Generality
Renal scintigraphy is a diagnostic examination of nuclear medicine, which allows to study in detail the anatomy and function of the kidneys, detecting any anomalies.
The preparatory rules for the exam are few and simple to follow; among these, fasting does not appear.
Depending on the topic of investigation, a renal scintigraphy can last from 30 to 120 minutes.
The risks are minimal.
Thanks to renal scintigraphy, doctors are able to recognize and evaluate conditions such as: kidney failure, cysts or kidney tumors, inflammation or kidney infections, obstructions to the renal arteries, alterations to the flow of urine inside of the kidneys, the complications of a kidney transplant, nephrovascular hypertension, hydronephrosis, etc.
Short revision of the kidneys
The urinary tract or excretory apparatus is the set of organs and anatomical structures responsible for the elimination of urine .
The main organs of the urinary tract are the kidneys .
Two in number, the kidneys reside in the abdominal cavity, on the sides of the last thoracic vertebrae and the first lumbar vertebrae; they are symmetrical and have a shape that is very reminiscent of a bean.
The most important functions of the kidneys are:
- Filter waste substances, harmful substances and foreign substances present in the blood and convert them into urine.
- Adjust the hydro-saline balance of blood.
- Adjust the acid-base balance of blood.
- Produce erythropoietin glycoprotein.
The anatomy of the kidneys is quite complex: the image below shows the main anatomical elements of a generic human kidney.
What is renal scintigraphy?
Renal scintigraphy is a diagnostic examination of nuclear medicine, which, through the venous injection of radiopharmaceuticals, allows us to accurately analyze the anatomy and function of the kidneys, and to determine whether the latter are "working" appropriately or no.
In addition to radiopharmaceuticals, performing a renal scintigraphy involves the use of a special device - the so-called gamma camera - capable of reproducing the distribution of the radiopharmaceutical in the body in images.
The camera range is connected to a computer that serves to regulate its operation.
A specialist in nuclear medicine, also called a nuclear doctor, performs renal scintigraphy and above all interprets the results.
Unlike the CT or X-ray instrument, renal scintigraphy does not emit radiation, but detects those emitted by the patient once the radiopharmaceutical has been injected.
What is nuclear medicine?
Nuclear medicine is that branch of medicine based on the use of radioactive substances (so-called radiopharmaceuticals ) for diagnostic and therapeutic purposes.
A radiopharmaceutical is an injectable medicine that contains radionuclides, or radioactive isotopes .
Once injected, radiopharmaceuticals can interact specifically with a specific biological tissue (like a normal drug) and, by virtue of their radioactive properties, they can be monitored using a special radioactivity ( gamma-camera ) instrumentation . In this way, this complex instrumentation provides very clear images of how, over time, the radiopharmaceutical is distributed within the body.
Scintigraphy is a diagnostic examination of nuclear medicine, based on the detection of radiation emitted by an organism after the administration, in the latter, of radiopharmaceuticals. These radiations, suitably processed by an ad hoc tool, allow us to investigate the location, shape, size and functionality of various organs, including the heart, thyroid, bones, brain, liver, kidneys and lungs.
In light of what has just been stated, one can understand why radionuclides are also identified with the word " tracers ".
Note : the distribution of radioactive isotopes in a certain tissue or their interaction with a given organ depends exclusively on the drug to which the aforementioned radioactive isotopes are bound. Therefore, the choice of the pharmacological preparation is of fundamental importance for the correct execution of the examination. For example, for a thyroid analysis it is necessary to use a drug that spreads specifically in this organ of the body; the same applies to the heart, kidneys, etc.
Indications
Renal scintigraphy allows not only to identify the causes of a possible malfunctioning of the kidneys, but also to clarify whether a certain treatment, applied for the treatment of some renal pathology, is having an effect or not.
Going into more detail, through renal scintigraphy doctors are able to recognize and evaluate:
- A reduction in blood supply to the kidneys;
- A state of nephrovascular hypertension, ie high blood pressure due to a narrowing of the arteries that carry blood to the kidneys;
- Cysts or kidney tumors;
- A renal abscess;
- The results of renal medical treatment;
- The outcome and complications of a kidney transplant;
- Acute or chronic renal failure;
- A kidney infection ( pyelonephritis );
- Injuries to the kidneys or related structures (eg: ureters);
- A state of obstructive uropathy;
- The hydronephrosis;
- A glomerulonephritis.
Types of renal scintigraphy
Renal scintigraphy includes 4 different techniques for studying kidney function. The techniques in question are:
- Static or cortical renal scintigraphy . Provides information related to the functioning of the cortical portion of the kidneys.
With this technique, the collection of images with the gamma camera can only take place after about 2 hours have elapsed since the administration of the radiopharmaceutical.
- Functional perfusional renal scintigraphy . It has various purposes: it shows the flow of blood inside the kidneys, detects any narrowing of the renal arteries and, finally, helps to understand how the kidneys are working.
With this technique, the collection of images with the gamma camera can take place immediately after the radiopharmaceutical injection; in general, doctors take a picture of the kidney situation every 20-30 minutes.
- Diuretic renal scintigraphy . Identify any blockages or obstructions in the urinary stream within the kidneys.
This technique involves the observation of the urine flow in the kidneys both before and after the patient's intake of a diuretic, ie a diuresis stimulant.
- Sequential renal scintigraphy with ACE inhibitors . Thanks to the use of a drug against high blood pressure (ACE inhibitor), this technique allows to understand if the hypertension present in an individual is due to a narrowing of the renal arteries.
For a correct and successful execution of sequential renal scintigraphy with ACE inhibitors, it is essential to observe the kidneys both before and after the administration of the anti-hypertensive drug.
Preparation
Renal scintigraphy does not require special preparation . In fact, the only preparatory rules that the patient must follow are:
- Communicate to the doctor who prescribes renal scintigraphy any pharmacological assumption in progress at that time, since there are medicines, some of them very widespread, capable of polluting the results of the diagnostic test in question. Among the medicines that, if used, can alter the outcome of renal scintigraphy, we note in particular: the ACE inhibitors (for the treatment of high blood pressure and some heart diseases), the beta-blockers (also for the treatment of hypertension and heart disease), diuretics and Non-Steroidal Anti-inflammatory Drugs or NSAIDs (including aspirin and ibuprofen).
Once the patient has communicated the medications he is taking, the doctor will decide what to do: for example, a possible solution is the request to temporarily interrupt the ongoing pharmacological intake and resume it only after performing the renal scintigraphy.
- Always report to the doctor who prescribes renal scintigraphy any possible allergy and pathological condition in place or in the recent past.
In the event that the patient is a woman, communicate also a possible state of pregnancy or presumed one.
- In the hours just before renal scintigraphy, drink in abundance (at least 1 liter of water) so that, at the time of the examination, the bladder is full.
- Present yourself for examination without preferably jewelery or clothing with metal parts, as these could interfere with the success of renal scintigraphy.
Is there a fast?
Unless otherwise indicated by the doctor, fasting is not among the preparatory rules. Therefore, the patient can eat as is his custom.
Procedure
First, the patient must deprive himself of all objects and clothing that could interfere with the success of renal scintigraphy; after which, it must lie down on a special sliding bed, which serves to position it between the plates of the gamma camera (see figure).
In order to be placed correctly on the couch, the patient can count on the help of a medical staff member, usually a technician from the nuclear medicine department or a general nurse.
At this point, with the patient lying down and before the introduction of the latter into the gamma camera, the nuclear doctor intervenes, who, thanks to the collaboration of a professional nurse, injects the radiopharmaceutical necessary for renal scintigraphy.
Radiopharmaceutical injection usually takes place in a vein in the arm or hand ; the radiopharmaceutical takes a few minutes to distribute itself, through the blood, to the organs being investigated, namely the kidneys.
After the time required for the radiopharmaceutical to be distributed in the kidneys, the patient can finally be introduced between the plates of the gamma camera, and the detection of radioactivity begins.
It should be pointed out that, at this point in the procedure, renal scintigraphy can vary from circumstance to circumstance, depending on its final purpose: for example, if the search for obstructions to urine flow in the kidneys is planned, the examination requires, at a given moment, the administration of a diuretic; if instead the object of diagnostic research is the narrowing of the renal arteries, the test foresees, at a certain moment, the use of an ACE inhibitor; and so on (see the statement on the types of renal scintigraphy).
During the collection of images through the gamma camera, the patient must remain immobile ; his movements, in fact, could alter the outcome of the diagnostic examination and the precision of the images.
Once the images necessary for a detailed assessment of the renal situation have been acquired, the nuclear physician declares the renal scintigraphy to be concluded and allows the extraction of the patient from the gamma camera, an extraction of which a department technician or a general nurse deals.
Once coated, the patient can immediately return home and resume his normal daily activities, unless otherwise medically indicated.
During a renal scintigraphy, the most active metabolic kidney areas accumulate so much radiopharmaceutical, while the less active ones accumulate in small quantities. The areas with the highest concentration of radiopharmaceuticals are called " hot spots ", while those with a low concentration of radiopharmaceuticals are called " cold spots ".
How long does renal scintigraphy last?
A renal scan can last from 30 minutes to 2 hours .
Its length depends on the purpose (for example, the intake of drugs during the procedure lengthens the time) and the number of images that the nuclear doctor intends to collect, to formulate an accurate diagnosis.
Recommendations to the patient immediately after the examination
Immediately after the examination, the doctor limits himself to recommending the patient to drink a lot of water, to favor the natural elimination of the radiopharmaceutical.
If the patient abides by this recommendation, he removes the radiopharmaceutical from his body within 24 hours.
What feelings does the patient feel during the procedure?
The patient may experience some sort of discomfort when inserting the needle, for radiopharmaceutical injection.
In addition, after injection, you may experience a strange metallic taste.
Patients struggling to remain immobile may feel uncomfortable after a short time; however immobility is a fundamental condition for the success of the exam.
When should the patient have to wait before returning home?
The patient may have to wait before returning home, in the event that unclear images emerge from renal scintigraphy, which require the repetition of the examination or part of it.
risks
Renal scintigraphy is a procedure that, according to the reliable opinion of doctors and experts, is safe.
However, it is good to remember that:
- It provides the patient's exposure (especially to the kidney and bladder) to a dose of harmful radiation .
Extent of risk? Fortunately, the radiation dose is minimal.
- In some subjects, the radionuclides (or radioactive isotopes) that make up radiopharmaceuticals could give rise to unpleasant allergic reactions (anaphylactic reactions).
Extent of risk? Post-renal allergic scintigraphy reactions are a very rare occurrence, involving very few patients.
- Given the relatively recent birth of nuclear medicine, the effects that the latter can have on the health of human beings in the long term are unknown.
- The needle used to inject the radiopharmaceutical may be responsible for a small wound and redness, where it is inserted.
Extent of risk? Wound and redness resolve within 24-48 hours.
Contraindications
They certainly represent a contraindication to renal scintigraphy: pregnancy, breastfeeding and failure to discontinue pharmacological treatments based on ACE inhibitors.
Results
Depending on the severity of the patient's condition, the results of renal scintigraphy may be available immediately or after a few days.
A renal scintigraphy with a clinically relevant outcome (hence from abnormal results) occurs under conditions such as: renal insufficiency (both acute and chronic), cysts or renal tumors (NB: renal scintigraphy does not distinguish the two circumstances ), kidney inflammation or infection, obstruction of the renal arteries, changes in the flow of urine inside the kidneys, complications of a kidney transplant, nephrovascular hypertension, hydronephrosis, etc.
Advantages
Renal scintigraphy provides information that is often impossible to achieve with other diagnostic procedures.
