الفهرس 
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Abstract
Comprehensive evaluation of transplanted kidney is important in differential diagnosis of medical and surgical complications in the early post-transplantation period and in the long-term follow-up (Dubovsky et al,1999). In evaluating the recipient with graft dysfunction, clinicians can choose among several imaging modalities. renal biopsy is often required as a gold standard for diagnostic purposes. However, because of the inherent risks of a kidney biopsy, noninvasive imaging in diagnosing causes of graft dysfunction is a highly desired tool used and needed by the transplant community(Asif,2014).precise diagnosis of renal transplant complications is very important as many complications are potentially treatable if detected early. Ultrasound is typically the initial imaging modality used to evaluate vascular patency, the collecting system, and for perinephric fluid collections. CT, MR imaging, and nuclear medicine studies play a complimentary role (courtney et al,2016) ). Nuclear medicine renal scans (using radioactive 99mTc DTPA or 51Cr-EDTA) are considered the gold standard for the evaluation of kidney function because of their accuracy (Stevens et al,2009). also enable the assessment of split renal function, which can help to identify the better functioning kidney that should remain with the donor (Wahba et al,2016). The ability to assess split renal function is particularly important for donors with GFRs that only just meet acceptability criteria (Stevens et al,2009). And also is essential for side selection and a sufficient long-term residual renal function for both the donor and the recipient after transplantation (Sarah et al, 2016).
Renal scan is preferred Owing to the noninvasive nature, ready availability, and efficacy, If performed well, it yields excellent functional and good anatomic information about the graft that can be effectively used. That includes selection of patients for biopsy and for various drug regimens. radionuclide studies remain widely utilized following renal transplantation for monitoring changes in the functional status and detection of detrimental complications of the transplanted kidney. Whereas surgical complications, including vascular occlusion, urine extravasation, drainage obstruction, hematoma, or lymphocele formation, can often be detected effectively(Eddy,1992). This is true especially in patients with anuric acute tubular necrosis (ATN) and in patients with developing chronic rejection. the role of radionuclide renography is no longer to diagnose AR or ATN. Rather, the real value of these parameters lies in the follow-up of ATN and AR. The monitoring of severely prolonged ATN cases is of great concern to the nephrologist and may assist in determining the timing of biopsy and in detecting improvement in ATN.
Improving indices of renal function (effective renal plasma flow, uptake of tubular tracers) can indicate resolution of tubular injury (ATN) while still no improvement in plasma creatinine. In patients with chronic rejection, plasma creatinine increases only after approximately 30% of renal function is lost due to graft fibrosis. Early recognition of this condition could permit treatment and delay of re transplantation. The protocol recommended at the Copenhagen meeting includes a flow study, scintigram of the kidneys, prevoid and postvoid bladder image, injection site image (quality control), time/activity curves of the graft and bladder, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the graft could be performed either with 99mTc mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Normal images and normal graft function reliably exclude clinically important complications. A single scintigram demonstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor perfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chronic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensin converting enzyme challenge) should be used whenever indicated(Dubovsky et al ,1999).Dimercaptosuccinic acid (DMSA) renal scan is the gold standard imaging method to assess renal parenchymal defects(i.e., hypoplasia, dysplasia, scars) (Maryse et al,2017).
Conclusion:-
-RS has its merits for the evaluation of complications after kidney transplantation, especially for vascular and/or urological complications. However, providing a clear recommendation for the use of either RS or US during the early postoperative period is not possible, Several studies have described the use of RS for the diagnosis of acute rejection, however, differentiating between rejection and acute tubular necrosis remains difficult. For the diagnosis of vascular complications, RS has been described as an alternative for invasive procedures. For urologic complications, studies support the use of RS in combination with routine ultrasonography (US) surveillance. For the diagnosis of postoperative fluid collections, lymphoceles show areas with lack of tracer uptake in contrast to the accumulated tracer uptake in urinomas. Altogether, RS should be considered in case of non-acute complications, and if US provides insufficient results. Early diagnosis of vascular and urological complications can contribute to a more specific surgical approach and better post-transplant outcomes.
Late AR episodes are reported to have more negative effect on graft survival as compared with early ones(Alarrayed et al,2011)Radionuclide imaging can be used for the diagnosis of late AR in high-risk patients . It has the unique advantage of relating perfusion to function. This information might reveal data regarding the functional evolution of CAN and may have the potential of affecting patient treatment protocols .Comparative studies with protocol biopsies at certain predetermined intervals after the transplantation may provide useful information in patient management .I n this way, the potential of radionuclide imaging to replace protocol biopsies can be identified. Comparative Studies Between İmaging Modalities Radionuclide imaging and Doppler sonography seem to have similar performance in evaluating renal transplant perfusion. However, scintigraphy has the added advantage of providing functional information .Comparative studies with contrast enhanced sonography and scintigraphy may be needed for differentiating parenchymal pathologies. A similar study can be conducted for evaluating perfusion and function impairment incases of CAN.
Patient Management In most transplant centers, the first response to deterioration of transplant function is the initiation of pulse steroid treatment. In cases of subclinical rejection or border line cases, the decision to treat or not may be based on functional impairment detected on scintigraphy .In cases of AR, initiating treatment with steroids or more aggressive options such as monoclonal antibody induction therapy may be based on scintigraphy findings(Aktas et al ,2002) Comparative studies with protocol biopsies might be needed in cases of sub clinical pathology.
Recommendations:-
-Using nuclear medicine in measurement of donar GFR as it consider the gold standard for evaluation of renal function.
- a base line study performed within 24–48 h of transplantation was found to contain important prognostic information in addition to its role in evaluating graft perfusion in the immediate post-operative setting it have a role in the prediction of long term allograft function. A recent study found that quantitative assessment of Tc-99m DTPA perfusion scintigraphy performed within 2 days after transplantation was useful in the prediction of long-term graft function up to 5 years and was superior to measurement of intra-renal resistance index by Doppler ultrasonography.
-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. serial radionuclide imaging during the early post transplantation period is useful for Comparison with baseline renal scintigraphy, performed within couple of days after transplantation, provide information to determine whether function is improving or deteriorating.
Ethical considerations:-
-This research is approved by ethical cometee of faculty of medicine sohag university.