Renovascular Hypertension

A large number of laboratory tests are currently used in an attempt to predict which hypertensive patients will benefit from surgical correction of renovascular disease. These include the intravenous urogram, the renal arteriogram, the radioactive renogram, the split renal function study, and the urea washout, none of which is now considered specific by most investigators, though each has had its enthusiastic proponents. In a further attempt to determine the predictive accuracy of each of these tests we reviewed the records of all University of Minnesota Hospital patients who underwent corrective surgery for presumed renal hypertension, and we then correlated the blood pressure response with the results of the preoperative examinations. This analysis reveals that none of the surveyed tests accurately predicted the surgical result in more than 72 per cent of the cases. Methods and Materials The charts of all patients who underwent surgery for correction of renal hypertension between 1959 and 1966 were reviewed. Of 31 such patients, 3 died in the immediate postoperative period, 1 has been lost to follow-up, and 1 was operated upon too recently for evaluation of the surgical result. The remaining 26 patients who form the basis of this report have been followed after an interval of at least one year. The preoperative evaluation of these 26 patients included aortography and intravenous urography in all cases. A radioisotope renogram was performed in 19 cases, split renal function study in 20 cases, and urea washout in 23. Intravenous urography was carried out on dehydrated patients following the rapid injection of 50 cc of 75 per cent diatrizoate contrast medium. Exposures were made at one-half, one, three, five, eight, and fifteen minutes. The urea washout test was performed in conjunction with the intravenous urography following complete opacification of both collecting systems. This usually occurred five to eight minutes after the injection of contrast medium. A rapid infusion of 40 g of urea dissolved in 500 ml of saline was started, and films were exposed every three minutes until dilution took place (21). Renal arteriography was carried out exclusively by percutaneous transfemoral catheterization, using a bolus injection of 30 to 40 ml of diatrizoate contrast medium. Radioactive renograms were obtained by means of a dual ratemeter system with 2-inch diameter sodium iodide crystals placed 8 inches from the skin surface. Patients were given nothing by mouth for six to eight hours and then studied in the sitting position. The kidneys were localized with a preliminary injection of approximately 5 microcuries of 197Hg Neohydrin. Radioactive Hippuran (20 microcuries) was then administered intravenously, and its rate of uptake and clearance recorded for thirty minutes. Most of the split function studies were done by the method of Howard (3), but in a few of the recent ones Stanley's modification (20) was employed.