SPECT and PET Radiotracers in Renal Imaging

Diuretic scintigraphy includes single-photon emitting radiotracers for planar and single photon emission computed tomography (SPECT) imaging as well as agents for positron emission tomography (PET). These radiotracers provide split-renal functional parameters, including glomerular filtration rate, effective renal plasma flow, tubular function, and/or renal blood flow. Beyond measuring kidney function, the tracer principle also allows for the assessment of various pathophysiological processes in the renal parenchyma, for example ongoing inflammation, activation of angiotensin II type 1 receptor in patients with renovascular hypertension, deterioration of mitochondrial complex I following acute or chronic kidney injury, or characterization of indeterminate renal masses. Providing a whole-body read-out, PET also enables the assessment of kidney-organ interactions, for example cardiorenal crosstalk after primary cardiac injury. This manuscript provides an overview of established clinical applications for single-photon-emitting and PET radiotracers for renal radionuclide imaging. Future perspectives in the field will also be highlighted, such as introduction of PET-guided strategies for drug dose optimization and the recent introduction of radiotracers targeting fibroblast activation protein inhibition, which may allow differentiation between acute inflammatory vs chronic fibrosis in the kidneys.