Kidneys are an organ that requires a thorough and often multi-stage diagnosis. At the same time, a variety of instrumental methods are used. Nefrosintcinigrafiya allows you to get data not so much the state of the body, but about its functionality.
Nephroscintigraphy of the kidneys - what is it?
Nephroscintigraphy is one of the methods of radiation diagnosis. Known for a long time, but as an instrumental research method was used only in the second half of the 20 th century.
The method involves the introduction of special drugs that include a radionuclide tag. The advantage of this solution is the lack of pharmacological effect of the drug itself, since the action is based not on the composition of the drug, but on the radiation of the radionuclide.
As it turned out during the development of radiography methods, healthy and damaged tissues differently retain radionuclides. Fix and visualize this distribution using a gamma camera. Nephroscintigrams reflect the process of radionuclide intake
into the kidney tissues and its passage through the ureters. Thus, a dynamic picture of the processes occurring in the organ is obtained.
Nephroscintigraphy is one of the safest methods of investigation, since the radioactivity of drugs is negligible and does not affect the patient's condition in any way. Moreover, the introduced RFP affects only the organ under investigation.
So, for the examination of the kidneys apply 3 known drugs:
- sodium iodiphippurate - allows you to assess glomerular filtration, tubular secretion, the condition of the parenchyma. At the same time, the drug is considered to be the most radiotoxic for today, therefore, when examining children, its more recent modifications are used;
- pentatech 99mTc is one of the glomerulotropic compounds used in the study of glomerular filtration. Less toxic;
- colloid solutions, labeled with technetium - are more often used in the diagnosis of bone tissue, but are used in radioisotope nephroscintigraphy, since they are characterized by minimal radiotoxicity.
A dose of drugs is calculated by the doctor before each examination for each patient.
Neutroscintigraphy is indispensable in the early stages of disease, when the state of the kidney tissue has not yet undergone significant changes, while functional disorders are already manifesting. There are several types of research: tasks and opportunities are different, therefore, with different indicators, different types of scintigraphy are prescribed.
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Static and dynamic methods are primarily distinguished:
- Static nephroscintigraphy - provides information about structural changes: organ size, shape, placement, changes in parenchyma structure due to different rate of absorption of the drug by healthy and damaged tissue, and so on. The examination lasts from 30 minutes to 3 hours 15-60 minutes after the administration of the RFP.
Dynamic and static nephroscintigraphy
- Dynamic - involves the gradual introduction of the drug and kidney scanning at intervals to obtain a complete picture of the progress of the radionuclide with blood and urine before the drug enters the bladder. Thus, information is received on the state of the blood vessels of the kidney, the fullness of the blood supply, the functionality of the kidney tissue, and so on. The study allows you to assess the efficiency of the body, but does not clearly indicate the cause of the disease. There are 2 types of dynamic examination. Radioisotope renography is based on the study of active tubular secretion. The drug enters the kidneys, is absorbed by the tubules, and is excreted into the urinary bladder with urine. When examining RFP is administered intravenously. The signal is recorded continuously.
As a result of the renography, a curve is obtained - a rheogram consisting of 3 sections: vascular - the distribution of the radionuclide in the vascular bed, secretion - accumulation of RFP in the kidney tissue, and evacuation, which reflects the process of excretion of the drug.
Renography is not universal: for example, a renography registers a signal not only from a drug in the kidney, but also from the RFP, which has appeared in the soft tissues around the organ. Precisely to distinguish a share of participation secretory and excretornogo a stage it is impossible, therefore division of a curve on sites remains approximate. It is impossible to accurately assess the degree of withdrawal of the drug, again, because part of the RFP is in the intercellular space.
Actually, dynamic nephroscintigraphy - in fact, differs from conventional renography much more advanced equipment. The principle is the same: the drug injected into the vein gets into the kidneys, absorbed by the tubules and excreted. One or several gamma detectors register signals. However, the use of modern sensors allows you to change the zones of interest during the survey. The received data are transferred to the computer memory, where a special program performs several renograms and visualizes the functional state of the kidney.
In comparison with the traditional method, dynamic nephroscintigraphy is more informative: there are no position errors, since the camera captures the entire possible area of the organ placement, it is possible to separate the signal of the drug found in the perineal tissue from the RFP in the kidney, it is possible to separate data on the secretory and excretory functions, and so on.
The accuracy of the method is also significantly higher: if renography allows one to determine the difference in the functionality of the kidneys only at 15% of the deviation, then dynamic scintigraphy does the same with a difference in state of only 5%.
Purpose and indications for
The determination of the degree of kidney function greatly contributes to the establishment of an accurate diagnosis, especially in the initial stages of ailments of unknown origin. It is often prescribed dynamic scintigraphy, because it is more informative.
Static nephroscintigraphy is prescribed:
- in cases of abnormal anatomical organ placement;
- for suspected malformations;
- with apology of the kidney - pyelonephritis, acute and chronic insufficiency, organ trauma.
Dynamic scintigraphy is used:
- for deviations in functionality of any severity. When determining the working state of an organ, this is indeed a universal method;
- when abnormalities are detected in kidney development;
- for suspected metastases in the urinary system;
- when examining cysts and any other neoplasms, including malignant ones;
- before the removal operation to assess the condition of the second organ;
- when examining the kidney before organ-preserving operations.
Preparation for research and contraindications
The examination takes from 45 minutes to 3 hours - an average of one and a half hours. It is carried out on an outpatient basis. Special preparation is not required here, however it is desirable, in order to avoid side effects, to perform it not on an empty stomach.
To improve the quality of the scintigram, in some cases it is required to drink a special liquid.
Although the procedure is safe enough, there are a number of limitations:
- pregnancy - RFP still refers to radiotoxic materials, and therefore pregnant women are prescribed this examination only in an emergency;
- breast-feeding - you can carry out the procedure, but since the drug is removed from the human body during the day, at this time the milk must be replaced with a mixture;
- treatment with chemotherapy or radiotherapy - a certain time must pass before the scintigraphy: 3 weeks after chemotherapy and 3 months after irradiation.
If any of the methods of radiation diagnosis has already been applied, it is also necessary to maintain a pause between the procedures for at least 3 weeks.
How to diagnose
The main equipment for the procedure is a gamma camera - one or more. It captures the gamma rays emitted by the RFP, and on the basis of signals forms a visual image.
The device is contained in a specially equipped room in the nuclear medicine department:
- Before examining, remove all metal objects in the study area. If necessary, drink a special liquid.
- The patient is located in front of or under the gamma camera on the diagnostic table of a gamma tomograph. Staff during the study is in the next room.
- The patient is intravenously injected with RFP.Scanning starts immediately, which allows you to assess the blood flow in the kidneys, and to obtain data on blood circulation in each kidney separately.
- During the procedure, it is forbidden to talk. You can not arbitrarily move.
- As a rule, when scanning the patient is in a lying position, that is, receive a direct projection. But to assess the mobility of the kidney requires an image at an angle. For this, the patient is offered to sit down or change the position during the scan.
- Possible introduction of additional drugs. So, when studying obstruction, a diuretic is administered. If the renal artery is examined for suspected stenosis, hypotensive drugs, captopril, enalapril, are administered.
Consequences and complications of
The preparations used in the scanning process create a minimal radiation load, unlike the substances used in computed tomography. A survey of this kind can take place almost every other day. RFP disintegrates within 24 hours and is excreted from the body with urine. The only recommendation is to drink more liquid after the procedure.
No complications are recorded.
The only drawback of the method is the high cost of equipment. Not every private or public clinic has the opportunity to acquire modern technology.
Nephroscintigraphy is a safe and very informative method of examination, which allows obtaining not only data on the shape and structure of the kidney, but also to assess its working state and functionality.
On the video about the method of scintigraphy: