Renal Scintigraphy

Static renal scintigraphy (synonym: DMSA scintigraphy) is a diagnostic procedure in nuclear medicine that is particularly important in assessing the function of the renal parenchyma after renal infarction. The procedure is a well-established method in nuclear medicine diagnostics, as it allows assessment of the location, size and function of both kidneys. The static of renal scintigraphy shows only functional renal parenchyma (kidney tissue)

Indications (areas of application)

  • Functional testing after renal infarction – after an infarction of the kidney, usually caused by an embolism (complete or incomplete occlusion of a blood vessel), there is usually an undersupply of oxygen and nutrients to the tissue, so that there is a decline of the renal parenchyma in the affected region. Static renal scintigraphy can be used to evaluate the extent to which the infarction has affected the function of the tissue. However, existing renal perfusion must be verified with additional diagnostic procedures.
  • Suspicion of missing kidney – if a kidney could not be visualized by sonography, static renal scintigraphy is a procedure of choice.
  • Ectopic kidney tissue – ectopic kidney tissue is a positional abnormality of the kidney tissue. Shape abnormalities (e.g., horseshoe kidney) can also be accurately visualized with static renal scintigraphy.
  • Degenerative kidney diseases – the use of static renal scintigraphy is indicated in degenerative kidney diseases such as cystic kidneys.
  • Diagnosis of scarring in pyelonephritis (inflammation of the renal pelvis) – after pyelonephritis, the presence of scar tissue in the kidney can be detected after about six months using static renal scintigraphy.
  • Kidney trauma – possible loss of function can be demonstrated beyond doubt.
  • Detection and functional verification of multicystic kidneys – static renal scintigraphy allows the detection of non-functional multicystic kidneys.

Contraindications

Relative contraindications

  • Lactation phase (breastfeeding phase) – mothers should discontinue breastfeeding for 48 hours to avoid risk to the child.
  • Children – when performing static renal scintigraphy, it should be noted that the examination leads to a significant radiation exposure of the gonads (testes/ovaries) and kidneys in children.
  • Repeat examination – within three months should not be repeated scintigraphy due to radiation exposure.

Absolute contraindications

  • Gravidity (pregnancy)

Before the examination

  • Medication history – due to interference with static renal scintigraphy, it must be known if any medications are taken by the patient that could affect the measurement.
  • Application of the radiopharmaceutical – via a previously placed venous access, 99m-Tc-DMSA is usually administered as a radioactive pharmaceutical. It should be noted that in children, only a significantly reduced amount of the radiopharmaceutical may be applied.

The procedure

The basic principle of static renal scintigraphy is based on the application of 99m-Tc-DMSA as a radiopharmaceutical. The activity level of the radiopharmaceutical should be adjusted to the patient’s weight. This radioactive substance is permanently stored in the tubular cells of the kidney after binding to plasma proteins (special proteins (albumen) in the blood) and is excreted by the kidney only to a small extent. Because of this, the functional assessment of the renal parenchyma can be considered very precise. Only about one third of the applied activity can be detected in the patient’s urine 24 hours after injection. To assess the function of the parenchyma, images of the kidneys are taken four hours after injection of the radiopharmaceutical. Using the “region of interest” technique, the impulses of the two kidneys examined can be determined in a side-specific manner. This makes it possible to calculate the percentage of function of each kidney. The average duration of the examination is five hours, this period including the four-hour waiting time after injection of the radiopharmaceutical 99m-Tc-DMSA. The creation of the single image takes another 20 minutes.After conventional scintigraphy, SPECT (single-photon emission computed tomography) is often performed as part of the examination to allow improved assessment of the renal cortex. It should be further noted that sources of error, such as misinjection of the radiopharmaceutical or scintigraphy performed too early, can affect the measurement results.

After the examination

No special measures are necessary after scintigraphy. The further procedure after the examination must be discussed with the attending physician.

Possible complications

  • Intravenous application of radiopharmaceutical may result in local vascular and nerve lesions (injuries).
  • Radiation exposure from the radionuclide used is rather low. Nevertheless, the theoretical risk of radiation-induced late malignancy (leukemia or carcinoma) is increased, so that a risk-benefit assessment should be performed.