Kidney scanning is a non-invasive imaging technique primarily used to assess the morphology, function, and blood flow status of the kidneys. This examination utilizes radioactive isotopes or ultrasound technology to accurately measure renal filtration rate, excretory function, and structural abnormalities. Clinically, it is commonly used for diagnosing renal artery stenosis, kidney stones, renal tumors, or evaluating the progression of chronic kidney disease.
Unlike traditional blood tests, kidney scanning provides real-time dynamic images, assisting physicians in determining functional differences across various parts of the kidney. This technology combines anatomical and physiological information, making it an essential tool for diagnosing and monitoring kidney diseases.
There are three main categories: nuclear medicine renal dynamic scans, computed tomography (CT), and ultrasound examinations. Nuclear medicine tests use radioactive tracers, which are tracked through intravenous injection to observe their metabolism within the kidneys. Tracers such as Technetium-99m DMSA specifically bind to renal cortical cells to evaluate kidney structure, while Technetium-99m MAG3 is used to observe renal blood flow and excretory function.
CT scans generate three-dimensional images through X-ray tomography, and with contrast agent injection, can reveal renal vascular stenosis or tumor locations. Ultrasound utilizes sound wave reflection principles, with no radiation exposure risk, suitable for assessing kidney size, cysts, or stone locations. Different techniques can be used alone or in combination based on clinical needs.
This examination is also suitable for long-term monitoring of glomerular filtration rate changes in chronic kidney disease patients or evaluating treatment responses after renal angiography.
Nuclear medicine scans require fasting for 4 hours before the procedure, followed by continuous imaging after intravenous injection of radioactive tracers, with a total examination time of about 30 minutes to 2 hours. CT scans usually require oral or intravenous contrast agents, taking about 15 minutes. Ultrasound requires no special preparation, simply scanning the abdominal area with a sensor.
The radioactive dose is adjusted based on patient weight and the type of examination, generally about 3-5 mCi for adults. Special populations such as children or pregnant women need dose adjustments or alternative techniques. Post-examination, drinking plenty of water is recommended to accelerate the metabolism of radioactive substances.
Nuclear medicine scans can distinguish reversible and irreversible renal functional impairments, which is valuable for treatment decision-making. CT scans have high-resolution advantages in vascular structure visualization.
Nuclear medicine procedures may cause allergic reactions, with about 0.5% of patients experiencing mild itching or rash from the radioactive tracers. Long-term cumulative radiation exposure could theoretically increase cancer risk, but the dose from a single scan is below natural background radiation levels.
Contrast agents used in CT scans may lead to renal function deterioration, especially in patients with existing renal failure, requiring cautious use. Ultrasound has the lowest risk but results can be affected by patient body habitus or intestinal gas interference.
Before the examination, inform the doctor of any allergies or renal function abnormalities; adjustments may be necessary. Diabetic patients should check blood glucose levels beforehand, as hyperglycemia may affect the metabolism of radioactive agents.
Radioactive tracers may interfere with other concurrent nuclear medicine tests, requiring at least 48 hours between procedures. Patients taking biguanide antihyperglycemic drugs should avoid immediate use after CT contrast agent procedures to prevent metabolic disturbances.
Long-term use of diuretics may affect renal blood flow scan results; it is recommended to discontinue related medications 3 days before the scan. When combined with anticoagulants, caution is advised as contrast agents may increase bleeding risk.
Clinical studies show that nuclear medicine renal blood flow scans have an accuracy rate of over 85% in diagnosing renal artery stenosis, outperforming traditional urine tests. For patients with recurrent urinary tract infections, ultrasound scans can detect hidden stones with a success rate of up to 90%.
Multicenter studies confirm that combining CT and nuclear medicine scans can improve the accuracy of differentiating benign and malignant renal tumors. In transplant kidney function assessment, the correlation between scan results and biopsy findings exceeds 0.85.
If patients cannot undergo radioactive procedures, magnetic resonance imaging (MRI) can be used to evaluate renal vessels and tissue structures. Ultrasound can serve as an initial screening tool but cannot quantify glomerular filtration rate.
Serum creatinine clearance measurement, although non-invasive, only provides overall renal function indicators. Urinalysis can assist in diagnosing infections or stones but cannot display tissue functional differences.
What preparations are needed before a kidney scan? Is fasting or medication adjustment required?
Before a kidney scan, fasting for 4 to 6 hours is usually required, and intake of caffeinated beverages should be avoided. If taking diuretics or other cardiovascular medications, inform medical staff in advance, as they may need to be temporarily stopped or dosage adjusted. Women who are pregnant or may be pregnant should inform the staff beforehand to avoid radiation risks.
Will the procedure cause pain or discomfort? Is there any long-term harm to the body?
The procedure itself is painless; only the injection of radioactive tracers may cause a slight prick. The radiation dose used is extremely low, with minimal short-term effects on the body, but caution is advised for those with renal impairment, and the doctor will evaluate risks accordingly. Long-term, a single scan does not pose significant health hazards.
Are there any activity restrictions after the scan? When can normal diet resume?
Post-scan, no special rest is usually necessary, and normal activities can be resumed immediately. To accelerate the metabolism of the imaging agents, drinking plenty of water is recommended, and contact with others, especially pregnant women and children, should be minimized for about 6 to 8 hours. Normal diet can be resumed immediately after the scan without restrictions.
What factors affect the accuracy of kidney scans? How can the reliability of results be improved?
The accuracy may be influenced by the patient's renal function, bladder filling, or metabolic rate. To improve accuracy, strict adherence to fasting instructions, avoiding vigorous exercise before the scan, and remaining lying still during the procedure are essential. For patients with diabetes or autonomic nervous system dysfunction, the radiotracer dose or scan timing may be adjusted by the physician.
If the results are abnormal, what are the typical subsequent treatment options?
If renal blood flow or excretory function is impaired, further angiography or renal artery ultrasound may be recommended to confirm blood flow obstruction. Treatment options depend on the severity of the lesion and may include medication to control blood pressure, surgical interventions to improve blood flow, or regular follow-up. Complex cases may require multidisciplinary planning for treatment.
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