The diagnosis of medullary sponge kidney traditionally was established by means of intravenous pyelography. Beginning in the mid-1990s, intravenous pyelography rapidly was supplanted by computed axial tomography as the preferred imaging study for evaluating patients with renal stone disease. Conventional computed tomographic imaging has not been satisfactory for diagnosing medullary sponge kidney. The introduction of multidetector-row computed tomography in 1999 allowed radiologists to acquire images composed of elements allowing the creation of high-resolution 3-dimensional displays. Computed tomographic urography is an imaging technique that provides both cross-sectional displays and images of the contrast-filled renal collecting systems, ureters, and urinary bladder that are the equivalent of intravenous pyelography. We report a case of medullary sponge kidney diagnosed by means of 3-dimensional multidetector-row computed tomographic urography.