RENAL TRANSIT TIME OF 99mTc-DIETHYLENETRIAMINEPENTACETIC ACID (DTPA) IN NORMAL DOGS

The transit time of 99mTc-DTPA in the kidneys is an indicator of renal function that has been used in humans for the diagnosis of renal obstruction, renal artery stenosis, and rejection of renal transplants. Its use, however, has not been reported in the dog. 99mTc-DTPA scintigraphy was performed in 8 normal dogs and the time of peak was calculated as the time between the injection and the maximum renal uptake. Deconvolution analysis was performed to estimate the renal retention function using 3 different techniques, i.e. the matrix method, the fast Fourier transform (FFT) method, and the constrained least square method. The parenchymal and whole kidney mean transit times were calculated from the deconvolved renogram using alternatively the thorax and the aorta as the input function. Average mean transit times ranged from 137 to 184 seconds. Parenchymal mean transit time was significantly shorter than whole kidney mean transit time (P<0.03). Mean transit time calculated with the thorax as the input function was significantly longer than mean transit time calculated with the aorta (P<0.001). No differences were observed between mean transit time calculated with the matrix, FFT and constrained least square methods.