A new, easier method for determining split renal function

Investigators reported a new method for determining split renal function that's as good as the most popular method but simpler to use, according to their study published in the March 2016 issue of the European Journal of Nuclear Medicine and Molecular Imaging.

“The most popular method is probably not the best method, because the best method is hard to use,” said corresponding author Carl Wesolowski, MD, of the Department of Medical Imaging at the University of Saskatchewan, in Saskatoon, Canada.

Split renal function (SRF) is used to determine the separate contribution of each kidney to total renal function. Currently, the most popular approach to calculate SRF is to use either the integral (IN) or the Patlak-Rutland (PR) methods. However, these methods involve extra “regions of interest” and additional mathematical analysis.

The researchers’ new method, blood pool compensation (BPC), uses the same equipment—a gamma camera—but requires only three regions of interest (one from the blood pool and two from the kidneys) and less mathematical correction.

“We take the activity over a short period of time and then we plot the activity in each of the kidneys against the activity in the liver,” explained study co-author Michal Wesolowski, PhD, also of the University of Saskatchewan. “Using this number, we can extrapolate kidney activity to a point at which there were zero counts in the liver. So the zero counts show the amount of kidney activity that is only from kidney drug extraction—that is, kidney function.”

For this study, the researchers acquired data from the Database of Dynamic Renal Scintigraphy on 107 patients (45 men and 62 women; average age 53) who had a variety of kidney and urinary tract diseases. The researchers then calculated split renal function using the BPC method, which they compared to the PR and IN methods.

The BPC technique produced similar SRF values as the PR method, but with fewer operator steps, the researchers reported. The IN method showed a significant difference in values compared with either the PR or BPC method.

“The data in this study show that the BPC method compensates for intrarenal vascular activity with only three ROIs. It is therefore a new reliable method for quality control in the calculation of SRF,” the authors concluded.

Because this study didn’t include children, the researchers are now undertaking a retrospective study in a large cohort of pediatric patients to further validate the BPC method.