Double contrast barium enema technique
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Double contrast barium enema (DCBE) technique is a method of imaging the colon with fluoroscopy. "Double contrast" refers to imaging with the positive contrast of barium sulfate contrast medium (rarely water-soluble iodinated contrast) as well as with the negative contrast of gas (CO2 preferable). An exam with only a positive contrast agent is considered a single contrast barium enema.
The double contrast technique is preferred over the single contrast technique when one wants a better visualization of the mucosa. In the past it had been used for colon cancer (e.g. polyp) screening 2, especially as a follow-up for failed colonoscopies, but CT colonography has effectively replaced it for that role 3.
Single contrast barium enema is usually sufficient for fistula or postoperative leak evaluation 2.
There are few contraindications:
suspected colonic perforation 1
imminent rectal biopsy within 7 days of procedure or within 7-10 days after the rectal biopsy 1
documented history of anaphylaxis to barium
The patient should be relatively mobile (e.g. should be able to turn quickly) in order for a double contrast barium enema to be successful. A known left colon narrowing is a relative contraindication as barium may become trapped upstream from the partial obstruction and become rock hard. Acute diverticulitis is a relative contraindication as well.
As a double contrast barium exam is meant to examine the colonic mucosa, a bowel preparation (prep) is indicated. Bowel prep strategies are institution-dependent 1. If the patient cannot tolerate a bowel prep, then the rationale for the exam should be reconsidered. Patients with a left-sided colonic lesion may have difficulty with bowel prep and consideration should be given to cleaning enemas and rectal suppositories.
rectal tube (e.g. Miller) for administration of contrast
the Miller tube has three components
a (wide bore) tube for administration of barium
a (usually blue) tube for administration of gas (usually through manual insufflation)
a smaller tube for inflating the balloon at the tip
adhesive tape is often useful to tape the tube to the patient and prevent it from backing out
enema bag and IV pole
One of the most important considerations for a barium enema is the density and viscosity of the barium. Ideally contrast should be dense enough to coat mucosal lesions. If it is too dense however, then not only will the fluoroscopic tube potentially "burn out" the background image and obscure overlapping loops, it may obscure smaller (and sometimes large!) colonic lesions. Where this optimal density lies is dependent on one's fluoroscopic equipment and available contrast solutions. In general, 100% w/v is not a bad target.
Water-soluble contrast is not usually indicated for a double contrast exam as it does not coat the mucosa as well as barium (converse applies for a CT colonogram). If there is a concern for leak, then a single contrast study is usually indicated. It could be considered for cases of barium allergy or left colon obstructing lesion, but given the poor coating of water-soluble contrast, one should reconsider whether it is worthwhile to perform the study.
Some radiologists may premedicate the patient with an anti-peristaltic agent before the exam to relax the colon 3, but this is not mandatory. Main agents employed are hyoscine butylbromide or glucagon 1. Both can be given IV or IM. Subcutaneous injection is usually avoided.
The patient should be in the left lateral decubitus position at the beginning of the exam, with the knees bent, in preparation for placement of the rectal tube. Visually inspect the anus before inserting the tube, to ensure that the balloon will not be inflating against an obvious abnormality (e.g. large varices, inflammatory bowel disease, carcinoma, sinus tract, etc.).
A thin layer of lubricant is spread onto the enema tube tip before insertion. Lidocaine may help to reduce pain in hemorrhoids and inflammatory conditions. Large bore Foley's catheter may be used if there is difficulty in inserting the Miller's tube 1.
Digital rectal examination may also be useful to assess sphincter tone, thus to determine whether balloon catheter inflation is needed to retain the rectal tube. Most patients however, are able to retain the catheter with encouragement and routine inflation of the retention balloon is unnecessary 1. Any hemorrhoids, masses, and inflammatory conditions may also be assessed during digital rectal examination as inflation of the retention balloon risks rectal tear, abrasion, and increases the risk of hemorrhoidal bleeding 1.
The balloon is usually only inflated after normal distal rectum is demonstrated on fluoroscopy and patient is expelling barium and air from anal canal 1. If the patient has trouble holding the balloon in the rectum (and assuming there is no obvious rectal/anal problem such as severe proctitis or tumor), then the balloon on the enema tip can be inflated to keep the tube in place.
Patients who have a history of pelvic irradiation, rectal ulcer, distal rectal mass, suspected rectovaginal fistula, or previous anal canal surgery may not be suitable for balloon catheter inflation 1.
The following is one technique for a generic double contrast exam. If the exam is for evaluation of a known lesion or for a targeted area, it can be modified (e.g. right colon only for an incomplete colonoscopy).
Scout (if indicated) views are shown below:
left lateral pelvis
with the patient in the prone position, barium is slowly administered until it reaches the mid-transverse colon.
after it reaches this point, drain the barium from the distal rectosigmoid and rectum.
begin manual gas insufflation
sigmoid colon (important to get these first before contrast potentially reaches the right colon)
hepatic flexure, erect LPO
distal ascending colon, erect LPO
mid transverse colon, erect or supine
splenic flexure, erect RPO
proximal descending colon, erect RPO
rectum, tip out
terminal ileum, LPO, if there is a question of inflammatory bowel disease
Supplemental overhead radiographs are also useful
prone cross table lateral of the rectum
prone caudally-angled rectosigmoid
the degree of gas insufflation is important
too little gas, it will be difficult to identify polyps
too much gas will potentially flatten colonic lesions and may cause the patient discomfort
the amount of gas to use will depend on the patient and the clinical situation - it is something often learned with experience
other than the early sigmoid spot radiographs before the right colon fills, the order of spot radiographs is not important, but be sure to get an image of each part of the colon
constricting "lesions" may be colonic spasm
if you see an area that may be a constriction, come back to image it later to see if it has opened up
indication for routine preliminary radiograph of the abdomen scout is dependent on local policy. In some centers, all inpatients and outpatients with a history of gastrointestinal surgery or clinical history suggestive of bowel obstruction, perforation, inflammatory bowel disease, fistula, abscess or suspicions of inadequate bowel preparation undergo preliminary radiograph of the abdomen 1
Patients may return to a normal diet, but should be warned that they are likely to find white barium material in their stools for a day or two, and maybe mildly constipated, so should aim for a high fluid intake (ideally water).