- Main risks
- 1. Acute allergic reaction
- 2. Toxic effects of the substance
- 3. Nervous system reactions
- Examples of tests with contrast
Contrast exams, also called contrast exams, are imaging exams made with the use of substances that help to obtain a better definition of the formed images, 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 varied chemical compositions, such as barium sulfate, iodinated contrast or gadolinium, for example, which are chosen according to the test 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, therefore, 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 are better able to assess who should and should not do it, it is possible that these tests do 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 pressure, rapid heartbeat, bronchospasm and glottis edema. The allergic reaction due to the use of contrasts needs to be treated quickly by the doctor in the hospital, as it represents a serious risk to the health of 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 drugs before some tests with higher risk, such as antihistamines or corticosteroids.
2. Toxic effects of the substance
The contrast can have a toxic effect on the body, and some of the reactions include direct effects on the bloodstream, such as pressure drop or inflammation of the application site. In addition, the substance can cause direct toxic effects on certain organs, which may be:
- Skin: pain at the application site, 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 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 can also vary according to the speed of infusion and the form of use of the substance, whether oral or venous, for example.
3. Nervous system reactions
Also known as vasomotor reactions or vagal vessels, 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 falling blood pressure, decreased heart rate, fainting, mental confusion, pallor or cold sweat, for example.
Examples of tests with contrast
Some of the main tests used with contrast are:
- Computed tomography: is usually done with iodinated contrast, widely used to detect lesions in organs of the body, such as the brain, lungs, liver, vesicle, pancreas, bones or abdominal wall, for example, mainly tumors, infections or changes in blood vessels. Find out more details about how it is done and what the CT scan is for; Magnetic resonance imaging: Gadolinium is usually used as a contrast, being an exam used to detect brain or spinal injuries, as well as soft parts of the body such as ligaments, joints and blood vessels; Angiography: iodinated contrast is the most used in this exam, which allows a better view of the inside of blood vessels and to observe diseases such as aneurysms or arteriosclerosis, for example. Understand how it is done and what angiography is for; Urography: it is one of the exams 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, and an examination is performed to observe functional changes in organs such as heart, bones, lungs, thyroid or brain, for example. As contrasts, varied substances are used, some of which are technetium and gallium; Radiological study of the gastro-intestinal tract: there are several tests used to evaluate the digestive tract, which usually use barium sulfate as a contrast, among them the opaque enema, seriography or contrasted radiography, for example; Cholangiography: it is a type of tomography performed to evaluate the biliary tract, and the use of iodinated contrast is common.
In addition to this, there are several other tests that can be done with the aid of contrast, such as mammography to assess changes in circulation in the breast or hysterosalpingography to assess the female reproductive system, for example, which should be indicated by the doctor according to the needs of each person.
