After intravenous injection of a small amount of radioactive material, a special camera records the radiotracer as it circulates through the kidneys and ureters. Data obtained by the camera can provide an image of kidney structure, and can also be recorded by a computer and analyzed to assess kidney function and blood flow. Different types of renal scans, using various radiotracers, are performed depending on what information is needed; often several types are done in succession.
Purpose of the Kidney Scan
- To evaluate kidney function in a more accurate manner than blood tests alone
- To detect kidney abnormalities, such as obstruction or reflux of urine back into the kidney
- To identify whether high blood pressure is caused by impaired blood flow to the kidney (renovascular hypertension)
- To detect organ rejection in a transplanted kidney
Who Performs Kidney Scan
- A physician or a nuclear medicine technician
Special Concerns about Kidney Scan
- This test is a safe alternative for people who cannot undergo intravenous pyelography due to iodine allergy or poor kidney function.
- Renal scanning should be done at least 24 hours after intravenous pyelography.
- The test should not be done in pregnant or breastfeeding women.
Before the Kidney Scan
- The procedure is explained and you are given the opportunity to ask questions.
- You will be asked to sign a consent form giving your doctor permission to do the procedure. Read the form carefully and, if anything is unclear, ask questions.
- There is usually no preparation required prior to a kidney scan.
- If you take an antihypertensive medication, ask your doctor if it should be withheld before the test.
- Good hydration is important for this test. The doctor will ask you to drink 2 or 3 glasses of water before it begins.
- You will be instructed to empty your bladder and remove all metal jewelry.
- Tell the radiologist or technologist if you have an allergy or sensitivity to latex, medications, contrast dyes or iodine.
- Tell your physician if you are pregnant or may be pregnant.
- Tell your doctor if you are taking medication for high blood pressure. It may be necessary to discontinue your medication for a period of time prior to the procedure.
- Your physician may recommend other preparations based on your overall health and medical condition.
What You Experience during Kidney Scan
- You will receive an intravenous (IV) line in your hand or arm for injection of the radionuclide.
- The examiner injects a radiotracer into a vein, usually in your arm. This material will circulate through your bloodstream to the kidneys. (Other than the minor discomfort of this injection, the procedure is painless.)
- You may experience brief, mild nausea and flushing after the radiotracer enters your bloodstream.
- You will be asked to sit or lie down on a table, depending on the type of scan to be done. You must remain still throughout the procedure, which may cause some numbness or stiffness. (Ask the doctor if a pillow or pads can be placed on the table for your comfort.)
- A large scanning camera is passed over the kidney area at various intervals, recording the gamma rays emitted by the radiotracer. There may be a break of several hours before certain scans are taken.
- If several types of scans are being performed in succession, you may need additional injections of radiotracers. In addition, some tests require scanning the kidney after the injection of an antihypertensive drug (typically captopril [Capoten]).
- Depending on what information is needed, kidney scanning may take from 45 minutes to three hours in length.
- If your kidney function is being assessed, urine collections may be performed at specified times during and/or after the scan.
Risks and Complications of Kidney Scan
- The trace amounts of radioactive material used in this test are not associated with any significant risks or complications.
- In rare cases, infection may develop at the injection site. Inform your doctor of any redness or swelling.
After the Kidney Scan
- Empty your bladder immediately after the procedure is finished. Most of the radioactive material is excreted in the urine within 6 to 24 hours. Drinking plenty of fluids facilitates this process.
- Most patients may go home the same day of the test and resume their normal activities. Some may require overnight hospitalization.
- Blood may collect and clot under the skin (hematoma) at the injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- A physician will examine the recorded images and other test data for any evidence of kidney disease or other abnormalities.
- If a definitive diagnosis can be made, appropriate treatment will be initiated.
- Abnormal results may also necessitate additional tests, such as intravenous pyelography, renal arteriography, or an abdominal CT scan.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media