Nonurographic evaluation of renal calculous disease1
Gregory P. Borkowski, M.D.
Craig R. George, M.D.
Peter B. O’Donovan, M.D.
While excretory urography has been useful in the evaluation of patients with renal calculi, it does have certain limitations. These include (a) poor differentiation of calculi from other causes of radiolucent filling defects within the renal collecting system, (b) poor visualization because of decreased renal function, and (c) possible contraindication in patients with a history of significant allergic reaction. Computed tomography (CT) and ultrasound are noninvasive techniques which have proved to be useful in the evaluation of nonopaque calculi. The greater density discrimination of CT allows stones to be visualized as areas of increased density without the need for intravenous contrast material. On ultrasound, calculi appear as echogenic areas with posterior acoustical shadowing. These imaging modalities have also been useful for preoperative assessment of the position of renal calculi, intraoperative localization of calculi, and determination of the response of a calculus to dissolution therapy.