Elsevier

Seminars in Nuclear Medicine

Volume 45, Issue 5, September 2015, Pages 428-439
Seminars in Nuclear Medicine

Pitfalls and Limitations of Radionuclide Renal Imaging in Adults

https://doi.org/10.1053/j.semnuclmed.2015.02.008Get rights and content

To understand pitfalls and limitations in adult renography, it is necessary to understand firstly the physiology of the kidney, especially the magnitude and control of renal blood flow, glomerular filtration rate and tubular fluid flow rate, and secondly the pharmacokinetics and renal handling of the three most often used tracers, Tc-99m-mercaptoacetyltriglycine (MAG3), Tc-99m-diethylene triamine pentaacetic acid (DTPA) and Tc-99m-dimercaptosuccinic acid (DMSA). The kidneys may be imaged dynamically with Tc-99m-MAG3 or Tc-99m-DTPA, with or without diuretic challenge, or by static imaging with Tc-99m-DMSA. Protocols are different according to whether the kidney is native or transplanted. Quantitative analysis of dynamic data includes measurement of renal vascularity (important for the transplanted kidney), absolute tracer clearance rates, differential renal function (DRF) and response to diuretic challenge. Static image reveals functional renal parenchymal damage, both focal and global, is useful in the clinical management of obstructive uropathy, renal stone disease and hypertension (under angiotensin converting enzyme inhibition), and is the preferred technique for determining DRF. Diagnosis based on morphological appearances is important in transplant management. Even though nuclear medicine is now in the era of hybrid imaging, renal imaging remains an important subspecialty in nuclear medicine and requires a sound basing in applied physiology, the classical supporting discipline of nuclear medicine.

Section snippets

Applied Physiology of the Kidney

To understand the pitfalls and limitations of renal imaging with radionuclides, it is essential to understand the relevant physiology of the kidney.

For a standard-sized adult, renal blood flow is approximately 500 mL/min per kidney, which is approximately 20% of cardiac output. Renal perfusion is 300-350 mL/min/100 g. The blood volume of a single kidney is approximately 50 ml. Renal plasma flow (RPF) is 250-300 mL/min per kidney. Glomerular filtration rate (GFR) is 50-60 mL/min per kidney, so

Pharmacokinetics of Radiopharmaceuticals for Imaging the Kidneys

For dynamic imaging:

  • Tc-99m-diethylene triamine pentaacetic acid (DTPA) (Pentatate; 492 Da)

  • Tc-99m-MAG3 (Mertiatide; 350 Da)

For static imaging:

  • Tc-99m-dimercaptosuccinic acid (DMSA) (Succimer; 281 Da)

Tc-99m-DTPA, like inulin, circulates in blood with negligible binding to plasma proteins and does not penetrate red cells. It is freely filtered at the glomerulus. As a small hydrophilic molecule, Tc-99m-DTPA crosses capillary endothelium throughout the body by passive diffusion between the

Native Kidneys

The patient should be well hydrated and have recently voided. The supine position, with the gamma camera under the imaging couch, is the most comfortable for the patient. Some departments image patients in a semi-recumbent or even sitting position to promote drainage from the renal collecting systems but this is an awkward position for the patient to maintain and is therefore prone to movement artefact. In any event, it should be routine practice to take the patient from the imaging couch at

Indications for Renal Scintigraphy in Adults

A useful general rule in deciding between dynamic and static renal imaging in a particular clinical scenario is to choose DMSA, which is best for relative function and focal cortical loss, unless information is required of renal blood flow and outflow tract drainage, or both.

Dynamic Renal Imaging

It is helpful to approach the study by interpreting the 3 phases of the renogram, in order.

Conclusion

Renal imaging remains an important subspecialty in nuclear medicine. In the era of hybrid imaging in which anatomy is all important, a proper understanding of renal imaging, including an appreciation of pitfalls and limitations, requires a sound basing in applied physiology, the classical benchmark of nuclear medicine.

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