Radionuclide Scanning in Renal Space‐Occupying Lesions

Abstract

Detection of space-occupying renal lesions by radionuclide scanning effectively commenced in 1960, when McAfee and Wagner used Neohydrin labelled with mercunr-203 as the material concentrated by the kidney. Enthusiasm for the technique was tempered with caution on account of the relatively large radiation dose delivered to the renal tubules. Many scans were, however, performed using this nuclide, but the search for a more suitable isotope was continued. Replacement of the mercury-203 by mercury-197 gave considerable improvement in radiation doses, and mercurial diuretics labelled with mercury-197 have been the mainstay of renal scanning ixi most units since. More recently chelates of technetium-99m and indium-l13m, with or without iron carrier, have been used.The advent of the gamma-camera with its high sensitivity has allowed the dse of Hippuran labelled with iodine-131 in organ imaging as well as tubular function assessment, as quite adequate pictures can be obtained during the short period of its renal transit. This has proved particularly useful in cases with renal failure.The chelates and Hippuran are considerably different pharmacologically to the mercurial diuretics, as the former are excreted by the glomeruli and concentrated in the tubules, while the latter are taken up by the tubular cells. From the scanning point of view, however, the effect is essentially the same, namely that the scan is effectively a map of the distribution of the active tubular elements of the kidney. With the chelates and Hippuran, however, it is also possible to follow the activity into the renal pelvis and the bladder. It is evident, therefore, that the majority of pathological lesions within a kidney will be " cold ", that is, with little or no uptake of the radionuclide, so it is impossible to make a pathological diagnosis on the basis of a scan alone. This is well shown in the cases illustrated in Figures 1-3, in which carcinoma, cyst and tuberculosis present very similar appearances. Rosenthall et nl. have attempted to distinguish between vascular and non-vascular lesions by assessment of blood p l activity in the lesion using an iiitravenous dose of technetium-99m. This has gisen a very fair degree of differentiation hetween renal cwts an& tumour, but optimally requires the use of a gamma-camera. We have attempted to do the same by using acid indium as the blood-pool agent and scanning the kidney with a rectilinear scanner but overlying structures, particularly the liver on the right side, have given rise to considerable difficulties.One c,ase has been reported by Caplan et a!. ('1968) of a " hot " renal tumour in which a renal tubular adenoma concentrated a labelled mercurial diuretic in excess of the normal tubular concentration.The intrinsic resolution of scanning systems is relatively poor, so that it is unlikely that any cold lesion smaller than 2 cm. in diameter would be detected within the kidney. Should the lesion be on the edge of the kidney, the notch produced is slightly more easily seen. It should be noted that...