Differential renal function studies in the diagnosis of renal hypertension.

Over a 10-year period, positive criteria of the Howard test and the Rapoport Index have shown consistently good correlation with sustained relief or marked improvement in hypertension, in patients with main renal artery lesions. Similar correlation was obtained with ischemic criteria from histopathologic studies.Differential function studies did not reveal positive ischemic criteria in any patient operated upon for unilateral parenchymal disease. Histopathologic criteria of ischemia were also infrequent in this group. Nevertheless, marked improvement or cure of hypertension occurred in 62% of the latter. No factor can be used to predict improvement in this type of renal hypertension. Differential renal function criteria may occasionally appear to indicate renal artery ischemia in the more normal kidney in patients with unilateral parenchymal renal disease; wrong interpretation is avoided by taking differential creatinine clearance into account. Until vasopressor substances can be easily measured and accurately interpreted, aortography is indicated in selected patients.