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

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 (Tmax) compared with the baseline study in five out of eight hypertensive patients. This increase in Tmax 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 Tmax was observed in the normotensive patients. In the five hypertensive cases with an increased Tmax, 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.