Noninvasive measurement of concurrent single-kidney perfusion, glomerular filtration, and tubular function

To assess the reliability of electron beam computed tomography (EBCT), meas urements of single-kidney renal blood flow (RBF), glomerular filtration rat e (GFR), and intratubular contrast medium concentration (ITC) of radiograph ic contrast media were quantified in anesthetized pigs before and after ace tylcholine-induced vasodilation and diuresis. EBCT measurements were compar ed with those obtained with intravascular Doppler and inulin clearance. The capability of EBCT to detect chronic changes in single-kidney function was evaluated in pigs with unilateral renal artery stenosis, and their long-te rm reproducibility in normal pigs was studied repeatedly at 1-mo intervals. EBCT-RBF (ml/min) correlated with Doppler-RBF as RBFEBCT = 45 + 1.07 (*) R BFDoppler, r = 0.81. EBCT-GFR (ml/min) correlated with inulin clearance as GFR(EBCT) = 11.7 + 1.02 (*) GFR(inulin), r = 0.80. During vasodilation, RBF and GFR increased, whereas ITC decreased along the nephron. In renal arter y stenosis, single-kidney GFR decreased linearly with the degree of stenosi s, and ITC increased along the nephron, indicating increased fluid reabsorp tion. EBCT-RBF, GFR, and ITC were similar among repeated measurements. This approach might be invaluable for simultaneous quantification of regional h emodynamics and function in the intact kidneys, in a manner potentially app licable to humans.