A SIMPLE, RELIABLE METHOD OF MEASURING GLOMERULAR FILTRATION RATE USING SINGLE, LOW DOSE SODIUM IOTHALAMATE I131

• Published in: Pediatrics (Evanston) 1969-03, Vol.43 (3), p.407-415
• Main Authors: Cohen, Melvin L., Smith, Fred G., Mindell, Robert S., Vernier, Robert L.
• Format: Article
• Language: English
• ISSN: 0031-4005; 1098-4275
• DOI: 10.1542/peds.43.3.407

The renal clearances of sodium iothalamate I131 after a single intravenous dose of 10 µCi were compared with inulin clearances and endogenous creatinine clearances. In a total of 40 comparative studies made between the isotope and inulin clearances, correlation was excellent (r = .995) with a very small standard error (±5.9), suggesting that sodium iothalamate I131 clearance accurately measures glomerular filtration rate. In 43 comparative studies between endogenous creatinine and inulin clearances, correlation was good (r = .935) only when determined simultaneously, and even then the standard error was so great (± 18.7) that any individual creatinine clearance was of limited value. In performing the isotope clearance, adequate hydration is maintained orally. Ten microcuries of sodium iothalamate I131 are injected intravenously. After a 30 to 60 minute equilibration period, the bladder is emptied by voiding and a blood specimen obtained. A timed, voided urine is then collected and again a blood specimen obtained at the time of voiding. Both blood specimens and the urine are counted in a well-type scintillation counter with gamma spectrometer. The mean of the beginning and end-point plasma radioactivity is used in the clearance formula. This isotope method is recommended as the test of choice in measuring glomerular filtration rate.