Captopril-induced changes in MAG3 clearance in patients with renal arterial stenosis and the effect of renal angioplasty

Angiotensin-converting enzyme inhibition by captopril decreases renal I-131 -o-iodohippurate sodium or iothalamate extraction in patients with renal ar tery stenosis (RAS). This study investigated the effect of captopril on ano ther renal radiopharmaceutical, Tc-99m-mercaptoacetyltriglycine (MAG3), in particular its plasma clearance. Methods: Three groups of patients were stu died. Group I contained 22 patients with hypertension but a low likelihood of RAS according to negative captopril renography results, confirmed by ang iography in 5. Group II contained 22 hypertensive patients with RAS documen ted by angiography and positive captopril and plasma renin response. Group III contained 10 patients after successful percutaneous transluminal renal angioplasty (PTRA) with negative captopril renography results. The 60-min, single-sample technique was used for measurement of the plasma clearance of MAG3 during baseline and captopril renography. Results: In 18 of 22 group I patients, clearance increased (P < 0.01) during captopril renography comp ared with baseline conditions, whereas in 18 of 22 group II patients, clear ance decreased (P < 0.01). in group ill patients, clearance was not signifi cantly altered. The clearance decrease in group II did not correlate with t he blood pressure decrease or plasma renin activity increase during captopr il renography. Conclusion: Renal function assessed by MAG3 plasma clearance decreases in hypertensive patients with RAS but increases in patients with out RAS. MAG3 clearance measurements during baseline and captopril renograp hy can thus serve as additional diagnostic information when investigating p atients with hypertension for the possibility of an RAS.