A renal scan, AKA renal scintigraphy, renal imaging, renal test, or a renogram, involves the introduction of a radioactive material (radioisotope) to examine and assess a patient’s kidneys and review their functionality.
The scan is referred to as a nuclear medicine examination, and the procedure is one of the various methods used to radiographically identify the anatomy, pathology and physiology of the kidneys.
The procedure works differently from a standard x-ray in that with ordinary x-ray examinations, an image is made by passing x-rays through the patient’s body. However, with renal scanning, a trace amount of radioisotope is injected via a vein in the patient’s arm. The category of the said isotope used may vary depending on the study being performed.
The radioisotope will filter through the bloodstream, and the scan will be performed approximately two hours later. The camera and imaging techniques used in nuclear medicine include the gamma camera and single-photon emission-computed tomography (SPECT)
The gamma camera detects radioactive energy that is emitted from the patient’s body and converts it into an image. The camera itself does not emit radiation but instead detects radioactive energy that is emitted from the patient’s body and hence converts it into an image.
The gamma camera (scintillation camera) is composed of radiation detectors called gamma camera heads attached to a circular shaped gantry. The patient lies between two parallel camera heads that are positioned above and below the examination table. SPECT involves rotation of the gamma camera heads around the patient’s body, which allows for a three-dimensional image to be produced.
The gamma camera has the ability to scan the kidney area, track the radioisotope and measure how the kidneys process the contrast. The camera works in conjunction with a computer to generate images. These images methodically explain the structure and functioning of the kidneys, based on how they interact with the radioisotope.
The scan is non-invasive and usually performed on an outpatient basis. Unlike other imaging techniques, nuclear medicine will focus on the physiological process within the body, such as rates of metabolism, instead of merely showing anatomical structure. An area of greater intensity is called a “hot spot,” where a large amount of an isotope has accumulated that indicates a high level of activity.
The scan provides information that other tests such as ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) are not able to offer.
A renal scan is used to measure function of the kidneys, including blood flow problems in the renal arteries. Tumors or cysts, as well as pockets of infection (abscesses) are also clearly visualised.