Urography

ALSO KNOWN AS: Intravenous pyelography (IVP), oral urography, retrograde urography, magnetic resonance urography, computed tomography urography

DEFINITION: Urography allows an assessment of the health and functioning of the urinary system by injecting a contrast material (dye) into the bloodstream. When this contrast material reaches the urinary tract, its soft-tissue structures become visible on imaging scans, allowing abnormalities to be detected.

Cancers diagnosed:Kidney cancer (renal cell carcinoma), cancer of the ureters, and bladder cancer

Why performed: The urinary system is composed of the kidneys, ureters, bladder, and urethra. The kidneys are two bean-shaped organs located in the lower back below the rib cage. Their function is to filter blood, remove waste products, and help maintain the proper balance of fluid in the body. The ureters carry excess water and waste materials from the kidney to the bladder, where these waste materials are stored. The urethra removes this urine from the body. Urography allows these structures to be examined for cancer and other abnormalities in a non-invasive way.

Most often, urography is done for reasons unrelated to cancer. Kidney stones, for example, can cause obstruction in the urinary system accompanied by extreme pain. In this case, urography is done on an emergency basis to locate the obstruction. Cancer tumors can also cause obstruction or blood in the urine. Urography to detect cancer is done on a nonemergency basis in a center or other outpatient setting.

Urography can be done in several different ways using various imaging techniques. Sometimes it is necessary to use more than one method to acquire precise information about the location of tumors. Previously, excretory urography was most commonly used. However, this method has largely been replaced, though many argue it still has its advantages. In intravenous pyelography (IVP), a dye containing iodine is injected into a vein in the hand or arm. When the dye reaches the urinary tract, the tissues become visible on conventional X-rays. The only difference between oral urography and IVP is that the individual drinks the dye instead of having it injected. Retrograde pyelography is similar to an IVP; only the dye is placed directly in the urinary tract by way of a catheter (thin tube) inserted into the urethra. In computed tomography (CT) urography, contrast material is injected into the bloodstream, but instead of using conventional X-rays to visualize the kidneys, ureters, and bladder, a CT scanner takes multiple cross-sectional images of the body and uses a computer to compile a three-dimensional image. In urography, contrast material is injected, and then the individual is placed in a special tube while a three-dimensional picture is obtained through magnetic resonance imaging (MRI). This type of urography is used most often to locate bladder cancer that has spread into the pelvic region.

Patient preparation: For nonemergency urography, the physician will review the patient’s medications to make sure that they do not interact with the contrast material. Patients should tell their physicians if they are allergic to seafood or iodine, as this increases the likelihood that they may have an allergic reaction to the contrast dye. Women who are or think they might be pregnant should not have urographic tests that expose them to X-rays.

The night before the test, the patient takes a laxative to empty the bowel and should not eat or drink on the day of the test. During the test, the patient will wear a hospital gown.

Steps of the procedure: The contrast material is injected into a vein (most commonly), injected into the urethra, or given by mouth. The patient may briefly feel a warm, tingling sensation. In rare cases, the patient can develop breathing problems or experience swelling in the throat or elsewhere. This is a sign of an allergic reaction, and the physician should be notified immediately.

The patient is placed on the X-ray table, and a series of X-rays are taken at timed intervals, usually at zero, five, ten, twenty, and sometimes forty minutes. While each X-ray is being taken, the patient must remain still. Between X-rays, the patient may move. For the final X-ray, the patient is asked to urinate, and an X-ray is taken of the bladder. CT and MR urography are very similar. MR urography takes about one hour and requires the patient to remain still during that time.

Advances in imaging have improved the ability of urography to diagnose the urinary system and have been especially helpful in diagnosing bladder cancer. Combining urography with narrow band and blue light cystoscopy has made identifying bladder cancer easier. Advances in ultrasound technology have also added to the effectiveness of urography.

After the procedure: After the procedure, the patient may eat, drink, and resume normal activities. The patient may have a mild headache or slight nausea from the contrast material. Urine will appear normal; the contrast material does not change its color.

Risks: This is a minimally invasive procedure with few risks. Rarely does a patient have a serious allergic reaction to the contrast material. Although X-rays are very safe, pregnant women should not have them because of potential damage to the developing fetus. These women can have MR or CT urography, neither of which uses X-rays.

Results: In a healthy kidney, the dye will show up on the X-rays soon after it is injected. In people with kidney damage, the dye takes longer to appear in the X-rays.

Bibliography

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Cellina, Michaela, et al. "Computed Tomography Urography: State of the Art and Beyond." Tomography, vol. 9, no. 3, 2023, pp. 909-930, doi.org/10.3390/tomography9030075. Accessed 17 June 2024.

Cowan, Nigel C. "CT Urography for Hematuria." Nature Reviews: Urology, vol. 9.4, 2012, pp. 218–26.

Dym, R. Joshua, Victoria Chernyak, and Alla M. Rozenblit. "MR Imaging of Renal Collecting System with Gadoxetate Disodium: Feasability for MR Urography." Journal of Magnetic Resonance Imaging, vol. 38.4, 2013, pp. 816–23.

Guermazi, Ali, ed. Imaging of Kidney Cancer. New York: Springer, 2006.

Mathur, Mahan, and Justin A. Siegal. “Urography: Practice Essentials, Preparation, Technique.” Medscape Reference, 1 Dec. 2022, emedicine.medscape.com/article/1890669-overview?form=fpf. Accessed 17 June 2024.

Niederhauser, Blake D., et al. "Utility of Gadolinium-Enhanced MR Urography in Detection of Bladder Carcinoma." European Journal of Radiology, vol. 82.3, 2013, pp. 472–77.

Madaan, Prateek K., and Rohini G. Ghasi. "Conventional Uroradiology with Excretory Urography: A Forgotten Art?" The British Journal of Radiology, vol. 95, no. 1132, 2022, doi.org/10.1259/bjr.20210949. Accessed 17 June 2024.

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