Noninvasive estimation of kidney function by x-ray fluorescence analysis. Elimination rate and clearance of contrast media injected for urography in man.

A noninvasive method for the estimation of kidney function is described. The use of radioactive tracers and the sampling of plasma and urine are omitted. The method has been used in patients referred for urography and who had therefore been injected with routine amounts of iodine-containing urographic contrast medium. After urography, the elimination rates of urographic contrast medium from both serum and finger tissue were determined and compared during a 2-hour period that began two hours after injection of contrast medium. The elimination of iodine in finger tissue was measured noninvasively using x-ray fluorescence analysis. A strong degree of correlation was found between the elimination rates from serum and finger tissue and between the total clearances calculated from the serum and finger measurements. Thus, after urography estimation of kidney function may be obtained as a fringe benefit by x-ray fluorescence measurements of the elimination rate of an iodine-containing contrast medium from tissue or from serum.