glomerular filtration rate index regional glomerular filtration rate index The concentration of a contrast agent in the cortex (predominantly blood signal) from limited areas of one kidney is compared to the concentration in limited areas of the medulla (predominantly urine) of the same kidney to obtain the first order rate constant, k(cl). The clearance of the contrast agent can serve as a marker for the glomerular filtration rate. clinical_measurement_ontology 2021-01-07T18:50:18Z slaulede regional K(cl) PMID:14561850 CMO:0003632 regional GFR