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CT scan and CT Urogram
Computed tomography is a noninvasive imaging technique that uses X-ray technology to depict internal structures of the body such as the urinary tract. All kidney stones are visible on CT scans. CT scans collect X-ray images from different angles around the body to generate detailed cross-sectional images as well as three-dimensional images of the body's internal structures and organs. A computer analyzes the radiation transmitted through the body to reconstruct the images of the internal structures and organs. The new generation of CT scans allows for faster, higher-quality imaging with less radiation exposure than a standard CT scan.
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Prior to the procedure you may be asked to abstain from eating or drinking. The procedure is painless and requires the patient to lie as still as possible on a table that is guided into a machine that resembles an enormous doughnut. The machine, called a gantry, directs small doses of electromagnetic radiation toward the body from various angles. Although an abdominal scan can usually be completed in a single breath, about 10 seconds or less, the entire procedure may last 5 to 30 minutes.
A contrast medium (akin to a dye) is not necessary to diagnosis kidney stones with CT and typically is not used in emergency settings. However, if the examination is scheduled in a medical center, the urologist may follow a plain CT with a CT urogram, which uses a contrast medium to better visualize the structures of the urinary tract. If a contrast medium is to be used, patients typically will need to fast for a few hours before the procedure. The contrast medium will be injected into a vein during a CT scan. The contrast medium may, on occasion, cause an allergic reaction, most commonly hives or itchiness. In people with asthma, the allergic reaction may manifest as an asthma attack. In very rare instances, a patient may experience swelling in the throat or other areas of the body. If you experience hives, itchiness, or swelling in your throat during or after your CT scan, immediately tell the technologist or doctor.
Abdominal CT scans involve exposure to a dose of radiation that is roughly equal to the background levels of radiation an average person experiences in three years. For most patients, the benefits far outweigh the risks associated with exposure to this level of radiation. However, pregnant women are usually advised to choose alternative testing procedures or postpone getting a CT scan until after they've delivered. People with pacemakers or internal cardioverter defibrillators who have been advised to avoid MRIs can safely have a CT scan.
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