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Radiographic Tests in GI
Radiographic Tests in Gastroenterology
Gastroenterologists often order radiographic tests to help diagnose diseases of the gastrointestinal tract. Common complaints that may lead to such testing include abdominal pain, nausea, vomiting, heartburn, diarrhea, constipation, blood in the stool, bloating, weight loss, and abnormal laboratory tests. This chapter describes the more commonly performed radiographic tests.
- Plain X-rays
Abdominal X-ray
This is a traditional type of x-ray picture. This is the type of x-ray that looks black, white and gray. An x-ray sees the intestines better than other digestive organs. It can see if too much air is inside them or see if air has leaked out of them. It can also see if something metallic has been swallowed. Usually this is done when someone is vomiting or having pain in the belly to look for a blockage. It can be taken while laying down or standing up. This test does not take long to do.
Sitz Marker Study
This test uses the same plain x-rays as mentioned above. They are taken after you swallow a pill that lights up on an x-ray. This pill has little rings in it called sitz markers. After swallowing the pill, an x-ray is taken of the large intestine (colon). Then another x-ray is taken every few days. These pictures are looking to see how many rings are left. Often this test is done when someone has constipation. This test may need three or four plain x-rays to be done over a week. If rings are seen taking a long time to move, then that confirms the colon is slow. Other times they can be seen stuck in one place which may be from a blockage.
- Fluoroscopy (Barium) Studies
Barium/Gastrografin Esophagram (Barium Swallow)
Barium and gastrografin are types of contrast or dye. Dyes are liquids that light up on an x-ray. Barium is thick, white and chalky. Gastrografin is a thin, clear, sweet liquid. During this special x-ray, pictures are taken as dye is swallowed. Sometimes you are also asked to swallow a barium pill. This can help show if there is a narrowing in the esophagus. In addition to being done for trouble swallowing, this test is also done if choking or coughing occurs when eating. It can also be done to make sure there isn’t a leak after surgery on the esophagus.
Upper Gastrointestinal Series and Small Bowel Follow Through
An upper gastrointestinal (GI) series is a barium study that looks past the esophagus. This test shows dye going into the stomach and the first part of the small intestine. If the entire small intestine is seen, then it is called a ‘follow-through’ test. Like the swallow study, this test can see narrowings or irritation. Usually this is done if vomiting or abdominal pain is happening. Another time it is used a lot is in people with Crohn’s disease. Crohn’s disease can cause irritation and swelling of the small intestine. This type of x-ray can see if that is currently going on or not.
Barium/Gastrografin Enema and Defecography
These tests involve dye being squirted up the bottom and into the colon. This dye can be made of barium or gastrografin. In enema x-rays, the entire colon can be seen. Before doing this test, the colon must be cleaned out. This is done by drinking medicine to flush it, similar to before a colonoscopy. Once the dye is sprayed into the colon, x-rays can see the inside of the colon. This test can see if there are any growths, pockets, narrowings, or signs of inflammation. Sometimes this test can be used instead of a colonoscopy to look for polyps. Another time is if a colonoscopy cannot reach the end of the colon. This test can also look for leaks after colon surgery.
Defecography is similar in that a pasty dye is squirted up the bottom. But the goal is not to see the whole colon. Instead, it is used to see how difficult it is to have a bowel movement. You will be asked to sit on a toilet and try and push the dye back out. Using x-rays, it can tell how well your muscles are working. It can also see if anything is preventing a bowel movement from happening.
- Ultrasound Studies
Abdominal Ultrasound, Doppler Ultrasound, and Doppler Mesenteric Ultrasound
An ultrasound is not an actual x-ray. Instead of using x-rays to see a picture it uses sound waves. Gel is placed onto the skin and a small probe then sits on top. The different sound waves bouncing around show the internal organs. These can include the liver, gallbladder, bile ducts, pancreas, and appendix. A common reason to use this test is to look for stones in the gallbladder. Another is to look at the liver in detail. It can also show if anything is stuck in the bile ducts. An extra tool that can be used is something called doppler. This is where the ultrasound looks at the blood vessels. Typically, it looks at the veins going to and from the liver. There can be blockages or clots in those veins, and this is a good test for that. A mesenteric doppler looks at the main arteries that bring blood to the digestive organs. Again, it is done to look for narrowings or blockages there.
- Computed Tomography Studies
Computed Tomography (CT) Scan, Computed Tomography Angiography (CTA) or Venography (CTV)
A computed tomography scan, or CT scan, is an advanced type of x-ray. It is done while you are laying down on a table. The table then moves through an x-ray beam. This beam can take hundreds of high-quality pictures. The pictures are of the body as if it were sliced across the middle every few millimeters. Typically, dye is swallowed beforehand and/or dye is given in the vein to see the internal organs better. Some common reasons this test is done is to look for the cause of abdominal pain, vomiting or weight loss. A CT angiography or CT venography are special scans to look at blood vessels. These are done when low blood flow to the digestive tract is possible. A CT angiography can also be used to see where someone is bleeding into the digestive tract.
Computed Tomography Enterography (CTe)
CT enterography is another special type that looks just at the small intestine. This type requires drinking more dye than usual and is most helpful if someone has Crohn’s disease. When laying on the table for this test, dye will also be injected into the vein. Together these dyes will helps show if there is irritation, narrowing or scarring of the small intestine. It can also show complications of Crohn’s disease such as sinus tracts (fistulae) or pockets of pus (abscesses).
Computed Tomography (CT) Colonography (Virtual Colonoscopy)
A virtual colonoscopy, is a special type of computed tomography scan. However, this test is used to look just inside the colon. It is like doing a colonoscopy but without the camera going inside. Instead, just air is put inside which allows x-rays to see the inside of the colon. This will show if any growths, polyps, or cancers are in the colon. It can miss small growths though. Before doing the test, a solution needs to be swallowed at home. This solution will clean out the colon. That will let the x-rays see the inside better. However, you are awake for this test. That means you do not need anesthesia or sedation and can drive to it yourself. There can be some pain with this test from the air. If a growth or polyp is seen, then a colonoscopy will be needed. If it is normal, then another one can be done in five years.
- Magnetic Resonance Studies
Magnetic Resonance Imaging (MRI), Magnetic Resonance Angiography (MRA)
Magnetic resonance imaging, or MRI, is another special type of x-ray. But it does not use any x-ray beams or radiation. Instead, it uses a magnetic field to see the inside of the body. This is one of the main benefits of this type of test. Sometimes a dye is put into the veins to see things better. Like a CT scan, this test can make detailed pictures of the inside of the body. However, you must lay in a tube for this test. Sometimes people with a fear of tight spaces (claustrophobia) can find it scary. It also can take longer than a CT scan. One benefit is that an MRI can see the liver much better than an ultrasound can. It can tell the difference between a cyst, a benign tumor and a cancer in the liver. MRIs are also used at the bottom of the abdomen called the pelvis. It can see a tumor in the rectum in detail or confirm if sinus tracts (fistulae) are around the anus. An MRA can see the arteries to the digestive tract in detail. This can be done instead of a CT when low blood flow to the digestive tract is possible. Another reason is to see if the blood vessels to the intestines are narrowed or blocked.
Magnetic Resonance Cholangiopancreatography (MRCP)
A special kind of MRI called an MRCP can see the bile ducts and pancreas very well. This is used to see if there are any stones in the bile ducts. It can also see if there are cysts in the pancreas.
Magnetic Resonance Enterography (MRe)
An MR enterography is another way to see the small intestine in detail. This is used to look for any irritation that can be from a condition called Crohn’s disease. Like the CT enterography, a large amount of oral dye is swallowed beforehand. Afterwards, you will lay in a tube while dye is injected into the vein. Irritation, narrowing, scarring and sinus tracts (fistulae) can all be seen with this test as well.
- Nuclear Studies
Gastric Emptying Study
A gastric emptying study is a special type of x-ray called a nuclear study. This test sees how well the stomach can empty food. If the stomach is slow to work, that is called gastroparesis. Another term for this is delayed gastric emptying. When the stomach is slow to empty, nausea, vomiting or feeling full easily are some common complaints. The test begins after eating food that contains a radioactive dye in it, that way the food can light up on the x-ray. This is what makes it a nuclear type of x-ray. Pictures are then taken every hour or so for four hours. At this point most of the food should be gone from the stomach. If there is a lot of food left, this is considered slow. One common cause of this is diabetes or high blood sugar. Certain medications or surgeries can cause it as well. Other times there is no answer.
Cholescintigraphy (HIDA Scan)
Another nuclear scan is called cholescintigraphy. The easier name for it is a HIDA scan. This looks at how well the gallbladder works. In this test, radioactive dye is injected into the vein. This dye then goes to the liver where bile is made. It then follows the bile into the gallbladder and then back out and down the bile duct. This test can see if the gallbladder is blocked or inflamed. It can also see if the gallbladder is slow to empty. Other times it can see if bile is leaking out of areas after the gallbladder has been removed.
Positron Emission Tomography (PET) Scan
Positron emission tomography, also known as a PET scan, is like a CT scan. It can see pictures of the inside of the body very well. However, this test is focused on finding cancers. A special chemical called FGD is injected into the vein. This chemical mainly goes to areas that use a lot of energy. Because cancer is fast growing, these cells will light up on the scan. This test is usually ordered to see if cancer treatment has worked. Other times it is done to make sure cancer has not spread. This can see several different types of cancers of the digestive tract. Cancer of the esophagus, stomach, pancreas and colon can all be seen with this test.
Octreotide/Dotatate Scan
An octreotide scan is like a PET scan, except it is used to look for one certain type of cancer called neuroendocrine tumors. Using a special dye into the vein, these tumors can light up on an x-ray. Types of neuroendocrine tumors include carcinoid and gastrinomas. The scan can be used to find the cancer for the first time or used to monitor the cancer.
Tagged Red Blood Cell (RBC) Scan
This test is used to figure out where someone is bleeding. A special dye is injected into the vein that lights up red blood cells. After an hour, many pictures are taken of the abdomen. If any blood is leaking out of the intestines, it will light up on the scan. This test is used if you see blood in your stool, but no one knows where it is coming from. This test can help narrow down which part of the digestive tract is bleeding.
Meckel’s Scan
A Meckel’s diverticulum is a pocket found in the small intestine. This is something you are born with. Usually, it gets found in children at a young age. However, in rare cases it is not found until someone is a young adult. This type of pocket can cause pain or bleeding. This is because a Meckel’s diverticulum is lined with the same cells as the stomach or pancreas. To find the pocket, this scan uses a special dye that is injected into the vein. Once inside, the dye will light up these types of cells. If this type of pocket is found, then surgery may be needed to remove it.
Author(s) and Publication Date(s)
Costas H. Kefalas, MD, FACP, FACG, Northeastern Ohio Universities College of Medicine, Rootstown, OH, and Akron Digestive Disease Consultants, Inc., Akron, OH – Published June 2005. Updated January 2009. Updated December 2012.
Justin A. Crocker, MD, FACG, Duke GI of Raleigh, Raleigh, NC – Updated April 2024.