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|Lower gastrointestinal series|
Radiograph of a barium enema displaying a colonic herniation.
A lower gastrointestinal series is a medical procedure used to examine and diagnose problems with the human colon (large intestine). Radiographs (X-ray pictures) are taken while barium sulfate, a radiocontrast agent, fills the colon via an enema through the rectum.
The term barium enema usually refers to a lower gastrointestinal series, although enteroclysis (an upper gastrointestinal series) is often called a small bowel barium enema.
This test may be done in a hospital or clinic. The patient lies on the X-ray table and a preliminary X-ray is taken. The patient is then asked to lie on their side while a well lubricated enema tube is inserted into the rectum. As the enema enters the body, the patient might have the sensation that they need to have a bowel movement. The barium sulfate, a radiodense (shows as white on X-ray) contrast medium, flows through the rectum into the colon. A large balloon at the tip of the enema tube may be inflated to help keep the barium sulfate inside. The flow of the barium sulfate is monitored by the health care provider on an X-ray fluoroscope screen (like a TV monitor). Air may be puffed into the colon to distend it and provide better images (often called a "double-contrast" exam). If air is used, the enema tube will be reinserted if it had been removed and a small amount of air will be introduced into the colon, and more X-ray pictures are taken.
The patient is usually asked to move to different positions and the table is slightly tipped to get different views.
If there is a suspected bowel perforation, a water-soluble contrast agent (such as diatrizoate) is used instead of barium. The procedure is otherwise very similar, although the images will be of poorer quality. If a perforation exists, the contrast will leak from the bowel to the peritoneal cavity; water-soluble material is less obscuring compared to barium should an abdominal incision to remove the contrast be necessary.
Thorough cleaning of the large intestine is necessary for accurate pictures. Test preparations include a clear liquid diet or nothing at all (nihil per os or NPO) after midnight, drinking magnesium citrate or another laxative, and warm water enemas to clear out any stool particles.
Barium enemas are most commonly used to check bowel health; they can help diagnose and evaluate the extent of inflammatory bowel diseases such as ulcerative colitis and Crohn's disease. Polyps can be seen, though not removed during the exam like with a colonoscopy-- they may be cancerous. Other problems such as diverticulosis (small pouches formed on the colon wall that can become inflamed) and intussusception can be found (and in certain cases the test itself can treat intussusception). An acute appendicitis or twisted loop of the bowel may also be seen. If the picture is normal a functional cause such as irritable bowel syndrome (IBS) may be considered.
In a healthy colon, barium should fill the colon uniformly and show normal bowel contour, patency (should be freely open), and position.
Additional conditions under which the test may be performed:
X-rays are monitored and regulated to provide the minimum amount of radiation exposure needed to produce the image. Most experts feel that the risk is low compared with the benefits. Pregnant women and children are more sensitive to the risks of ionizing radiation.
A more serious risk is a bowel perforation.
CT scans and ultrasounds are now the tests of choice for the initial evaluation of abdominal masses, and colonoscopies are becoming the standard for routine colon screening for those over age 50 or with a familial history of polyps or colon cancer, although it is not uncommon for a barium enema to be done after a colonoscopy for further evaluation.