Kidney Radionuclide Scan
Definition
A kidney radionuclide scan, also called a kidney scan or renal scan, is a diagnostic imaging test that involves administering a small amount of radionuclide, also called a radioactive tracer, into the body and then imaging the kidneys with a gamma camera. The images obtained can help in the diagnosis and treatment of various kidney diseases and conditions.
Purpose
While many tests—such as x rays, ultrasounds, or computed tomography (CT scans)—can reveal the structure of the kidneys, the kidney radionuclide scan is unique in that it also reveals how the kidneys are functioning. Candidates for a kidney scan may include patients who have acute or chronic renal failure, obstruction in their urinary system, renal artery stenosis, kidney transplant, trauma to the kidney, reflux nephropathy, renal vascular disorders and/or hypertension, or congenital abnormalities.
Precautions
A kidney scan requires the use of a radioactive material; therefore, patients who are pregnant or suspect they may be pregnant are cautioned not to have the test unless the benefits outweigh the risks. Women should inform their doctor if they are breast feeding. The doctor will recommend the woman stop breast feeding for a specified period of time, depending on the particular tracer and dose used.
Description
Kidney scans are performed either in a hospital nuclear medicine department or in an outpatient radiology or nuclear medicine facility. The patient is positioned in front of, or under, a gamma camera—a special piece of equipment that detects the radiation emitted from the body and produces an image. An intravenous injection of the radionuclide is administered. Immediately after the injection imaging begins, and, in most studies, the flow of blood to each kidney is evaluated. Serial images of the kidneys are obtained over a specified period of time, depending upon the particular radiopharmaceutical used. Kidney scans may be performed to determine the rate at which the kidneys are filtering a patient's blood. These studies use a radiopharmaceutical called technetium DTPA (Tc99m DTPA). This radiopharmaceutical also can identify obstruction in the renal collecting system. To
establish the function of the renal tubules, the radiopharmaceutical Technetium DMSA (Tc99m DMSA) is used.
A kidney scan ranges from 45 minutes to three hours in length, depending upon the goals of the test, but the test typically takes about an hour to an hour and a half. It is important to understand that kidney scans can reveal an abnormality, but they do not always identify the specific problem. They are very useful in providing information about how the various parts of the kidneys function, which, in turn, can assist in making a diagnosis.
Typically, posterior images are obtained but images are also obtained at oblique angles. If indicated, the patient may be positioned so that mobility of the kidney is demonstrated by sitting up or lying down for the images. If obstruction or renal function is being evaluated, a diuretic (drug to induce urination), such as Lasix, may be injected. If hypertension or renal artery sterosis is being evaluated, Captopril or Enalapril (ACE inhibitors) may be injected.
