[Computed tomography as an aid in the differential diagnosis of radiolucent stones and tumors of the upper urinary tract].

The difficult differential diagnosis of urothelial tumors and nonopaque calculi of the upper urinary tract has been considerably improved by the introduction of computed tomography (CT) in urological diagnosis. Nonopaque calculi although urographically not visible can be determined by CT. Usually urothelial tumors can be traced by CT without invasive methods. In case of doubt in addition to the primary scan a so called flow-study, after application of contrast medium, will furnish additional information. The diagnostic facilities provided by CT are illustrated in 18 cases.