly by the doctor in the hospital as it poses a serious health risk to the affected person.
One way to try to avoid this type of reaction is to ask if the person has any type of allergy, and it is also common for doctors to indicate the consumption of anti-allergic medication before some tests with greater risk, such as antihistamines or corticosteroids.
2. Toxic effects of the substance
Contrast can have a toxic effect on the body, and some of the reactions include direct effects on the bloodstream, such as a drop in pressure or inflammation of the injection site. In addition, the substance can cause direct toxic effects on certain organs, which can be:
- Skin: application site pain, redness, swelling or lump formation;
- stomach and intestine: nausea, vomiting or diarrhea;
- Kidneys: reduced urine formation or renal failure;
- Brain: headache, dizziness, mental confusion or seizure;
- Lungs: shortness of breath, bronchospasm or triggering of asthma attacks;
- Heart: increased blood pressure, arrhythmias, cardiac arrest.
Generally, these effects are related to the dose or concentration of the contrast medium used, and may also vary according to the infusion rate and the way in which the substance is used, whether oral or intravenous, for example.
3. Nervous system reactions
Also known as vasomotor or vasovagal reactions, they are not directly caused by the contrast used and their cause is unknown, being normally associated with anxiety or pain during its administration, which causes certain stimuli in the nervous and vascular system.
These reactions include a drop in blood pressure, a slow heart rate, fainting, mental confusion, paleness or cold sweat, for example.
Examples of contrast exams
Some of the main tests used with contrast are:
- Computed tomography: it is usually done with iodinated contrast, widely used to detect lesions in body organs, such as the brain, lungs, liver, gallbladder, pancreas, bones or abdominal wall, for example, mainly tumors, infections or changes in blood vessels. Learn more details about how computed tomography is done and what it is for;
- MRI: Gadolinium is usually used as a contrast, being an exam used to detect brain or spinal injuries, as well as in soft parts of the body such as ligaments, joints and blood vessels;
- Angiography: iodinated contrast is the most used in this exam, which allows you to better visualize the inside of blood vessels and observe diseases such as aneurysm or arteriosclerosis, for example. Understand how angiography is done and what it is for;
- urography: is one of the tests that allows visualizing the anatomy of the urinary tract and assessing the functional capacity of the kidneys;
- Scintigraphy: there are several types of scintigraphy, for different organs of the body, being an exam carried out to observe functional changes in organs such as the heart, bones, lungs, thyroid or brain, for example. Various substances are used as contrasts, some of the main ones being technetium and gallium;
- Radiological study of the gastrointestinal tract: there are several tests used to evaluate the digestive tract, which usually use barium sulfate as a contrast agent, including barium enema, seriography or contrast radiography, for example;
- cholangiography: it is a type of tomography performed to evaluate the bile ducts, and the use of iodinated contrast is common.
In addition to this, there are several other tests that can be performed with the aid of contrast, such as mammography to evaluate changes in circulation in the breast or hysterosalpingography to evaluate the female reproductive system, for example, which must be indicated by the doctor according to the needs. of each person.
