Physics, Techniques and ProceduresBarium enema
radiographic examination of the colon using
barium sulphate suspension as contrast medium. The examination depends heavily of proper bowel preparation. Many regimens exist, most relying on a combination of dietary restriction, purgation and overhydration. The laxatives used usually
act by increasing the faecal water excretion and/or by stimulating colonic peristalsis. Cleansing water enemas are less commonly used due to the deleterious effect of retained water on mucosal coating of the contrast medium. The
barium sulphate suspension is preferably introduced through a closed disposable system. As opposed to administering
barium from an open can, the closed system excludes the possibility of cross-infection and allows rectal drainage whenever needed. It also allows use of an
enema tip with side-arm for air insufflation. The general contraindications for all
barium enema studies are peritonitis, free intraperitoneal air, allergy to
barium suspensions and risk of perforation. The two main examination techniques are single-contrast and double-contrast
barium enemas.
Single-contrast barium enema.
This is the less-preferred method, usually reserved for the following indications: uncooperative, immobile patient, acute mechanical
obstruction, reduction of intussusception, exclusion of gross pathology, and evaluation of the anatomical configuration of the colon. A low density (0.10.2 g/ml)
barium suspension is used for "see-through" effect. The suspension is run in slowly under fluoroscopic guidance, and spot films are taken in several
radiographic views, often combined with manual compression of the colon.
Double-contrast barium enema.
This is the preferred method. The
barium enema is combined with insufflation of air (or alternatively carbon dioxide) for a much better "see-through" effect than the single-contrast method. The
barium suspension should only coat the
mucosa in a thin layer. To enable visualization of fine anatomical detail en face, this requires a higher density of the suspension (usually 0.6-1.1 g/ml). A smooth muscle relaxant (20 mg of hyoscine butylbromide, Buscopan or 0.51.0 mg of glucagon) is often injected intravenously at the beginning of the procedure to relieve possible colonic spasms. A balloon
catheter may be used to prevent leakage from the
rectum. The
barium suspension is usually run in with the patient in the
prone or left lateral position. Infusion is stopped when the
barium column reaches the
transverse colon. Air is then insufflated, the
rectum drained, and the remainder of the colon is filled with
barium and air by air insufflation combined with positional changes of the patient to promote filling by gravity. The examination includes several standard
radiographic views. Remote control units with overcoach tube allowing tube angulation are preferred. Spot films are taken of any
lesion seen fluoroscopically (
Fig.1).
Variations of the main techniques.
The sigmoid flush is a technique used in patients with severe diverticular disease in the sigmoid colon. At the end of a standard double-contrast barium enema, the sigmoid colon is filled with a dilute barium suspension. This improves detection of intraluminal disease in this part of the colon.
The instant barium enema is a "gentle" variation of the double-contrast barium enema used in patients with known colitis where colonoscopy has failed to show the proximal extent of the disease. The examination is started with a plain radiograph to exclude toxic megacolon or perforation. No bowel preparation is required (or advisable) in active colitis. After intravenous injection of a smooth muscle relaxant, the colon is filled with barium suspension to the transverse colon. The rectum is drained and air carefully insufflated, turning the patient as required. Often, one prone radiograph is all that is required to show the extent of colitis. See also water-soluble contrast enema.
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