How to Obtain Perfect Positioning for Renal Flow Scintigraphy Using 99mTc-MAG3

Assessment of the kidney's vascular flow is a vital component of the renal scan; however, achieving perfect positioning for a Tc-99m-mercaptoacetyltriglycine (Tc-99m-MAG3) renal scan can be an uphill struggle, even with a recent CT scan to refer to. Typically, the kidneys are located bilaterally and posteriorly near the upper lumbar vertebrae, with the left kidney slightly more superior than the right (Fig. 1). The quick pace of renal arterial flow leaves little room to readjust positioning should the kidneys not be in the field of view (1). Typically, the aorta is visible within 1 s after injection, and the kidneys can be viewed within 5-6 s. Maximal kidney activity is usually seen within 30-60 s after injection. Thus, it is essential to have correct positioning from the start of the scan. Too often, technologists say, "As long as the kidneys are in the field of view, we are good." However, interpreting physicians favor having the kidneys and bladder in all images to assess image data accurately.