Report of the radionuclides in nephrourology committee for evaluation of transplanted kidney (review of techniques)

Comprehensive evaluation of renal transplants has been important in differe ntial diagnosis of medical and surgical complications in the early post-tra nsplantation period and in the long-term follow-up. If performed well, it y ields excellent functional and good anatomic information about the graft th at can be effectively used in the patient. That includes selection of patie nts for biopsy and for various drug regimens. This is true especially in pa tients with anuric acute tubular necrosis (ATN) and in patients with develo ping chronic rejection. Improving indices of renal function (effective rena l plasma flow, uptake of tubular tracers) can indicate resolution of tubula r injury (ATN) while there is still no improvement in plasma creatinine. in patients with chronic rejection, plasma creatinine increases only after ap proximately 30% of renal function is lost due to graft fibrosis. Early reco gnition of this condition could permit treatment and delay of retransplanta tion. The protocol recommended at the Copenhagen meeting includes a flow st udy, scintigram of the kidneys, prevoid and postvoid bladder image, injecti on site image (quality control), time/activity curves of the graft and blad der, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the gra ft could be performed either with Tc-99m mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Quantitative analysis of perfusion facilitates interpretation of the study during the early post-transplantati on period. ATN, common in cadaver transplants, typically shows adequate per fusion. The function phase should include images and time/activity curves. Images alone are insufficient. Quantitative data such as clearance or other indices of function and indices of tracer transit are essential for correc t interpretation of the results. Normal images and normal graft function re liably exclude clinically important complications. A single scintigram demo nstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor pe rfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chron ic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensi n converting enzyme challenge) should be used whenever indicated. Copyright (C) 1999 by W.B. Saunders Company.