Posterior/anterior distribution of radiolabel on lateral renal images: Possible use in studying the retroperitoneum

At 30 minutes after intravenous administration of the glomerular renal agent TC-99m-DTPA, both right and left lateral views were obtained. We analyzed the ratio of optical densities (behind the ureter/In front of the ureter). In patients without gross renal failure or retroperitoneal disease, the ratio was always less than 1 (range 0.38 to 0.95, mean 0.68). This represents greater perfusion of the Intestine and anterior organs as compared with the retroperltoneum. Since the posterior/anterior ratio can be readily determined by computer processing or by measurement of optical density of the film, It was suggested that this might be an approach for detecting increased retroperitoneal permeability in diseases of that area or possibly In cases of renal disorders.