Contrast exams: risks and types

The contrast exams, also contrasted calls, are successful image exams with the use of substances that help to obtain a better definition of the formed images, which facilitates the evaluation of the doctor.

These substances are called “contrast media”, since they are able to absorb the ionizing radiation from the examination and generate defined images on the device’s screen. There are different types of contrast with different chemical compositions such as barium sulfate, iodized or gadolinium contrast, which are chosen based on the exam that will be carried out, and which can be ingested orally, intravenously or injected into the desired cavity.

Despite its benefits, the use of contrast for exams contains risks, mainly it can cause side effects such as allergic reactions, drop in blood pressure or intoxication of kidneys and heart, so they should only be used in specific cases and under the medical indication.

Examples of contrast tests

Some of the main tests used with contrast are:

• Computed tomography (CAT): It is generally carried out with iodinated contrast, very used to detect lesions in organs such as the brain, lungs, liver, gallbladder, pancreas, bones or in the abdominal wall, mainly tumors, infections or alterations in blood vessels. Know the advantages and disadvantages of the tomography.
• magnetic resonance: if you use the Gadolinio as a contrast, it is a test used to detect brain lesions or in the vertebral column, as well as in the soft parts of the body such as ligaments, joints and blood vessels;
• Angiography: the yodado contrast is the most used in this exam, which allows to better visualize the interior of the blood vessels and observe diseases such as aneurysm or arteriosclerosis, for example. Understand how it is done and to serve the angiography. Find out how the angiography is performed;
• Urography: it is one of the exams that allows to visualize the anatomy of the urinary apparatus and to evaluate the functional capacity of the kidneys;
• gammagraphy: there are different types of gammagraphy for different organs of the body, being a test used to observe functional alterations in organs such as the heart, huesos, lungs, thyroid or brain, for example. As a contrast, several substances are used, including some of the principals and technetium and galio. Find out more about the indications and how to perform bone gammagraphy and myocardial gammagraphy.
• Radiological study of the gastrointestinal tract: there are several exams used to evaluate the digestive tract that require the use of barium sulfate as a contrast, among which are barium enema, serigraphy or contrasted radiography, for example;
• cholangiography: it is a type of hecha tomography to evaluate the bile ducts, being very common in the use of yodated contrast.

In addition, there are other tests that can be performed with contrast aid, such as mammography to assess changes in breast circulation or hysterosalpingography to assess the female reproductive system, for example, which should be indicated by a doctor in accordance with the individual needs of the person.

main risks

Despite the fact that the tests with contrast tend to be more and more reliable, in addition to that the doctors also evaluate more and more what they owe or not, it is possible that these tests cause some risks to health. Some of the main secondary effects include:

1. Acute allergic reaction

Also called anaphylaxis, this reaction is characterized by the appearance of urticaria, skin swelling, pressure drop, rapid heart rate barking, bronchospasm and glottis edema. It needs to be treated quickly by the doctor at the hospital, 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, it is also common for doctors to indicate the consumption of some antiallergic before taking any exam that has a greater risk, such as antihistamines or corticosteroids. Learn more about why anaphylactic shock occurs and how to treat it.

2. Toxic effects of the substance

The contrast can have a toxic effect on the organism, and some of the reactions include direct effects on the blood stream such as pressure drop or inflammation of the site where the contrast is applied, which can cause direct toxic effects in certain organs such as:

• skin: pain in the area where it was applied, reddening, swelling or formation of nodules;
• stomach and intestine: nausea, vomiting or diarrhea;
• Riñones: reduction of urine formation or renal failure;
• Brain: headache, mareo, mental confusion or convulsion;
• lungs: shortness of breath, bronchospasm or can trigger an asthma attack;
• heart: increase in blood pressure, arrhythmias and cardiac arrest.

Generally, these effects are related to the dose or concentration of the contrast medium used, and they can also vary from according to the infusion speed and the way in which the substance is used, whether it is decided, whether it is through the oral route or of the intravenous route.

3. Nervous system reactions

Also known as vasovagal reactions, they are not caused directly by the contrast medium used and their causes are unknown, being normally associated with anxiety or pain during the administration of the substance, causing certain stimuli in the nervous and vascular system .

These reactions include drop in blood pressure, decrease in heart rate, fainting, mental confusion, paleness and cold sweating.