Application of the kidney to aortic blood flow index to renal transplants.

One hundred forty-nine standardized K/A rations (renal bolus ascending slope: aortic bolus ascending slope) were performed on 33 post-transplant patients with acute or chronic rejection, obstruction, acute tubular necrosis, infection or acute hypertension after rapid intravenous injection of Tc-99m DTPA. The correlation of creatinine clearance versus the K/A ratio for 123 pairs of data performed on the same day was poor (r = 0.37), but the correlation was greatly improved (r = 0.72) when K/A ratio maxima or minima were compared with corresponding creatinine clearances performed during a nonrejection period, or acute rejection episode, respectively. Seventeen acute rejection episodes resulted in a 20% or greater decrease in the K/A ratio 16 times, but were observed as a change in the serial perfusion phase scintiphotos only five times, or in the function phase scintiphotos only six times. Of 27 significant decreases in K/A ratios, 22 were due to acute rejection, two to obstruction, one to infection, one to acute hypertension, and one was unexplained. Thus the K/A ratio is a sensitive but not specific index for following pathological changes in the renal allograft.