Early uroradiology techniques were based on the abdominal plain film and were, for the most part, performed for the evaluation of calculus disease (1). Subsequently, retrograde pyelography was developed, and it was first performed with the injection of contrast material directly into the ureters from a cystoscopic approach utilizing colloidal silver, air, carbon dioxide, and other compounds. Retrograde pyelography represented the first imaging study in which contrast material was used to depict anatomy and structural abnormalities.

In 1930, Moses Swick (2), a urologist, developed the first safe intravenous contrast material, Uroselectan, a single iodine atom connected to a pyridine ring. This innovation led to the development of intravenous urography (IVU). With further advancements in the composition of iodinated contrast material in the 1950s and 1960s, the modern intravenous urogram evolved (3). Initially, linear tomography of the kidneys or nephrotomography was added if a renal parenchymal lesion was suspected, and arteriography was performed when the mass was suspicious. In 1974, Bosniak (4) showed that nephrotomography increased the detection of renal masses compared to IVU alone, leading to increased use of this technique. In the late 1970s, ultrasound replaced arteriography as the adjunctive imaging modality of choice for renal masses detected with IVU. Ultrasound, even in its earliest form, was capable of differentiating solid from cystic renal lesions without ionizing radiation or contrast material. In the 1980s and 1990s, CT quickly emerged as a powerful tool in the diagnosis of many diseases of the urinary tract, including renal masses. CT also outperformed other imaging modalities in the diagnosis of renal infection, trauma, and calculi. However, IVU was still needed to image the urothelium. In the late 1990s, MRI became an important modality in the diagnosis of urologic disease, especially in patients with renal insufficiency and in patients with an allergy to iodinated contrast media. Finally, with the advent of multidetector CT, CT became capable of producing a large number of thin section images in a short period of time. As a result, the spatial, temporal, and contrast resolution became sufficient to image the urothelium. Thus, CT could be used to evaluate all major anatomic segments of the urinary tract. Protocols were developed that provided IVU-like images of the urinary tract, referred to as CT urography, and included CT scans of the abdomen and pelvis both before and after the administration of IV contrast material.

CT urography is useful in patients with hematuria. Since hematuria has many causes, a thorough evaluation of both the upper and lower tracts is needed to diagnose malignancy, infection, and other causes of hematuria. CT urography may be used to detect renal masses, urothelial tumors, and the sequelae of complicated infection. CT urography is also useful in the setting of trauma and in the identification and classification of congenital anomalies. An additional important use of CT is in the evaluation of patients with flank pain, in whom unenhanced CT scans are sufficient in most cases. Use of CT or CT urography in evaluating patients with all of the previously mentioned conditions is addressed in the following sections.

Hematuria, whether gross or microscopic, may be a sign of urinary tract pathology. Gross hematuria is alarming to both the patient and the primary care provider and often leads to referral to a urologist. Whether and how to evaluate patients with microscopic hematuria is controversial in part because there is no consensus regarding the definition of microscopic hematuria. Also, a small percentage of the normal population has microscopic hematuria. Thus, the American Urologic Association commissioned a panel to formulate best practice guidelines on asymptomatic microscopic hematuria. This document is used here to review our recommendations (29).