Renal transplantation is an effective means of regaining renal function in end-stage renal disease and can lead to a significant improvement in quality of life.1 The gap between supply and demand of donor kidneys continues to increase due to the prevalence of end-stage renal disease and its underlying comorbidities. To address this gap, the concept of expanded criteria donors (ECD) has been proposed to enhance donor supply and reduce waiting time for kidney transplant recipients.1 However, poorer outcomes, including decreased renal graft survival rates and an increased incidence of delayed graft function (DGF), have been observed in end-stage renal disease patients receiving kidneys from ECD compared with standard criteria donors (SCD).2 Since both short- and long-term survival of renal grafts are affected by DGF, its early identification and management is critical.3,4 Biopsy is the gold standard for diagnosis of DGF but is associated with risk of complications such as bleeding, arteriovenous fistula formation, renal graft damage, and infection. In recent years, novel imaging modalities and techniques, including in nuclear medicine, have been introduced for the investigation of renal graft function, pathology, and DGF.5

Complications after renal transplantation can be broadly categorized as non-vascular and vascular. Non-vascular complications may be surgical or medical in etiology and require diagnosis within a defined timeframe from surgery.6 Renal scintigraphy is considered one of the main quantitative and qualitative nuclear imaging techniques for evaluating the perfusion and function of renal grafts, particularly in patients suspected of having post-transplantation complications.7 Two main radiotracers used for the evaluation of renal transplantation are Technetium-99 m diethylene triamine pentaacetic acid (Tc-99 m DTPA) and Technetium-99 m mercaptoacetyltriglycine (Tc-99 m MAG3). Glomerular filtration is the primary mode of clearance of Tc-99 m DTPA, making it useful for assessing the glomerular filtration rate (GFR). In contrast, Tc-99 m MAG3 is secreted by the proximal renal tubules which lends itself to higher-quality imaging.8 Post-transplant renal scars can be diagnosed with high sensitivity using Technetium-99 m dimercaptosuccinic acid (Tc-99 m DMSA) in combination with single-photon emission computed tomography (SPECT).9

Nevertheless, current imaging technologies are not without limitations in the field of renal transplantation. One of the most fundamental limitations is the inability to classify types of renal graft rejection or to differentiate graft rejection from other causes of renal failure.10 Given the need to monitor renal function and complications in post-transplant patients, as well as the risks of renal biopsy and the emergence of new imaging options, reviewing the literature and synthesizing evidence from high-quality studies to provide an evidence-based summary of renal graft imaging is essential. Therefore, in this narrative review, we aimed to provide an updated overview of renal graft imaging and recent advancements in the field.