This is a useful test to get an accurate measurement of how well the kidneys are working (known as the Glomerular Filtration Rate or GFR). It is used when patients have known kidney problems, are on medication that may affect the kidneys or when they are going to have medicine that relies on the kidneys removing the waste from the body (eg chemotherapy).
Before the test, the patient must not take any caffeine (such as tea, coffee and cola) for 12 hours nor any alcohol for 24 hours. It is important that patients drink other fluids instead, before and during the test. Patients may eat a light breakfast and lunch on the day of the test, but we ask that they do not have too much protein, for example meat or cheese. This test is carried out using just blood samples and there is no need for urine samples or any imaging.
On arrival, the patient is given an injection in the arm of a very small amount of radioactivity. Blood tests are taken two, three and four hours later to see how quickly the radioactivity is being removed from the blood.
The patient can leave the department between the injection and the blood tests or they can wait in our waiting room. After the last blood test, the patient is able to go home. The injections feel similar to a blood test and have no side effects. The results of the test will be calculated and a written report will be sent to the referring doctor.