Investigations and procedures
Barium (contrast) studies
Barium is a radiopaque material that is not absorbed, so when swallowed or used as an enema can be used to delineate the internal markings of the gastrointestinal tract and to assess gut motility. Watersoluble contrast should be used if there is significant risk of leakage of contrast outside the lumen (e.g. if assessing for anastomotic leak).
· X-rays are taken serially following administration of the contrast. Advantages of contrast studies over endoscopic procedures:
· No requirement for sedation, relatively well-tolerated. Motility can be assessed.
· Low risk of perforation, particularly where anatomy is thought to be distorted by previous surgery.
The main disadvantage is lack of ability to biopsy to obtain a tissue diagnosis and to treat, e.g. by removal of polyps or stop gastrointestinal bleeding.
X-rays of the oesophagus are taken as the patient swallows contrast in the erect and prone positions. If assessing for dysphagia, bread may be given with the contrast to demonstrate how solids move through the oesophagus.
Reflux may be seen in the erect or prone position. Diagnoses that may be made include candidiasis, oesophageal webs, pouches, stricture and carcinoma, extrinsic compression and achalasia.
Barium is given together with effervescent tablets; this raises the diagnostic accuracy to 80–90% for peptic ulcer disease as there is an additional contrast between barium and air. Features of a malignant gastric cancer include a protruding mass into the lumen with a crater (ulcer) on its surface, interrupted nodular or irregular folds around a crater and the stiff ‘leather-flask’ appearance (linitus plastica) of diffuse gastric carcinoma (which may be missed on endoscopy).
Barium is swallowed (without effervescent tablets) and X-rays taken as it passes through the small intestine. In both barium meals and follow-through, compression of the abdominal wall may be required to visualise more thoroughly.
Patients are given a low residue diet for 3 days prior to the procedure, with powerful laxatives to cause profuse, watery diarrhoea to clear the large bowel. Barium and air are insufflated into the rectum via a catheter. The patient has to be tipped head-down and rotated to obtain various views of the entire colon, including the terminal ileum in some cases. The procedure can be un-comfortable, unpleasant and requires the patient to be able to stand. Apple-core lesions are classical of colonic carcinoma. Features of colitis can be identified as well as diverticular disease.
In acute illnesses such as possible perforation or diverticulitis, insufflation of air is avoided and a water-soluble contrast is used.