Contrast agent for CT: side effects and contraindications. Adverse reactions and complications with the introduction of radiopaque substances, their prevention and elimination measures Contrast tomography

Contrast-enhanced CT is used to improve image quality and detect some pathological structures. The procedure helps to determine the extent of the disease. In this article, we will consider the main indications and contraindications for computed tomography with a contrast agent.

Computed tomography is a hardware-software study of the liver. The essence of the procedure is the translucence of the patient's body with X-rays. The doses that are used for irradiation do not pose a serious danger to the body.

The data obtained are transmitted to the patient 90 minutes after the study. They may be stored on a digital medium.

Note! CT can detect cirrhosis or liver cancer at an asymptomatic stage.

CT without contrast

Computed tomography without contrast agent helps to obtain information about:

• inflammatory processes in the liver;
• neoplasms;
• disproportions of the studied organ.

The information content of CT without contrast is not 100%. The cause of the pathological processes occurring in the liver can only be found out with the help of a radiopaque preparation.

Methods for introducing a contrast agent

The main methods of introducing a radiopaque preparation are presented in the table.

Table 1. How is the contrast medium administered?

Features of the procedure

Having identified the disease, the doctor has the opportunity to choose a therapeutic tactic or make adjustments to an existing scheme. If the pathology is detected at an early stage, the chances of curing the patient without surgical intervention increase.

Table 2 Benefits of the procedure.

Indications for carrying out

Computed tomography is performed against the background of unsatisfactory test results. Research is also recommended if there is a suspicion of the development of a particular disease.

Table 3. Other indications for CT.

Also, the procedure is carried out in order to identify postoperative complications.

Main contraindications

In some cases, a CT scan with contrast should be abandoned.

Table 4. What are the contraindications?

Possible risks

The procedure of computed tomography with contrast involves irradiation of the body. Note! A single use of a radiopaque preparation does not lead to sad consequences. Against the background of accumulation of radiation in the tissues, it is categorically not recommended to undergo such diagnostics often. This can result in the development of cancer.

With the development of Quincke's edema, the patient is given an emergency drug. This helps to quickly normalize the patient's condition.

Computed tomography is always performed in the presence of an anesthesiologist. The specialist quickly provides assistance in the event of side effects provoked by background pathologies.

Carrying out computed tomography

There are several types of liver CT. Detailed information about them is presented in the table.

Table 5. Main types of computed tomography.

The procedure involves the use of ionic and non-ionic preparations containing iodine.

The use of ionic drugs

Table 6. Use of ionic drugs.

The use of non-ionic drugs

These drugs rarely cause side effects. Therefore, preference is given to them.

Preparation for the procedure

The instruction looks like this:

1. Identification of contraindications to computed tomography. The patient is recommended to take a blood test for creatinine, as well as urine. If symptoms of kidney failure and iodine allergy are identified, CT should be abandoned in favor of alternative diagnostic methods.
2. Refusal of food. It is recommended not to eat 6-7 hours before the start of the procedure.
3. Refusal of alcohol and tobacco products. Drinking and smoking are not allowed 12 hours before the CT scan.
4. Notifying your doctor about your health condition. It is necessary to inform the specialist not only about existing concomitant diseases, but also about phobias. This is especially true for people who experience a panic fear of a closed space.
5. Administration of a sedative. Recommended against the backdrop of strong experiences. When taken orally, it is allowed to drink the medicine with tea or any other non-alcoholic drink.
6. In the evening before the procedure, it is allowed to take a medicine that creates a contrast effect.
7. In the morning before computed tomography, the patient undertakes to cleanse the intestines. This can be done with a herbal laxative or an enema.
8. It is recommended to drink 2000 ml of non-carbonated water 2-3 hours before the diagnosis.
9. Clothing should be comfortable and not restrict movement. Before starting a CT scan, it is recommended to remove all jewelry, including the pectoral cross.

Important nuances

Bolus drug administration is preferred over all other methods. The drug is administered by drip.

The effectiveness of the study depends on the following factors:

• the rate at which the drug is administered;
• the amount of medication administered;
• drug concentration.

Note! The main reason for erroneous diagnosis is the slow administration of the drug with a low concentration.

The amount of medication administered depends on the weight of the patient. The higher it is, the larger the volume. The radiation dose for liver examination is about 8 mSv.

Procedure technique

A tomograph is used for computed tomography. The device operates on the basis of sensors with x-ray radiation. The sensors show the tissues of the organ under study in numerous sections.

Table 8. How is the procedure carried out?

In order to maximize the cleansing of the body from the contrast agent after the procedure, the patient will have to drink a large amount of water. Preference is given to non-carbonated mineral water. The contrast agent is excreted through the kidneys.

The obtained data of computed tomography are carefully studied by the doctor. Only then is a diagnosis made.

The main stages of the study

The main stages of the procedure are presented in the table.

Table 9. 3 stages of computed tomography.

Possible side effects

During the procedure, the patient should closely monitor their well-being. Safe side effects provoked by the introduction of a contrast agent include:

• metallic taste in the mouth;
• sensation of heat in the whole body;
• burning at the injection site.

More dangerous symptoms are presented in the plate.

Table 10. Anxiety symptoms.

Note! Communication between the patient and the medical staff is carried out using a microphone and a push-button device. If dangerous symptoms appear, it is necessary to notify the doctor as soon as possible.

What affects accuracy?

The following factors influence the quality of computed tomography results:

• a recent examination with barium-based contrast;
• recent diagnostics involving the use of a special amplifier;
• the presence of surgical clamps in the peritoneum.

Deciphering the results

What the computed tomography of the liver shows can be seen in the conclusion. When deciphering the picture, the specialist pays attention to the nuances that help him establish an accurate diagnosis.

Absence of pathology

The parameters indicating the absence of the disease are presented in the plate.

Table 11. Norm.

Deviation from the norm

The table shows the parameters indicating the presence of the disease.

Table 12. Deviations from the norm.

Alternative Research Methods

Rarely, CT is replaced by ultrasound.

The main advantage of ultrasound is lower cost. The price of computed tomography varies from 7.3 to 7.8 thousand rubles. The cost of ultrasound ranges from 700-1500 rubles.

Conclusion

For the purpose of a comprehensive study of the liver, the patient is recommended to undergo PETCT. This is the latest development of nuclear medicine, which explores abnormal changes in real time.

More detailed information about the features of computed tomography can be found in the video in this article.

MRI diagnostician

Head of the department, doctor of medical sciences.

Computed tomography is an examination of the body that uses X-rays to produce a series of images of the internal structure of the body.

This diagnostic option allows you to examine tissues, vessels, organs as a whole from all sides, from the inside, in section, to identify injuries, hematomas, tumors.

CT scans are more accurate and result in much more detailed images than x-rays. For greater detail of the picture, if required, the patient is offered to inject a contrast agent.

Computed tomography with contrast - what is it?

CT with contrast is performed in cases where it is necessary to clearly separate normal and pathological structures in the human body, to differentiate organs by amplifying the signal received from veins and arteries. In the image, the contrast is highlighted in white, which allows you to see the details of the selected area of ​​​​the body and make an accurate diagnosis.

A contrast agent at CT is usually injected into the cubital vein, but there is an option when the patient drinks the solution with it (only for the diagnosis of the organs of the gastrointestinal tract).

It enters the blood in one of two ways:

1. Manual;
2. Bolus.

In the first option, the injection is made directly by the health worker, while in the second, a special injector syringe is used with a normalized rate of supply of the substance (3 milliliters per second). Thanks to this, experts easily calculated how many seconds after the contrast was received, an image could be captured in one or another part of the body.

contrast agent

Many patients are interested in what drug is administered intravenously during CT with contrast? Answer: These are iodine-containing substances. It is iodine that increases the intensity of the image. Water-soluble preparations are quickly absorbed by tissues, therefore, in most cases, they are used. Substances are ionic (the most common, cheaper) and non-ionic (expensive, less toxic).

Before introducing a contrast agent, the doctor determines the presence or absence of an allergy in a patient, as well as diseases in which contrast is contraindicated. Are tests necessary for CT with contrast? Yes, because this type of diagnosis has a number of contraindications:

• allergic reaction;
• bronchial asthma;
• diabetes mellitus (severe form);
• thyroid disease;
• kidney failure;
• myeloma.

The patient will need to take a blood test for biochemical composition. As a result, indicators of the level
urea, transaminase, creatinine. Thus, a picture is compiled of the patient's condition before the start of the study - if functional activity is insufficient, there are any of the above diseases, abnormalities, it will not be possible to perform CT with contrast.

Also unacceptable is any computed tomography (with and without contrast) for pregnant women and people who are overweight (the device has a limit in kilograms).

CT scan with contrast, which drug is administered intravenously is a request of interest to people who want to get the most detailed information in order to protect themselves from side effects and undesirable effects on the body. Below is a list of iodine-containing substances.

Contrast for ct name, composition:

1. Iopromide, non-ionic;
2. Metrizoate, ionic;
3. Diatrizoate, ionic;
4. Ioxaglat, ionic;
5. Yomeprol, non-ionic;
6. Iohexol, non-ionic;
7. Iopamidol, non-ionic;
8. Iodixanol, non-ionic;
9. Ioversol, non-ionic.

Survey

Prior to the start of the CT scan, the doctor must give comprehensive information about this procedure. In particular, after the introduction of a contrast agent, the patient should increase the daily intake of water to three liters - this will help to remove the contrast from the body.

The examination process is painless and relatively fast (time depends on the specific situation). The patient will need to remove all jewelry and items that contain metal, if given the opportunity, change into a special gown.

With manual contrast, an intravenous injection is given, and with a bolus, the health worker installs a syringe dispenser with a contrast agent. The patient is covered with radiation protection, placed on a special table, which lifts him into the radiation zone of the device.

As early as 15-18 seconds after the drug enters the bloodstream, images of the ascending aorta and heart vessels can be obtained after 25 seconds. - aorta. As mentioned above, the farther the diagnosed organ is from the heart, the more time must elapse before the start of the study.

The image is displayed on the computer screen. The doctor fully controls the process of computed tomography and sees all its stages during the examination. Undoubtedly, this is a significant plus, because the patient can communicate with the doctor and report problems if they arise. It relieves emotional stress.

By the way, a person is not completely placed in the device, the feeling of a closed space is not created - even people with claustrophobia endure the research process well.

Conclusion

Computed tomography is a modern method for diagnosing various formations in the body, abnormalities in the work of blood vessels, and the consequences of injuries. For this, there is X-ray radiation, as well as a special apparatus.

Thanks to contrast-enhanced CT, the doctor receives the most detailed layer-by-layer image of organs and tissues in the body by amplifying the return signal. However, not all patients can be injected with contrast - for this, a blood test must be taken before the procedure. Immediately after the examination, the person can return to daily life.

Content

An important computed diagnostic is abdominal CT with contrast enhancement of the internal organs, which is necessary to show the alleged foci of pathology. In this way, it is possible to assess the state of the peritoneum and retroperitoneal space along with the vessels and abdominal lymph nodes. Computed tomography of the abdominal cavity with a contrast agent is performed in a hospital, making it easier to make a final diagnosis.

What is a CT scan of the abdomen

This informative diagnostic method is necessary for visualization of organs where the pathology foci are presumably located. Such a clinical examination is appropriate for diseases of the kidneys, stomach, adrenal glands and other structures of the abdominal, retroperitoneal space. In addition, CT of the abdominal organs is necessary to assess the real state of the vessels close to the foci of the pathology of the lymph nodes. Any changes in the structure of the internal organs are visible on the screen, but this occurs mainly after the introduction of contrast.

Indications

CT of the retroperitoneal space and peritoneum can be performed strictly for medical reasons after preliminary preparation of the patient. The computer procedure is performed with contrasting - for a kind of "highlighting" the internal organs, presumable foci of pathology. The need to perform layered images for diagnosis arises in the following clinical pictures:

• damage to the lymph nodes;
• blood diseases;
• abscesses, phlegmon;
• benign and malignant tumors, cysts;
• atherosclerosis and other extensive vascular lesions;
• stones in the gallbladder and kidneys;
• the presence of a foreign body in the intestine;
• cirrhosis, hepatitis, other liver damage;
• echinococcosis;
• trauma and hemorrhage.

In addition, doctors prescribe CT of the internal organs to the patient in preparation for surgery, after the operation for strict control of treatment and the rehabilitation period. This is a good opportunity to avoid exacerbation of inflammatory processes, other potential complications in the course of improperly selected intensive care.

What organs are checked during CT

Computed tomography examines in detail the internal organs of the peritoneum and retroperitoneal space, studies the lymphatic system and the general condition of the vessels, their permeability. For example, such a progressive method can be used to examine the pancreas, to determine in a timely manner the causes of progressive endocrine disorders. The indicated diagnostics is appropriate for studying the structure of organs of other internal systems of the human body. Among those:

• liver;
• kidneys;
• spleen;
• stomach;
• intestines;
• gallbladder;
• adrenal glands;
• pelvic organs;
• blood vessels;
• urinary tract;
• lymphoid tissues.

Contraindications

CT scan of the peritoneum can be performed not for all patients, there are limitations. The study itself is safe, since the radiation entering the body with the longest possible diagnosis does not exceed the average dose of an X-ray of the gastrointestinal tract. Absolute contraindications are the weight of the patient from 120 kg, increased emotionality of the patient, the period of pregnancy. Relative limitations to performing CT of the peritoneum are presented below:

• children's age up to 14 years;
• inflammatory processes in the kidneys;
• lactation period (for the procedure with contrasting);
• acute allergic reaction to contrast agents;
• diabetes mellitus (for CT with contrast);
• blood diseases;
• complicated pathologies of the liver and cardiovascular system.

Types of CT

CT of the abdominal aorta is performed using special medical equipment, which is structurally a three-dimensional ring with a progressively retractable table, where the patient is placed for examination. In practice, there are the following types of computed tomography:

1. Spiral CT. The X-ray tube makes translational movements around the patient, at the same time the table on which the patient lies rotates. The procedure is extremely safe.
2. Multilayer CT. The sensors that receive the allowable dose of radiation are placed in several rows and remain motionless. As a result, the doctor receives informative three-dimensional images.
3. Multislice CT. The scanning process has been significantly increased in speed and resolution, and for this, two main radiation sources are used.

Preparing for an Abdominal CT Scan

Special preparation for computed tomography of the abdominal organs is required, which includes a complete refusal to eat for 8 hours before the computer study. This procedure is carried out on an empty stomach, otherwise, with a filled gastrointestinal tract, it is not at all possible to speak of the high information content of the CT method. You can pre-cleanse the filled intestines with an enema in a hospital setting or at home.

Oral Urografin before CT

The specified medical preparation is required for contrasting, since an increased concentration of iodine predominates in its chemical composition. This active component of Urografin absorbs most of the X-rays, thereby enhancing the contrast and improving the image quality during CT scans. A characteristic medication is excreted naturally in a few days without side effects and potential complications.

How is a CT scan of the abdomen done?

Virtual colonoscopy is performed with and without a contrast agent, the information content of the computer method depends on this. Native CT is performed without the use of contrast, shows the general condition of the internal organs of the abdominal cavity. The sequence of actions in a clinical trial is as follows:

1. The patient is required to remove all metal objects, jewelry.
2. The patient should lie on a sliding table on his back.
3. The table moves into the tunnel of the apparatus, and communication with the patient proceeds with the help of a microphone and speakers.
4. When the table rotates, the tomograph takes several informative pictures.
5. If the image quality is decent, the table leaves the tomograph ring.

Abdominal CT with contrast

With intravenous administration of a contrast agent, internal organs are additionally highlighted, which is especially appropriate for suspected metastases, malignant tumors, and cysts. The resulting image shows the exact shape and size of the progressive neoplasm, the location of the focus of the pathology. Reviews of specialists who regularly use bolus contrast to make a final diagnosis are positive and report that this diagnostic method is more informative for future treatment.

Decryption

The research method is safe, excludes trauma to the abdomen, internal organs, exposure to an increased dose of radiation. If no pathology is observed in the body, the doctor sees this on the screen of the tomograph. But in the presence of a pathological process, the following deviations occur, requiring conservative or surgical treatment:

• abdominal tumors;
• inflammatory bowel processes;
• kidney stones, foreign bodies;
• obstruction of the intestines or bile ducts;
• swollen lymph nodes.

How often can a CT be done

Performing CT with contrast is not recommended as often, since an increased dose of iodine in the body can provoke side effects, increasing symptoms of intoxication. By itself, the dose of radiation during CT is not dangerous, it does not cause significant harm to the patient's health. Re-diagnosis is carried out in emergency cases to clarify the final diagnosis. CT without contrast has a less categorical time frame, fewer side effects.

Price

The cost of the procedure depends on the city of residence of the patient, the rating of the diagnostic center and the reputation of a particular diagnostician. You can try to examine the abdominal cavity for free in the district clinic, but not all medical institutions are equipped with professional tomographs, they have graduates in a given direction. Approximate prices for CT in Moscow and the region are presented in the following table.

Application radiopaque drugs poses the greatest danger to patients due to the high frequency and severity of complications. Harmful effects of water-soluble radiopaque agents (RCM) used for excretory urography, renal CT, AGP and CT angiography, and other renal and urinary tract examinations are associated with chemotactic effect iodine, carboxyl groups on cells; with osmotic toxicity and local ionic imbalance that occurs in the lumen of the vessel during the bolus administration of ionic radiopaque agents. Phenomenon osmotic toxicity consists in a multiple increase in osmotic pressure at the injection site, which causes dehydration and damage to endothelial cells and blood cells. As a result, erythrocytes lose their elasticity and the ability to change shape when moving through the capillaries, there is an imbalance between the formation of endothelin, endothelial relaxing factor (NO), the production of other biologically active molecules is activated, the regulation of vascular tone and microcirculation are disturbed, and thrombosis occurs.

The toxicity of RCS is determined by the structure of their molecule and its ability to dissociate into ions in an aqueous solution. Until recently, only ionic or dissociating radiopaque agents (urographin, verografin, etc.), which consist of salts that dissociate into cations and anions. They are characterized by high osmolarity (5 times higher than that of blood plasma), therefore they are also called high osmolar contrast agents and can cause local ion imbalance. When using them, side effects often develop, up to the most severe. are more secure non-ionic or non-dissociating, low osmolar radiopaque agents (iohexol, iopromide, iodixanol). They do not dissociate into ions, are characterized by a higher ratio of the number of iodine atoms to the number of drug particles per unit volume of the solution (that is, good contrast is provided at a lower osmotic pressure), iodine atoms are protected by hydroxyl groups, which reduces chemotoxicity. At the same time, the cost of low-osmolar radiopaque agents is several times higher than that of high-osmolar ones. In addition, radiopaque agents are divided according to their structure into monomeric and dimeric, depending on the number of benzene rings with embedded iodine atoms. When using dimeric drugs containing six instead of three iodine atoms in one molecule, a smaller dose of the drug is required, due to which osmotoxicity is reduced. According to the mechanism of development, side effects are divided into:

• anaphylactoid, or unpredictable(anaphylactic shock, angioedema, urticaria, bronchospasm, hypotension);
• direct toxic(nephrotoxicity, neurotoxicity, cardiotoxicity, etc.);
• local(phlebitis, soft tissue necrosis at the injection site).

Anaphylactoid, or unpredictable, reactions to iodine-containing contrast agents are so named because the cause and exact mechanism of their development are not known, although certain conditions increase their risk. There is no clear relationship between their severity and the dose of the administered drug. A certain role is played by the activation of the secretion of serotonin and histamine. The difference between anaphylactoid reactions and true anaphylaxis in practice is not significant, since the symptoms and treatment measures do not differ in them.

By severity, side effects are divided into mild (not requiring intervention), moderate (requiring treatment, but not life-threatening) and severe (life-threatening or leading to disability).

To mild side effects include the appearance of sensations of heat, dry mouth, nausea, lack of air, headache, slight dizziness. They do not require treatment, but may be harbingers of more severe effects. If they occur before the end of the introduction of a contrast agent, it is necessary to stop it. Without removing the needle from the vein, continue monitoring the patient, prepare medications in case of more severe complications.

With the development of side effects moderate severity(severe nausea, vomiting, rhinoconjunctivitis, chills, itching, urticaria, Quincke's edema) an antidote is administered - sodium thiosulfate (10-30 ml of a 30% solution intravenously), adrenaline (0.5-1.0 ml of a 0.1% solution subcutaneously) , antihistamines - diphenhydramine (1-5.0 ml of a 1% solution intramuscularly), chloropyramine (1-2.0 ml of a 2% solution intramuscularly), prednisolone (30-90 mg intravenously in a glucose solution). In the case of tachycardia, a drop in blood pressure, the appearance of pallor, adrenaline is additionally injected (0.5-1.0 ml intravenously), oxygen inhalation is started in a volume of 2-6 l / min. When signs of bronchospasm appear, bronchodilators are prescribed in the form of inhalations.

With the development severe anaphylactoid reaction or true anaphylactic shock(pallor, a sharp drop in blood pressure, collapse, tachycardia, status asthmaticus, convulsions), it is necessary to call a resuscitator, install a system for intravenous infusions and start inhalation of oxygen 2-6 l / min. Sodium thiosulfate (10-30 ml of a 30% solution), adrenaline 0.5-1.0 ml of a 0.1% solution, chloropyramine 1-2.0 ml of a 2% solution or diphenhydramine 1-2.0 ml of a 1% solution are injected intravenously , hydrocortisone 250 mg in isotonic sodium chloride solution. If necessary, the resuscitator performs intubation and artificial ventilation of the lungs.

To the development of such a severe complication as acute heart failure, can lead to dysregulation of the heart (hyperactivation of parasympathetic influence, leading to severe bradycardia and a decrease in cardiac output), myocardial damage due to its ischemia and direct toxic effect of a contrast agent with the development of arrhythmia and a decrease in the pumping function of the heart, a sharp increase in afterload in the systemic and pulmonary circulation due to vasoconstriction and impaired microcirculation. With hypotension resulting from vagal vascular reaction and associated, in contrast to anaphylactoid hypotension, with severe bradycardia, in addition to intravenous administration of isotonic sodium chloride solution, atropine (0.5-1.0 mg intravenously) is used. In acute left ventricular failure, inotropic agents (dopamine, 5-20 mcg/kg/min) are administered intravenously. With normal or high blood pressure, nitroglycerin (0.4 mg sublingually every 5 minutes or 10-100 µg/min) is used to reduce afterload, sodium nitroprusside (0.1-5 µg/kg/min) to reduce afterload.

NB! Adverse reactions to contrast agents in history - an absolute contraindication for their repeated use.

Risk factors for complications when using iodine-containing contrast agents:

• previous allergic reactions to drugs;
• history of allergies;
• bronchial asthma;
• severe heart disease, lung;
• dehydration;
• chronic renal failure;
• old and old age.

Prevention of complications consists in a careful history taking and examination before the study by the attending physician in order to identify risk factors. In the presence of at least one of them, and especially when they are combined, a thorough and rigorous assessment of the ratio of potential benefits and dangers of the planned study is required. It should be carried out only if its results can affect the tactics of treatment and thereby improve the prognosis and quality of life of the patient. The most important preventive measure is the use of low-osmolar (non-ionic) RCS, at least in patients at risk. According to numerous studies, the frequency of side effects when using high-osmolar contrast agents is 5-12%, low-osmolar - 1-3%. In the event of a reaction, assistance is already provided in the diagnostic room, where the necessary set of medicines should be at hand. Some centers have adopted premedication with prednisolone in patients at risk to prevent anaphylactoid reactions (50 mg orally 13, 5, and 1 hour before contrast agent administration). However, there is no convincing evidence that this preventive measure significantly reduces the risk of complications, so its widespread implementation should be recognized as insufficiently justified.

The nephrotoxicity of RCS requires special consideration. It consists of a direct toxic effect of the drug on the epithelium of the renal tubules and renal endothelium, as well as osmotic toxicity. Severe endothelial dysfunction occurs with increased production of both vasopressor and vasodilator agents endothelin, vasopressin, prostaglandin E 2 , endothelial relaxing factor (NO), atrial natriuretic peptide; however, there is an earlier exhaustion of the depressor system with a predominance of vasoconstriction. As a result of this, as well as an increase in blood viscosity and a deterioration in microcirculation, glomerular perfusion is disturbed, ischemia and hypoxia of the tubulointerstitium develop. Under conditions of hypoxia and increased osmotic load, the epithelial cells of the renal tubules die. One of the factors affecting the epithelium of the renal tubules is the activation of lipid peroxidation and the formation of free radicals. Fragments of destroyed cells form protein casts and can cause obstruction of the renal tubules. Clinically, kidney damage is manifested by proteinuria and impaired renal function - from reversible hypercreatininemia to severe acute renal failure, which can occur with or without oliguria. The prognosis for the development of acute renal failure in response to the introduction of radiopaque agents is serious. Every third patient with oliguric acute renal failure has an irreversible decrease in kidney function, while half require permanent hemodialysis treatment. In the absence of oliguria, chronic renal failure develops in every fourth patient, and every third of them needs constant treatment with hemodialysis.

The proven risk factors for acute renal failure with the use of radiopaque agents largely coincide with the risk factors for extrarenal complications. These include:

• chronic renal failure;
• diabetic nephropathy;
• severe congestive heart failure;
• dehydration and hypotension;
• high dose and frequency of reintroduction of radiopaque agents.

If in the general population, nephrotoxicity of radiopaque agents, defined as an increase in serum creatinine by more than 0.5 mg / dL or more than 50% of the initial level, is observed in 2-7% of cases, then in patients with impaired renal function (creatinine serum more than 1.5 mg / dl) or other proven risk factors, it is noted in 10-35% of cases. In addition, such probable risk factors for deterioration of kidney function as arterial hypertension, widespread atherosclerosis, impaired liver function, and hyperuricemia should be taken into account. An adverse effect on the risk of myeloma nephrotoxicity and diabetes mellitus without kidney damage has not been proven.

Prevention of acute renal failure with the use of RCS includes:

• taking into account risk factors and contraindications;
• conducting research with RCS in patients at risk, only in cases where its results can significantly affect the prognosis;
• the use of safer low-osmolar drugs;
• the use of the lowest possible doses;
• hydration of patients within 12 hours before and after the study;
• normalization of blood pressure.

Among the medical prescriptions offered for the prevention of acute renal failure with the use of radiopaque agents, only hydration significantly improves the prognosis of patients. The effectiveness of other methods based on prospective clinical studies is doubtful (prescription of dopamine, mannitol, calcium antagonists) or insufficient evidence (prescription of acetylcysteine).

In MRI, for the purpose of contrasting, preparations containing the rare earth metal gadolinium, whose atoms have special magnetic properties, are used. The toxicity of gadolinium preparations is significantly lower (by 10 or more times compared to iodine-containing RCS) due to the fact that its atoms are surrounded by chelate complexes of diethylenetriamidepentaacetic acid. However, when using it, severe side effects of the anaphylactoid type are described, similar to the side effects of iodine-containing RCS, as well as cases of acute renal failure. The tactics of treating these complications does not differ fundamentally compared to the complications of radiopaque agents.

CT with contrast is not prescribed in every case of using the computed tomography technique. This method of examination is very accurate, allowing you to examine even the smallest tumors, blood clots and hematomas, and is used if it is necessary to detail the picture of the disease.

Contrast-enhanced CT is a study that involves the use of X-rays in minimal doses, as well as the introduction of a special substance to enhance the contrast of healthy and pathologically altered tissues. CT with contrast is performed in cases where it is necessary to very clearly distinguish between normal and abnormal structures in the human body. This differentiation is achieved by amplifying the signal from diseased tissues.

The contrast effect of CT is based on the fact that most tumors, especially malignant ones, have a better blood supply than healthy tissues. Therefore, the contrast agent will accumulate in them, giving a picture of difference from other tissues. In addition, contrast is necessary to study the state of blood vessels - veins, arteries. On CT images, the contrast will be highlighted in white, which will allow you to study this area well.

CT with contrast and oncology

1. Tumors of parenchymal organs of the abdominal cavity and retroperitoneal space (with kidney cancer, carcinoma of the liver, pancreas, spleen).
2. Cancer of hollow organs of the peritoneum - intestines, gallbladder.
3. Formations of the chest - lungs, mediastinum, heart.
4. Tumors of the brain and base of the skull.
5. Neoplasms of the musculoskeletal system - bones, ligaments, joints, spine.

Contrast-enhanced tomography will make it possible to distinguish between a banal and common kidney cyst from renal cell carcinoma or benign lipoma, angioma. When examining the state of the liver, CT will help differentiate between cirrhosis, benign tumors, and hepatocellular carcinoma.

A study is used for lymphomas - to distinguish them from another cancer (lymphogranulomatosis) or from simple lymphadenitis. Contrasting will allow you to establish the degree of cancer, its prevalence, damage to regional lymph nodes, the presence of metastases. Often, CT is also prescribed for malignancy of benign tumors, which will be noticeable by a number of specific signs (vascularization, increase in size, etc.).

Other indications for CT with contrast agent

The procedure is very informative in the diagnosis of intraluminal thrombi, as well as thrombosed aneurysms, areas of narrowing of the aorta by thrombi. Also, the contrast will allow a detailed study of vascular malformations, including before surgery to remove them. The examination will give a complete picture of the thinning of the walls of the veins, deep vein varicose veins and thrombophlebitis, as well as atherosclerosis of the arteries.

What else will a tomography with contrast show? These are any diseases of such areas of the body:

1. Hollow organs - stomach, intestines, esophagus.
2. Lungs, bronchi and trachea.
3. Larynx and vocal cords.
4. Brain, spinal cord.
5. Bases of the skull.
6. All parts of the spine.
7. Bones.
8. Jaws.
9. Nose and sinuses.

Contrast agent and route of its administration

Various preparations are used for the procedure - ionic and non-ionic, with iodine content. It is iodine that increases the intensity of the image, while the harm from its penetration into the body is practically absent. The most common are ionic drugs, but non-ionic ones are even more preferred (their toxicity is zero). Ionic agents include Metrizoat, Diatrizoate, Ioxaglat, non-ionic agents include Iopromide, Iopamidol, Iohexol and others.

Before the introduction of the drug, the doctor must clarify the presence of certain diseases and conditions in the patient, which may become contraindications to the procedure. Also, in most clinics, before the examination, the patient must pass a series of laboratory tests (blood biochemistry, general analysis, liver and kidney tests). The amount of contrast agent is calculated based on the person's weight.

There are different ways to introduce contrast, the main ones are as follows:

1. Bolus. With the bolus method of administration, a syringe-injector is installed in the cubital or other vein, in which the rate of drug delivery is normalized.
2. Single intravenous. The drug is injected into a vein once with a conventional syringe.
3. Oral. In this case, the drug is taken by mouth.
4. Rectal. To scan the intestines, a contrast agent is injected through the rectum once.

CT with contrast - all contraindications

The introduction of iodine-containing drugs is prohibited when:

• Severe form of bronchial asthma and diabetes
• Allergies to the contrast agent
• Hyperthyroidism and a number of other thyroid diseases
• severe renal failure
• multiple myeloma

Pregnancy is a strict contraindication to any CT scan, because the study involves the use of x-rays. Relative contraindication - breastfeeding: after the procedure, breastfeeding should be excluded for 1-2 days. The tomograph has a patient weight limit, and when performing a CT scan in people weighing more than 200 kg, it may be difficult.

How often can a CT scan be done with contrast?

It is generally recommended not to perform the procedure more than once every 6 months. This limitation is not due to the use of contrast, but to the radiation exposure received during CT. However, this burden is minimal, and CT scans may be performed more frequently for health reasons.

It should be remembered that a number of patients (1-3%) have pathological reactions to the administration of a contrast agent, which can also limit the frequency of the procedure. These reactions include:

• swelling of the face
• Dyspnea
• Rash on the body
• Hives
• Skin itching
• Bronchospasm
• pressure drop
• Nausea
• Vomiting, etc.

Such reactions are considered signs of an allergy to the contrast agent and require medical attention. Normal are only a slight metallic taste in the mouth, pain in the injection area, a feeling of warmth in the body.

How the study is done

Preparation for contrast-enhanced CT includes the following measures:

• Do not eat for 4-8 hours before the procedure (depending on the specific study area)
• Take a drug to reduce gas formation (when examining the digestive tract)
• Come in comfortable, loose clothing
• Remove all metal jewelry, removable medical devices

The patient is placed on the couch, injected with a contrast agent, or a syringe-injector is installed. After a certain period of time, the scanning procedure begins - a person is rolled under the arc of the tomograph and a series of images is taken. The farther the studied organ is located from the heart, the longer it takes the contrast to stain it.

CT with or without contrast: the main differences

When examining hollow organs, conventional native CT without contrast will show them as a homogeneous gray mass without highlighting. If a contrast agent is injected, the walls of the organs will be stained, which will make it possible to consider any diseases of their mucous membrane and muscle layer.

During the study of blood vessels, only the penetration of a contrast agent into them will make it possible to identify blood clots and plaques of atherosclerosis, as well as to detail the boundaries of aneurysms, narrowings and plexuses of blood vessels among themselves. Native CT will not provide such accurate information even when the "vascular mode" is enabled.

When diagnosing cancerous tumors, the differences between the procedure with and without contrast are most pronounced. It is malignant neoplasms that feed on the largest number of vessels, therefore they are painted clearly, brightly, with visible borders. Therefore, often after a native CT scan, on which a tumor is detected, contrast-enhanced CT scan is recommended to clarify the diagnosis.

In general, the differences between the procedures are as follows:

1. Contrast-enhanced CT in one examination provides much more information for the doctor.
2. Computed tomography with contrast makes images of individual anatomical zones more detailed and clear.

Diseases for which computed tomography with contrast is used:

• Cancer tumors
• polyps
• cysts
• adenomas
• Lipomas
• Blood clots
• Vascular malformations
• Aneurysms
• Ulcers and erosion
• Stenosis of veins and arteries
• aortic stenosis
• Aortic dissection
• vascular atherosclerosis
• Bronchial asthma
• bronchiectasis
• Abscesses
• Phlegmon

CT is a modern study that will help to find various pathologies in the body, often not detected by other methods. The contrast agent during CT will allow you to clearly visualize all abnormalities and diseases in a fast and non-invasive way.