Upper gastrointestinal series


An upper gastrointestinal series, also called a barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as barium sulfate mixed with water, is ingested or instilled into the gastrointestinal tract, and X-rays are used to create radiographs of the regions of interest. The barium enhances the visibility of the relevant parts of the gastrointestinal tract by coating the inside wall of the tract and appearing white on the film. This in combination with other plain radiographs allows for the imaging of parts of the upper gastrointestinal tract such as the pharynx, larynx, esophagus, stomach, and small intestine such that the inside wall lining, size, shape, contour, and patency are visible to the examiner. With fluoroscopy, it is also possible to visualize the functional movement of examined organs such as swallowing, peristalsis, or sphincter closure. Depending on the organs to be examined, barium radiographs can be classified into "barium swallow", "barium meal", "barium follow-through", and "enteroclysis". To further enhance the quality of images, air or gas is sometimes introduced into the gastrointestinal tract in addition to barium, and this procedure is called double-contrast imaging. In this case the gas is referred to as the negative contrast medium. Traditionally the images produced with barium contrast are made with plain-film radiography, but computed tomography is also used in combination with barium contrast, in which case the procedure is called "CT enterography".

Types

Various types of barium X-ray examinations are used to examine different parts of the gastrointestinal tract. These include barium swallow, barium meal, barium follow-through, and barium enema. The barium swallow, barium meal, and barium follow-through are together also called an upper gastrointestinal series, whereas the barium enema is called a lower gastrointestinal series. In upper gastrointestinal series examinations, the barium sulfate is mixed with water and swallowed orally, whereas in the lower gastrointestinal series, the barium contrast agent is administered as an enema through a small tube inserted into the rectum.
Barium X-ray examinations are useful tools for the study of appearance and function of the parts of the gastrointestinal tract. They are used to diagnose and monitor esophageal reflux, dysphagia, hiatus hernia, strictures, diverticula, pyloric stenosis, gastritis, enteritis, volvulus, varices, ulcers, tumors, and gastrointestinal dysmotility, as well as to detect foreign bodies. Although barium X-ray examinations are increasingly being replaced by more modern techniques, such as computer tomography, magnetic resonance imaging, ultrasound imaging, endoscopy and capsule endoscopy, barium contrast imaging remains in common use because it offers the advantages of greater affordability, wider availability, and better resolution in assessing superficial mucosal lesions.

Mechanism

Barium sulfate is swallowed, which because it is a radio opaque substance does not allow the passage of X-rays. As a result, areas coated by barium sulfate will appear white on an X-ray film. The passage of barium through the gastrointestinal tract is observed by a radiologist using a fluoroscope attached to a TV monitor. The radiologist takes a series of individual X-ray images at timed intervals depending on the areas to be studied. Sometimes medication which produces gas in the gastrointestinal tract is administered together with the Barium sulfate. This gas distends the gastrointestinal lumen, providing better imaging conditions and in this case the procedure is called double-contrast imaging.

Procedure

Clinical status and relevant medical history are reviewed prior to the studies. Patient consent is required.

Barium swallow

Little or no preparations are required for the study of the larynx, pharynx, and esophagus when studied alone. A thick barium mixture is swallowed in supine position and fluoroscopic images of the swallowing process are made. Then several swallows of a thin barium mixture are taken and the passage is recorded by fluoroscopy and standard radiographs. The procedure is repeated several times with the examination table tilted at various angles. A total of 350-450 mL of barium is swallowed during the process. Normally, 90% of ingested fluid should have passed into the stomach after 15 seconds.

Barium meal and barium follow-through

For barium meal or barium follow-through examinations, a 6-hour period of fasting is observed prior to the studies. Barium is administered orally, sometimes mixed with diatrizoic acid to reduce transit time in the bowel. Metoclopramide is sometimes also added to the mixture to enhance gastric emptying. X-ray images are then taken in a supine position at intervals of 20–30 minutes. Real-time fluoroscopy is used to assess bowel motility. The radiologist may press or palpate the abdomen during images to separate intestinal loops. The total time necessary for the test depends on the speed of bowel motility or transit time and may vary between 1 and 3 hours.

Enteroclysis

In this procedure continuous infusion of contrast into the bowel as well as IV contrast injection take place. Therefore, there will be more significant small bowel distension compared to CT enterography which could cause discomfort for the patient.
For small bowel examinations, in addition to fasting for 8 hours prior to examination, a laxative may also be necessary for bowel preparation and cleansing. Enteroclysis involves the continued infusion of 500 to 1000 mL of thin barium sulfate suspension into the intestine through a duodenal tube. Then methylcellulose is instilled through the tube. Barium and methylcellulose fill the intestinal loops which can be viewed continuously using fluoroscopy, or viewed as standard radiographs taken at frequent intervals. The technique is a double-contrast procedure that allows detailed imaging of the entire small intestine. However, the procedure may take 6 hours or longer to complete and is quite uncomfortable to undergo.

Interpretation of results

Radiographic examinations involve radiation exposure in the form of X-rays. Although barium ions are toxic, their use is generally regarded as safe because the small amounts of barium ions available in solution and absorbed by the gastrointestinal tract are deemed to be negligible; however, isolated cases of barium encephalopathy have been described following absorption of barium from the intestinal tract. Constipation and abdominal pain may occur after barium meals. The formation of baroliths, which may need to be removed surgically, is a complication of the use of barium sulfate. Barium sulfate may cause serious peritoneal irritation. Leakage of barium sulfate into the abdominal cavity may occur in people with duodenal ulcers or other perforations and may lead to peritonitis, adhesion, and granulomas; it is associated with a high mortality rate. Leakage of barium into the mediastinum or peritoneal cavity may lead to endotoxic shock, which is often fatal; as a result, the use of barium as a contrast agent is contraindicated when there is a suspicion or possibility of compromise of bowel wall integrity. Aspiration or inhalation of barium sulfate into the lungs during oral application can lead to serious respiratory complications leading to fatal aspiration pneumonia or asphyxiation. Hypersensitivity and allergic reactions are rare but some additives contained in barium preparations may induce immune reactions. Complete gastrointestinal obstruction is also a contraindication for barium studies.

History

Barium sulfate as a contrast medium was evolved from the prior use of bismuth preparations which were too toxic. The use of bismuth preparations had been described as early as 1898. Barium sulfate as a contrast medium in medical practice was introduced largely as a result of the works of Krause a director of the Bonn Polyclinic, now the medical faculty of the University of Bonn and his colleagues Bachem and Gunther. In a paper read in 1910 at the radiological congress they advocated for the use of barium sulfate as an opaque contrast medium in medicine.