Renal scintigraphy is a well-established nuclear medicine examination method. It is used primarily for the side-by-side assessment of the function of the kidneys as well as the urinary tract organs of the genitourinary system. This is made possible by the use of a very well tolerated radioactive substance, which is injected into the patient: By recording its excretion through the kidneys by a gamma camera, kidney function can be reliably checked without invasive intervention in the body.
What is renal scintigraphy?
Renal scintigraphy is a well-established nuclear medicine examination method. It is primarily used for the side-by-side assessment of the function of the kidneys as well as the urinary tract organs of the genitourinary system. Scintigraphy of the kidneys belongs to the field of nuclear medicine and is an informative diagnostic supplement to classical examinations such as sonography (ultrasound) and special blood tests. Kidney function is detected by a radioactive substance, which is usually injected into the patient’s vein in a small dose. The tracer used to track the uptake and excretion of fluid by the kidneys is in most cases technetium, a chemical element. Its natural radiation makes it possible, with the help of the gamma camera, to convert the course of the fluid enriched with this substance in the area of the kidneys and the urinary system into meaningful images. These images are called scintigrams. In addition, using appropriate software, the performance of the kidneys is also expressed as a percentage and compared with the specified standard values. In contrast to laboratory analysis of the relevant blood values, renal scintigraphy can show the function of the two kidneys separately. Nevertheless, to round out the diagnosis, in many cases the scintigraphy is combined with an examination of the kidney values in the blood.
Function, effect, and goals
With renal scintigraphy, nuclear medicine has an effective tool if one wishes to examine, in a side-by-side manner, the blood flow to both kidneys, their functional capacity (renal clearance) and, above all, their performance with regard to excretion, i.e., the outflow of urine into the bladder. Pathological processes such as tumors or inflammations in the area of the renal pelvis and the ureters as well as urinary outflow disorders of various causes can be detected in this way by means of non-invasive diagnostics. Renal scintigraphy is also suitable for depicting possible consequences of high blood pressure, such as the relevant narrowing of renal arteries. It is also used for special questions – for example, with regard to the success of a kidney transplant or an operation in the field of urology, as well as for small children with malformations in the area of the urinary organs. Around chemotherapy or radiotherapy, scintigraphy can be used to monitor the functional performance of the kidneys without an invasive procedure. All this is made possible by the administration of a small amount of a radioactive and renal tracer, which is usually applied into the arm vein. No special preparation for this examination is necessary. Only certain X-ray examinations should be avoided in the last two days before nuclear medicine diagnostics, since the contrast medium used can distort the significance of the scintigraphy. If damage due to high pressure is to be diagnosed, blood pressure medication may also have to be discontinued after consultation with the physician. However, it is important to drink enough in the run-up to the examination – especially in the last 30 minutes beforehand. In this way, a good accumulation of the tracer in the kidney tissue and sufficient excretion can be achieved. The flow of urine can also be increased by administering diuretics shortly before the examination. Images are taken in the supine position. The gamma camera records the physiological processes in the kidney and urinary organs over a period of about 30 to 40 minutes. Due to the rapid excretion of the radioactive tracer, it is possible in this relatively short time to obtain a comprehensive picture with regard to the individual problem of the kidney scintigraphy performed.Not infrequently, the high informative value of scintigraphy can already detect disease patterns before these become apparent via changes in blood values in laboratory diagnostics.
Risks, side effects, and hazards
Like all other nuclear medicine examination methods, renal scintigraphy causes anxiety in many patients because of the radioactive drug that is injected into the arm vein. However, this is unfounded because the radiation exposure caused by the tracer is low and within the range of a classic X-ray examination, such as of the lungs. In addition, the radioactivity quickly leaves the body through natural excretion via the kidneys or urinary tract. This process can be further supported by consistent drinking after the examination. A relative contraindication – i.e. the benefit and urgency of the examination must be carefully weighed up by the physician – exists only around pregnancy and breastfeeding. Breastfeeding mothers are advised by the physician to pump and discard breast milk for 48 hours because of the radionuclide administered. In addition, patients should minimize contact with pregnant women or young children for about one day following a renal scintigraphy – as after any nuclear medicine examination. Also, an intolerance reaction to the injected tracer is usually not to be expected. Compared to contrast media used in CT (computer tomography), for example, technetium can usually be used without hesitation even in patients with a high allergy potential. The imaging itself through the gamma camera is absolutely painless. There are no restrictions after renal scintigraphy, so the patient can go about his or her personal or professional obligations as normal immediately after the examination.
