GLOMERULAR FILTRATION RATE DETERMINED IN CONJUNCTION WITH ROUTINE RENAL SCAN

A method has been developed to estimate glomerular filtration rate (GFR) by means of computer evaluation of information obtained during routine renal scanning with intravenous Tc-99m DTPA.Thirty minutes of data were accumulated as a 30 sec/frame dynamic study following injection, with kidneys and a portion of the heart included in the imaging field. From the computer acquired study, a plasma activity disappearance curve was generated using(1) a region of interest outlining the imaged portion of the heart, and (2) a single blood sample obtained near the end of the study. Average plasma activity concentration during the study (PAVG) was then determined.Total urinary activity (TUA) generated from onset to conclusion of the study at time T, was determined using subsequent pre- and post-void bladder images, and measured volume and activity of the voided urine. Clearance was calculated using the formula:C1 (ml/min) = TUA DTPA (PAVG)(T)The urinary radionuclide clearance correlated highly with standard 24-hour creatinine clearance over a wide range of clearance values in thirteen patients.The method described to estimate GFR can be performed using less than 40 minutes of imaging time, requires only a single blood sample, does not require measurement of administered dose, is accurate even when the dose is partially or largely infiltrated, and unlike many popular indirect methods for estimating GFR adequately accounts for variations in volume of distribution.