Tomographic levels for intravenous urography: CT-determined guidelines.

The selection of levels for tomographic sections of the kidneys during intravenous urography has previously been based on empirical observation. Three hundred abdominal computed tomographic scans were analyzed for the anteroposterior (AP) midpoints of the kidneys and their relationship to the patient's AP abdominal diameter. A graph for selection of tomographic levels was generated and compared with existing methods. These guidelines enable a more objective approach to urographic tomography.