Radioisotopic Renography

Abstract

Sodium ortho-iodohippurate (Hippuran) I 131 renography has been performed by a standardized technic in patients with renal artery stenosis, pyelonephritis, primary aldosteronism, pheochromocytoma, and renal tubular acidosis with nephrocalcinosis, as well as in patients in whom the hypertension was apparently not secondary. Fifty of 94 patients studied were found to have abnormal renograms. In patients with renal artery stenosis, all of 37 patients studied had values on the renogram that were outside the range for normal subjects. Although the renographic findings were not considered diagnostic of renal artery stenosis, certain abnormalities of the renogram were commonly observed in the presence of such lesions. When a unilateral delay in the appearance of maximal radioactivity was associated with delayed disappearance ot the medium, renal artery stenosis was frequently observed. Less pronounced differences in the function of the two kidneys were observed in patients with bilateral renal artery stenosis. A state of antidiuresis was often found helpful in the detection of less severe differences in renal function. In patients with predominantly unilateral pyelonephritis, the renographic abnormalities were qualitatively consistent with the degree of impairment of renal function. Bilateral abnormalities were observed in two patients who had bilateral parenchymal disease. The abnormalities on the renogram did not permit distinction between renovascular and renal parenchynal disease. Pyelonephritis associated with obstructive uropathy revealed findings highly suggestive of renal artery stenosis. Distinction from renovascular lesions could be determined with the aid of urographic studies. Only three of 44 patients with essential hypertension had abnormal renograms. The renograms, normal and abnormal, revealed essentially equal function of the two kidneys. The patients with abnormal renograms were not found by other technics to have evidence of secondary hypertension. The patients who were found to have pheochromocytoma and primary aldosteronism had normal isotope renograms. The patient with renal tubular acidosis and nephrocalcinosis had a bilaterally abnormal renogram and severe impairment of total renal function. The presence of a normal isotope renogram, as performed in our laboratory, is considered strong evidence against the existence of a renal or renovascular cause for secondary hypertension.