What are the pros and cons of the three different imaging techniques available for urography?
CT and MRI are comparable for evaluation of the renal parenchyma, and for assessment of renal masses. However, the ability of CTU to detect small urothelial lesions is much greater than that of MRU, making it the preferred technique for evaluating the collecting systems and ureters for urothelial neoplasms.
IVU is much less sensitive than either CTU or MRU for detection of renal masses and evaluation of the parenchyma, making it less optimal than CTU or MRU in a patient undergoing evaluation for hematuria. In a patient undergoing evaluation for urothelial tumors, IVU has good sensitivity for depicting urothelial lesions. However, as detailed below, IVU requires a rigorous preprocedure preparation, making it uncomfortable for patients. For these reasons, IVU has ceded ground to CTU for most clinical indications in the evaluation of the urinary tract. It continues to be a valuable technique in evaluating patients postoperatively after urologic procedures, in order to exclude obstruction as a complication of the procedure.
Due to the multiple phases of examination and the thin sections necessary for CTU, radiation exposure is a prime concern; it can range from 15 mSv to much higher. Evolving CT techniques are focused on reducing the radiation exposure for these examinations