Evidence for a renovascular component in hypertensive patients with late radiation nephropathy

Abstract

Purpose : This study was undertaken to investigate whether the hypertension observed in a subgroup of patients with progressive radiation-induced nephropathy has a renovascular component. Methods and Materials : Fifteen patients with prospectively documented renal injury after high-dose radiation treatment for various abdominal malignancies were studied, 8 of them having hypertension. 99mTc-DTPA renography and plasma renin activity measurements were performed before and after an oral dose of 50 mg captopril. In patients with a positive captopril renography, a selective angiography was performed to exclude preexisting central renal artery stenosis and to assess the type and extent of the vascular changes. Results : The captopril 99mTc-DTPA renography demonstrated a longer time until maximal renal activity ( T max) compared with the baseline study in five out of eight hypertensive patients. This increase in T max was observed in both high-dose (40 Gy/5.5 weeks) and in low-dose (12–13 Gy/3 weeks) irradiated kidneys. No increase in T max was observed in the normotensive patients. In the five hypertensive cases with an increased T max, selective angiography demonstrated severe stenotic and tortuous changes in the small intrarenal branches of the high-dose irradiated kidneys without stenosis of the main renal artery. Captopril induced an increase in peripheral plasma renin activity in the hypertensive group, but not in the normotensive patients. Conclusion : These data suggest a radiation-induced hypertension, mediated by the renin-angiotensin system due to damage in predominantly small renal arteries. It was possible to demonstrate hypertensive changes with a captopril 99mTc-DTPA renography, even after presumed subthreshold radiation doses for clinical radiation nephropathy