studies are better than endoscopy at demonstrating the anatomic findings in gastroesophageal reflux disease after anti-reflux surgery. barium fluoroscopic examinations have some advantages over computed tomography and magnetic resonance techniques, such as higher spatial resolution and the ability to examine bowel peristalsis and distension in real time. many infections and parasitic infestations produce patterns of the luminal surface, which are best seen on barium examinations. certain parasites are seen as filling defects outlined by barium and barium examinations play an important role in the diagnosis of intestinal infections and infestations as compared to other techniques. barium studies show tapeworms and roundworms as thin, linear filling defects of the bowel. because roundworms have a developed alimentary tract, barium may outline the parasites' intestinal tracts on delayed images. in strongyloidiasis barium studies show intestinal wall oedema, thickening of intestinal folds with flattening, and atrophy of the overlying mucosa. schistosomiasis caused by infection with flatworms have an appearance resembling colitis ulcerosa, with inflammatory polyps, ulcers, fibrosis, wall thickening, loss of haustration, and stenosis in barium x-rays. anisakiasis is demonstrated by barium x-rays as bowel wall oedema, thickening, ulceration, or stricture due to inflammation. sometimes worms are seen as long, thread-like, linear filling defects up to 30 cm long. in typhlitis barium studies show oedema, ulceration, and inflammation of bowel wall resulting in wall thickening. in pseudomembranous colitis, barium studies show pancolitis with thumb printing and shaggy margins as well as plaque-like eccentric, nodular or polypoid appearance. barium studies and computer tomography are the most common tools used to diagnose gastrointestinal lymphoma. barium contrast is more sensitive in the demonstration of subtle mucosa and sub-mucosa abnormalities but computer tomography is the method of choice for determining the extent of disease and staging as well as related complications such as fistulation and perforation. submucosal nodules or masses form a bull's-eye or target appearance on barium studies. adverse effects barium in the lungs resulting from aspiration during a barium swallow 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 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.