Kidney graft rejection studies with labeled platelets and lymphocytes

Non-invasive molecular imaging of kidney diseases

In nephrology, differential diagnosis or assessment of disease activity largely relies on the analysis of glomerular filtration rate, urinary sediment, proteinuria and tissue obtained through invasive kidney biopsies. However, currently available non-invasive functional parameters, and most serum and urine biomarkers, cannot capture intrarenal molecular disease processes specifically. Moreover, although histopathological analyses of kidney biopsy samples enable the visualization of pathological morphological and molecular alterations, they only provide information about a small part of the kidney and do not allow longitudinal monitoring. These limitations not only hinder understanding of the dynamics of specific disease processes in the kidney, but also limit the targeting of treatments to active phases of disease and the development of novel targeted therapies. Molecular imaging enables non-invasive and quantitative assessment of physiological or pathological processes by combining imaging technologies with specific molecular probes. Here, we discuss current preclinical and clinical molecular imaging approaches in nephrology. Non-invasive visualization of the kidneys through molecular imaging can be used to detect and longitudinally monitor disease activity and can therefore provide companion diagnostics to guide clinical trials, as well as the safe and effective use of drugs.

Radioisotopic evaluation of renal transplants

Owing to the noninvasive nature, ready availability, and efficacy, radionuclide studies remain widely utilized following renal transplantation for monitoring changes in the functional status and detection of detrimental complications of the grafted kidney. Whereas surgical complications, including vascular occlusion, urine extravasation, drainage obstruction, hematoma, or lymphocele formation, can often be detected effectively, specification of other underlying causes of deterioration of parenchymal function, including acute tubular necrosis (ATN), various types of rejection, and cyclosporine A nephrotoxicity (CyA-NT), frequently cannot be derived independently from the findings of a study without clinical correlation. Besides imaging, plotting of renogram or time/activity curves, numerous quantitative methods have been introduced to provide objective measurements of the blood flow, as well as to gauge the capability of concentration and excretion of the transplanted kidneys. However, the findings whether qualitative or quantitative all have overlapping zones. There is no abnormal image, graphic, or numeric index absolutely specific for any of the possible posttransplant renal parenchymal complications. The differentiation of such conditions may best be achieved through chronologic association of the sequential changes, with or without quantification, detected in serial studies with the clinical presentation and findings.