Computed tomography (CT—see also Computed Tomography (CT)) and magnetic resonance imaging (MRI—see also Magnetic Resonance Imaging (MRI)) scans are good tools for assessing the size and location of abdominal organs. Additionally, cancerous (malignant) or noncancerous (benign) tumors are often detected by these tests. Changes in blood vessels can be detected as well. Inflammation, such as that of the appendix (appendicitis) or diverticula (diverticulitis), usually can also be detected. Sometimes, these tests are used to help guide x-ray or surgical procedures.
For CT and MRI of the digestive tract, doctors may give people substances that can be seen on the imaging test (contrast agents) to help distinguish one tissue or structure from its surroundings. Contrast agents may be given by mouth, by vein, by enema, or in combination.
Regular CT does not show the lining of the intestines well. A variation of the test, called CT enterography, allows doctors to clearly see the lining of the small intestine and look for tumors or narrowing of the intestines resulting from inflammation (strictures). For this test, people drink a large volume (about 1.6 quarts [1.5 liters]) of a liquid contrast agent such as barium. The contrast agent distends the small intestine so that doctors can see it better.
Magnetic resonance (MR) enterography is similar to CT enterography in that people drink a contrast agent before pictures are taken of their small intestine. It helps doctors see inflammation, bleeding, and other problems. This test is typically reserved for younger people, especially those with inflammatory bowel disease, so they are not exposed to radiation.
This test generates two-dimensional and three-dimensional images of the colon that may show tumors or other problems.
For this test, people drink a contrast agent, and their colon is inflated with gas from a tube inserted in the rectum. Before the test, people are given laxatives or enemas similar to those required for a regular colonoscopy to thoroughly remove stool. Although CT colonography is able to detect abnormal growths (intestinal polyps) or even colon cancer, people still need to have a colonoscopy to remove any polyps or abnormalities detected during the test.