Transplanted Kidney Function Evaluation

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The best option for the treatment of end-stage renal disease is kidney transplantation. Prompt diagnosis and management of early posttransplantation complications is of utmost importance for graft survival. Biochemical markers, allograft biopsies, and imaging modalities are used for the timely recognition and management of graft dysfunction. Among several other factors, improvements in imaging modalities have been regarded as one of the factors contributing to increased short-term graft survival. Each imaging procedure has its own unique contribution to the evaluation of renal transplant dysfunction. In the era of multimodality imaging and emerging clinical considerations for the improvement of graft survival, evaluating an imaging modality in its own right may not be relevant and may fall short of expectation. Recognized as being mainly a functional imaging procedure, radionuclide imaging provides valuable information on renal function that cannot be obtained with other imaging modalities. For evaluating and establishing the current place, indications, and potential applications of radionuclide renal transplant imaging, a classification of renal allograft complications based on renal allograft dysfunction is essential. The major factor affecting long-term graft loss is chronic allograft nephropathy. Its association with early posttransplantation delayed graft function and repeated acute rejection episodes is well documented. Long-term graft survival rate have not improve significantly over the years. Imaging procedures are most commonly performed during the early period after transplantation. There seems to be a need for performing more frequent late posttransplantation imaging for the evaluation of acute allograft dysfunction, subclinical pathology, and chronic allograft changes; for understanding their contribution to patient management; and for identification of pathophysiological mechanisms leading to proteinuria and hypertension. With its unique advantage of relating perfusion to function, the potential for radionuclide imaging to replace late protocol biopsies needs to be investigated.

Section snippets

Renal Transplant Complications

There are various schemes used for the classification of renal transplant complications. The most commonly used ones either classify them as surgical vs medical or, depending on the localization of the underlying etiology, as prerenal, renal, and postrenal. Surgical complications comprise fluid collections, urinary obstruction, and vascular complications. Medical complications are related to parenchymal pathologies as acute tubular necrosis (ATN), acute rejection (AR), and drug toxicity.

From

Renal Function Tests

Renal transplant function is commonly monitored using serum creatinine level. Its production is dependent on age, gender, and muscle mass. Serum creatinine concentrations may remain within the reference range until approximately half of renal function has been lost. Plasma cystatin C level, 24-hour urinary output, and 24-hour creatinine clearance are among the measures used for the evaluation of renal function in transplant recipients. Creatinine reduction ratio and 24-hour urine creatinine

Radionuclide Imaging

Renal scintigraphy is a valuable approach to assess the 3 sequential phases of renal function. The first phase consists of the rapid dynamic imaging that is done during the first minute after tracer injection. This evaluates perfusion. The second phase is the period in which the nephrons extract the tracer from the blood and excrete it by glomerular filtration or tubular secretion or both. The third phase is the period during which the tracer drains through the pelvicalyceal system. The

Diagnosis of Early Posttransplantation Complications

A single study alone may prove to be diagnostic in cases of urinary leaks and renal artery thrombosis and may suggest the presence of several early parenchymal complications. Radionuclide imaging may be more helpful in isolated cases of ATN or AR. Initially accepted assumption of serial radionuclide imaging during the early posttransplantation period to be useful for a specific diagnosis is questionable. This necessitates the transport of patient to Nuclear Medicine Department several times

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