What are the prerequisites for having Iodine-131 therapy done? Endocrine specialists generally refer patients for these treatments. All women who…Read more
A nuclear medicine renal scan is used to assess blood flow, function and drainage of the kidneys. The radio-isotope, 99m-Tc, is bound to either DTPA (diethylene triamine pentaacetic acid) or MAG3 (mercaptoacetyletriglycine) to form the radiopharmaceutical. The radiopharmaceutical is then injected into a vein and enters the kidneys. The radioactive component of the radiopharmaceutical emits gamma rays, which allows us to image the kidneys using a gamma camera. For indications such as renal tract obstruction, often a loop diuretic (frusemide) is administered. For renovascular hypertension, a short-acting angiotensin-converting enzyme inhibitor, such as captopril, is administered.
Nuclear medicine renal scanning is carried out to assess the percentage each kidney contributes to the total renal function. A DTPA or MAG3 scan may also be done to evaluate:
For renovascular hypertension, the patient needs to be well hydrated. Some institutions require patients to also fast 4 hours before the scan to ensure the oral captopril administered is absorbed quickly.
Patients on angiotensin II receptor blocker or angiotensin-converting enzyme inhibitors should cease their medications before the test, as a captopril challenge is involved in the test. Long-acting agents (such as perindopril) and short-acting agents (such as captopril) should be ceased 4–7 days and 3 days before the test, respectively.
Furthermore, it is recommended that long-term diuretics are ceased 1–2 days before the test if clinically safe. Their use may lead to volume depletion and a consequent false negative result. Please discuss this with the nuclear medicine specialist.
Although not always essential, some radioisotope scans may require correlation with a renal ultrasound scan or other anatomical imaging techniques (e.g. CT) in assessing:
There are no known associated risks; however, the patient will be receiving a dose of radiation (See InsideRadiology: Radiation risk of medical imaging for adults and children).
Captopril and diuretics administered may result in hypotension. In general, if patients are well hydrated, this is unlikely. All patients will have an intravenous cannula inserted during the scan and can be adequately fluid resuscitated should this occur.
It is recommended that patients remain well hydrated after the test, as the effects of diuretics, if administered, may persist.
Nuclear medicine scanning is the ideal investigation for renal function assessment. Ultrasound, CT or MRI are better for structural assessment (e.g. renal cortical thickness, parenchymal pathology and obstruction). A renal DMSA scan can be used to assess the ‘amount’ of functional renal tissue compared with non-functioning scars.
Page last modified on 24/8/2018.
RANZCR® is not aware that any person intends to act or rely upon the opinions, advices or information contained in this publication or of the manner in which it might be possible to do so. It issues no invitation to any person to act or rely upon such opinions, advices or information or any of them and it accepts no responsibility for any of them.
RANZCR® intends by this statement to exclude liability for any such opinions, advices or information. The content of this publication is not intended as a substitute for medical advice. It is designed to support, not replace, the relationship that exists between a patient and his/her doctor. Some of the tests and procedures included in this publication may not be available at all radiology providers.
RANZCR® recommends that any specific questions regarding any procedure be discussed with a person's family doctor or medical specialist. Whilst every effort is made to ensure the accuracy of the information contained in this publication, RANZCR®, its Board, officers and employees assume no responsibility for its content, use, or interpretation. Each person should rely on their own inquires before making decisions that touch their own interests.