Captopril renography. Early observations and diagnostic criteria.

This article describes the methods and the interpretation of captopril renography. The essentials of the methods are the discontinuation of diuretics, the refraining from solid foods before administration of 25 mg captopril, hydration to induce diuresis, the performing of 1-min sequential images, data acquisition with frame time not exceeding 30 sec, and the calculation of the left to right ratio. In most instances data from captopril renography can be interpreted without the presence of a baseline study. Abnormalities of the sequential images and the renal curves classified as grade 2 and 3 indicate the presence of renal artery stenosis. Besides, in unilateral stenosis, captopril induced renographic abnormality can also be observed in bilateral and segmental stenosis. Interpretation based on numeric parameters probably does not increase the sensitivity. Alterations on mercaptoacetyltriglycine (MAG3) studies are identical to the alterations observed on orthoiodohippurate (OIH) studies. In severe stenosis, alterations in diethylene-triaminepentaacetic acid studies are different from those observed in OIH or MAG3 studies. Since MAG3 provides the best images, at present MAG3 is the radiopharmaceutical of choice.