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. 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. 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.