Glomerular Filtration Rate (GFR) Renal Study

General Information | Scheduling, Insurance and Preparation | What to Expect

General information General Information

About Nuclear Medicine

Nuclear medicine exams image bodily function rather than anatomy. They can be useful in finding problems that are not obvious by looking at the structure of an organ or tissue. This is done with the use of small amounts of radioactive materials, also known as tracers. Each tracer is designed to be attracted to specific organs or types of body tissue. Special cameras that can map the distribution of the radioactive tracer create images which are studied by radiologists.

Nuclear medicine scans are very safe. Nuclear medicine has been used in newborns and children for more than four decades and even longer in adults. There are no known long-term adverse effects from such low-dose exams.

About Glomerular Filtration Rate Renal Studies

A glomerular filtration rate (GFR) renal study, also known as a Glofil test, is a nuclear medicine exam in which the patient receives an injection of a radioactive tracer followed by blood sampling. The amount of radioactive material circulating in the blood is measured at specific time intervals to check the filtering ability of the kidneys.

GFR renal studies may be used to accurately check the kidney function of patients undergoing treatment for kidney disease such as following a kidney transplant.

Risks Involved in a Glomerular Filtration Rate Renal Study

The risks involved in a GFR renal study are minimal. They include the following:

  • Radiation exposure; however, a very small amount of radioactive material is used and the radiation exposure is well below the level that generally causes adverse affects.
  • Allergic reactions to the radioactive material; however, this is rare.
  • Discomfort during the IV insertion.

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Scheduling, Insurance and Preparation Scheduling, Insurance and Preparation

Exam Locations

The exam is performed at the following Radiology Imaging Associates partner hospitals in the Denver, Colorado area:

  • Porter Adventist Hospital
Call the hospital to schedule.


To schedule a glomerular filtration rate renal study, please call the hospital where the exam will be performed.

Insurance Coverage

GFR renal studies are usually covered by insurance when ordered by a physician. Check with your insurance company to be sure. Please bring your insurance card with you to your exam.

Conditions to Let Us Know About

In advance of your exam, let your scheduler, technologist, or radiologist know if any of the following circumstances apply to you (or your child):

  • Pregnant or may be pregnant
  • Breastfeeding
  • Claustrophobic
  • Iodine allergy

Preparation Guidelines

Following are the general preparation instructions for this exam. You may receive additional or differing guidelines based on your specific situation. Please contact the hospital at which you will have the exam if you have any questions.

  • You should arrive for the study as well hydrated as possible by drinking plenty of water beginning the day before.
  • You should not have any scans using iodinated contrast (x-ray dye) 24 hours prior to the exam. You should not have had any recent scans using other radioactive tracers.
  • If the patient is your child, bring any of the following items to increase his or her comfort: CDs, movies, pacifiers, special blankets, and stuffed toys.

Support for Children

If your child is having the exam, it is important that you provide emotional support for him or her before and during the procedure. If your child is old enough to understand, explain the procedure to him or her. Let him or her know that the exam won’t hurt and that he or she will have to lie very still throughout the exam. Also reassure your child that you will be able to remain in the room during the exam.

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What to Expect What to Expect

During the Exam

A nuclear medicine glomerular filtration rate renal study requires multiple sessions. Here is generally what will happen:

  1. You will complete some paper work upon arrival.
  2. You will ingest a small drink containing drops of potassium iodide to prevent your thyroid gland from taking up the tracer.
  3. An intravenous line will be started.
  4. Thirty minutes after drinking, you will be given an injection of I125 Iothalamate.
  5. A technologist will draw approximately 3 ml of blood from the intravenous line at the following time intervals after the injection:
    1. 60 minutes
    2. 3 hours

Fatty foods, caffeine, and tobacco should be avoided until the exam is completed.

After the Exam


You can return to your normal activities immediately after the exam.

Exam Results

A board-certified radiologist experienced in the interpretation of GFR renal studies will analyze the data and results from your exam. If the patient is a child, the exam data will be analyzed by a radiologist experienced in the interpretation of pediatric GFR renal studies. The results will be reported to your physician. Your physician will pass the results onto you.

During the exam, our radiologists and technologists will be happy to answer questions about the exam itself; however, they will not immediately provide you with the results of your exam.

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