Noninvasive determination of glomerular filtration rate using x-ray fluorescence.

Accurate glomerular filtration rates (GFR) can be calculated based on the infusion of small amounts of nonradioactive iothalamate and collection of plasma samples for assay by x-ray fluorescence. This innovation permits frequent clearance determinations in patients without the hazard of repeated radiation exposure and without the necessity of catheterization of the bladder for urine samples. Thus, the technique becomes feasible in children, transplant patients, and other needing accurate and frequent GFR determinations.