These studies (tests) use a barium-containing solution that coats the lining of the esophagus, stomach, and intestines. The coating of barium helps find abnormalities of the lining of these organs. These are sometimes useful for the diagnosis of GI tumors. They are least effective in finding small intestine tumors. Barium studies can be used to examine the upper or lower parts of the digestive system. You will probably have to fast and may need to take laxatives and/or enemas to cleanse the bowel the night before or the morning of these exams.

A barium swallow (also known as an upper GI series) is used to examine the lining of the esophagus, stomach, and the first part of the small intestine. Patients getting this test drink a barium solution before the x-ray pictures are taken. A small bowel follow through is a continuation of this test that is sometimes used to look for problems in the small intestine. For this test, x-rays are taken at regular intervals over the course of a few hours as the barium passes through the intestines.

Another option for looking at the small intestine is enteroclysis. In this test, a thin tube is passed from the mouth down through the stomach to the start of the small intestine. Barium contrast is sent through the tube, along with a substance that creates more air in the intestines, causing them to expand. X-rays of the intestines are then taken. This test may be quicker and give more complete results than a small bowel follow through, although placement of the tube can be uncomfortable, even when using medicine to numb the throat.

A barium enema with air contrast (also known as double-contrast barium enema or a lower GI series) is used to look at the inner surface of the large intestine. For this test, the barium solution is given through the anus while the patient is lying on the x-ray table. When the colon is about half full of barium, the patient rolls over so the barium spreads throughout the colon. In addition to barium, air can be blown into the large intestine to help push the barium towards the wall of this organ and better coat its inner surface. X-rays are then taken.

Barium x-rays are used less these days than in the past. In many cases they are being replaced by endoscopy -- where the doctor actually looks into the colon or stomach with a narrow fiber optic scope (see below).

Computed Tomography (CT)

The CT scan is an x-ray procedure that produces detailed, cross-sectional images of your body. Instead of taking one picture, like a standard x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these into images of slices of the part of your body that is being studied.

Often after the first set of pictures is taken, you will get an intravenous (IV) injection of a "dye," a radiocontrast agent that helps better outline structures in your body. A second set of pictures is then taken. You may also be asked to swallow an oral contrast liquid. This helps outline your intestinal tract.

The IV injection can cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Please be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays. You need to lie still on a table, and the part of your body being looked at is placed within the scanner, a cylinder-shaped machine that completely surrounds the table. The test is painless, but you may find it uncomfortable to hold still in certain positions for minutes at a time.

CT scans are useful in patients with GIST to find the location and size of the tumor, as well as to see whether it has spread into the abdomen or the liver.

In some cases, CT scans can also be used to guide a biopsy needle precisely into a suspected cancer or metastatic lesion. However, because of the risks involved (bleeding, possible increased risk of tumor spread), these types of biopsies are usually done only if the result might affect the decision on treatment. (For more information, see the information about biopsy below.)

Magnetic Resonance Imaging (MRI)

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. Not only does this produce cross-sectional slices of the body like a CT scanner, but it can also produce slices that are parallel with the length of your body. A contrast material might be injected just as with CT scans but is used less often.

MRI scans are a little more uncomfortable than CT scans. They take longer -- often up to an hour. You have to lie inside a tube, which is confining and can upset some people with a fear of enclosed spaces. Newer, "open" MRI machines can help with this if needed. The machine also makes buzzing and clicking noises that some people might find disturbing, but many places will provide ear plugs or headphones with music to block this noise out.

MRI scans are useful in GIST to find the extent of the cancer in the abdomen, although usually CT scans are adequate. They are also useful in looking for return of cancer (recurrence) or spread (metastases) to distant organs, particularly in the brain or spine.

Positron emission tomography (PET)

PET scans have become one of the most useful tests for spotting GIST. In PET scanning, low-level radioactive glucose (sugar) is injected into the patient's vein. Because cancer cells use sugar much faster than normal cells, the tumor takes up the radioactive material more quickly. A special camera can then be used to spot the radioactive areas in the body.

This test may be a useful test for staging the cancer as well as for finding out whether a drug treatment is working. (If it is, the tumor will stop taking up the radioactive glucose.)

Newer devices can combine the PET scan with a CT scan for a more accurate assessment of tumor spread and whether it is responding to drug treatment.

Endoscopy

These tests use a flexible lighted tube (endoscope) with a video camera on the end. The camera is connected to a video screen, which allows the doctor to clearly see any masses in the lining of the digestive organs. If abnormal areas are found, small pieces of tissue can be removed through the endoscope (biopsy). The tissue can be looked at under the microscope to find out if cancer is present and what kind of cancer it is.

For upper endoscopy (also known as an EGD), patients are made sleepy (sedated) and a tube is passed down through the mouth to show the esophagus, stomach, and first part of the small bowel.

In a colonoscopy (also known as a lower endoscopy), a long-flexible tube known as a colonoscope is inserted through the anus up into the colon. The colonoscope allows the doctor to see the lining of the entire rectum and colon. This test usually requires that you take laxatives or have an enema beforehand to make sure the bowels are empty. You will be given intravenous medicine to make you feel relaxed and sleepy during the procedure. A colonoscopy may be done in a hospital outpatient department, in a clinic, or in a doctor's office. It usually takes 15 to 30 minutes, although it may take longer if a tumor is seen and/or a biopsy taken.

Unfortunately, neither upper nor lower endoscopy can reach all areas of the small intestine, where some GISTs begin. This can delay finding these tumors. A newer technique, known as capsule endoscopy, may help look at these areas in some cases. For this test, a person swallows a capsule (about the size of a large vitamin pill) that contains a light source and a very small camera. Like any other pill, the capsule goes through the stomach and into the small intestine. As it travels (usually over the course of about 8 hours), it takes thousands of pictures. These images are transmitted electronically to a device worn around the person's waist, while he or she goes on with normal daily activities. The pictures can then be downloaded onto a computer, where the doctor can view them as a video. The capsule passes out of the body during a normal bowel movement and is discarded. This is still a fairly new technique, and its use is still being studied.

When looking into the GI tract with an endoscope, the doctor may see only a bulge under the normally smooth surface if a GIST is present. This is because GIST tumors are often below the lining (mucosa) of the GI tract. Therefore, compared with most cancers, it is much harder to recognize a GIST in the GI. Because many GISTs are below the mucosa (submucosal), a biopsy is hard to obtain through the endoscope. As a result, only about half of GISTs are diagnosed before surgery.

If the tumor breaks through the lining of the GI tract and is easy to see, there is a greater chance that the GIST is cancerous (malignant).

Endoscopic Ultrasound (EUS)

This newer imaging technique is used in some patients having an endoscopy. For this test, the endoscope has a small ultrasound probe on the end that gives off high-frequency sound waves. The probe detects the sound wave echoes that bounce off tissues of the digestive tract wall. A computer then translates the pattern of echoes into an image of the wall of the esophagus, stomach, intestine, or rectum.

In GIST, endoscopic ultrasound can be used to find the precise location of the tumor and to determine its size. It is useful in finding out how far a tumor has spread through the wall of the esophagus, stomach, intestine, or rectum. The test can also help predict whether the tumor has spread beyond the wall of these organs to nearby tissues. In some cases it may be used to help guide a biopsy (see below).

Biopsy

Even if a mass is found on a barium x-ray or CT scan, these imaging tests cannot tell if the mass is a GIST, some other type of tumor (benign or cancerous), or a localized infection (confined to one area). The only way to know for sure is to remove cells from the abnormal area and look at them under a microscope. This procedure is called a biopsy.

There are several ways to take a sample from a GI tract tumor. One way is through the endoscope. When a tumor is found, the doctor can operate a biopsy forceps (pincers or tongs) through the tube to take a small sample of the tumor. Even though the sample will be very small, doctors can usually make an accurate diagnosis. About half the time, the biopsy will not get the cancer because it grows underneath the lining of the intestine or stomach. (The biopsy forceps can't go deep enough.)

Although doctors can pass an upper endoscope into the small intestine, this is generally not a practical way to obtain a biopsy of a suspected GIST, unless it is located in the duodenum, which is the part of the small intestine just following the stomach.

Bleeding from a GIST after a biopsy is rare but can be a serious problem. If this occurs, doctors can sometimes inject drugs that constrict blood vessels through the endoscope into the tumor to stop the bleeding.

In some cases, a fine needle biopsy may be used to get a sample of a tumor. In these biopsies, a doctor places a thin, hollow needle into the tumor based on guidance from imaging tests such as a CT scan or endoscopic ultrasound. These types of biopsies must be done carefully and are usually done only if they will help determine treatment options, because doctors are concerned they may cause bleeding or possibly increase the risk of cancer spreading.

If a sample can't be obtained from an endoscopic or needle biopsy or if the result wouldn't affect treatment options, a doctor may recommend waiting until surgery to get a sample of the tumor. This is done in an operation called a laparotomy, where the doctor creates an opening in the abdomen to reach and remove the tumor directly.

Once a tumor sample is obtained, a doctor who specializes in lab tests ( a pathologist) looks at it under a microscope. Although the pathologist may suspect that a tumor is a GIST, he or she can't be sure without a special test called immunohistochemistry.

In this test, a part of the sample is treated with special manmade antibodies that will attach only to the KIT protein (also called CD117). The antibodies cause color changes if the KIT protein is present, which can be seen under a microscope. Because most GIST cells contain this substance but cells of most other types of cancer do not, this test can be useful in determining whether a GI tumor is a GIST or not.

Blood Tests

Your doctor will likely order several blood tests if he or she thinks you may have a GIST. A blood count can tell whether you are anemic (have a low red blood cell count). Some people with GIST may become anemic because of bleeding from the tumor.

Other blood tests can measure your liver function. If the results of theses tests are abnormal, it may mean that the GIST has spread to your liver.

There are no blood tests that can detect GIST cancer cells in the blood. These tumors do not release any known substances in the blood that can be used as markers to measure the response of a GIST to treatment.