Renal cortical regions of interest were used prospectively to predict recoverability of renal function in 27 patients with unilateral or bilateral urinary tract obstruction. In these 27 patients 36 kidneys with short-term or long-term obstruction were studied. The 131iodine radiohippuran renogram curves were generated from areas of interest from the renal cortex and from the whole kidney. Curves generated during obstruction were evaluated quantitatively to determine if regional cortical renograms exhibited a more normal appearance than total kidney curves. After relief of obstruction renograms generated from the whole kidney were evaluated for evidence of renal functional recovery. Cortical curves obtained before relief of obstruction were judged normal, with an abnormal whole kidney renogram in 20 of 36 kidneys. The whole kidney renogram improved after relief obstruction in all 20 cases. Cortical curves for the remaining 16 kidneys before relief of obstruction had the same abnormal appearance as the whole kidney renogram. After relief of obstruction no evidence of kidney function improvement as measured by the renogram was evident in 14 kidneys. The over-all accuracy of this test of renal functional recoverability was 94 per cent. These data support the hypothesis that when cortical curves appear more normal than total kidney curves there is a strong likelihood of postoperative improvement in renal function when the obstruction is relieved. Abnormal cortical curves are associated with a poor prognosis for renal functional improvement.
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