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 131 I-o-iodohippurate sodium or iothalamate extraction in patients with renal artery stenosis (RAS). This study investigated the effect of captopril on another renal radiopharmaceutical, 99m Tc-mercaptoacetyltriglycine (MAG3), in particular its plasma clearance. Methods: Three groups of patients were studied. Group I contained 22 patients with hypertension but a low likelihood of RAS according to negative captopril renography results, confirmed by angiography in 5. Group II contained 22 hypertensive patients with RAS documented 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 compared with baseline conditions, whereas in 18 of 22 group II patients, clearance decreased (P < 0.01). In group III patients, clearance was not significantly altered. The clearance decrease in group II did not correlate with the blood pressure decrease or plasma renin activity increase during captopril renography. Conclusion: Renal function assessed by MAG3 plasma clearance decreases in hypertensive patients with RAS but increases in patients without RAS. MAG3 clearance measurements during baseline and captopril renography can thus serve as additional diagnostic information when investigating patients with hypertension for the possibility of an RAS.