Determination of fractional renal function in renography with and without individually [131I]albumin-determined blood background.

Fractional renal function was determined from 122 renographies using three different blood background subtractions: with individually [131I]albumin-determined correction factors, with direct subtraction of the thorax background curve. In the latter case a systematic error was introduced, since the right kidney's fractional function was overestimated and that of the left kidney accordingly underestimated. With mean correction factors the deviation from 'true' fractional function (as determined individually with [131I]albumin) was negligible. We recommend this principle since it is simple and sufficiently accurate.