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Andover, MA 01810-6040
In response to a question about performing a barium enema examination in patients who have undergone a failed colonoscopy, Dr. Sat Somers [1] states, "There is no doubt that the barium enema has to be done in double contrast, as it is far superior to a single-contrast examination." I take issue with this statement, and with the implications engendered by its publication in the AJR.
To my knowledge, no consensus exists among radiologists that Dr. Somers' assertion is true. In a recent review article on screening for colorectal cancer, Gazelle et al. [2] state, "Barium enema examination can be performed with either single or double contrast techniques." Even the most vocal proponents of the double-contrast enema acknowledge that "Colonic neoplasms are more difficult to detect in patients with severe diverticulosis, as polypoid lesions may be obscured by overlying diverticula or by circular muscle thickening; this is most common in the rectosigmoid or distal descending colon" [3]. Dr. Somers [1] states, "We have had significant lesions shown on the barium enema that would have been missed if we had used a single-contrast, solid-column method. These were flat, plaque-type early malignancies." In my practice, I am often asked to perform barium enema after failed colonoscopy. Most of these patients have colonoscopy failures because of sigmoid diverticular disease, and I have seen cases of advanced sigmoid colonic adenocarcinomas missed on double-contrast enemas that were clearly and easily visible on follow-up single-contrast examinations.
It would be helpful to the radiology community at large if Dr. Somers clarifies that his response to the question is his opinion only, that there are many ways to "skin this cat" (including CT colography), and that his approach does not constitute the standard of care with respect to colon cancer screening.
References
McMaster University Medical Centre Hamilton, Ontario L8N 3Z5, Canada
I thank Dr. Goldshein for his response to my answer [1]. The consensus among gastrointestinal radiologists is quite clear. Double-contrast barium enema is superior to single-contrast, especially for the detection of polyps and cancer. Single-contrast barium enema has a role in detecting obstruction, if one does not wish to use CT to detect the level of obstruction in an unprepared colon. This group of patients is different from those who test positive for occult blood in the stool and who have undergone a failed colonoscopy.
Dr. Goldshein quotes two articles. The first, by Gazelle et al. [2], does state that the "barium enema examination can be performed with either single or double contrast techniques." The next sentence reads, "Because of its relatively high sensitivity, double contrast barium enema (DCBE) examination is now widely accepted as an effective alternative in colorectal cancer screening." Nowhere do the authors state that the single-contrast examination is as good as the double-contrast, nor is it mentioned again. The remainder of that section only describes aspects of the double-contrast barium enema, and this description is generally positive. In the second article quoted, Levine et al. [3] do state that colonic neoplasms and polyps are more difficult to detect in patients with severe diverticulosis. The article also states, "Careful double contrast technique and meticulous scrutiny of the images therefore are required to optimize detection of these lesions."
Cancers and other notable lesions are missed by radiologists. A study on missed cancers by Kelvin et al. [4] showed that 52% of errors were purely perceptive, 32% were due to a combination of perceptive and technical factors, and 6% were interpretive. In 10% of patients in the study, the lesions could not be seen in retrospect, and the errors were attributed to technical failure (i.e., failure to perform an adequate examination). At four of the six institutions that participated in this study, in only two patients (1%) in 197 cases of primary colorectal carcinoma was the lesion invisible in retrospect, leading the authors to conclude that double-contrast barium enema is highly sensitive.
I do not know how many barium enemas Dr. Goldshein performs in a year or what is his population group; however, in our population of 103 patients [5] with failed colonoscopies, the mean age was 62 years. There were 79 women and 24 men. The most common reason for failure of colonoscopy was previous abdominal or pelvic surgery (55%). The failure rate of colonoscopy recorded by the colonoscopist as being caused in part by diverticular disease was only 12%. This failure was attributed to the patient's having luminal narrowing due to muscular hypertrophy and the colonoscopist's inability to distinguish a diverticular orifice from the bowel lumen, resulting in a reluctance to advance the scope and risk perforation.
CT colonography is certainly an option when colonoscopy fails. This issue was not addressed in my answer to the original question because the question was about performing a barium enema after a failed colonoscopy. CT colonography is coming of age and is good in the hands of a radiologist skilled in this technique who also has access to good equipment and software that optimizes the examination. In fact, CT colonography is ideal for the patient who has undergone a failed colonoscopy and already has an inflated colon, because the examination can be done with the introduction of just a little more air. One need not wait for the sedation to wear off.
Therefore, in summary, double-contrast barium enema is a superior technique, not only in my opinion, but also in the opinion of the authors of the articles cited by Dr. Goldshein, as well as of other gastrointestinal radiologists. The performance of good-quality barium examinations is a dying art. This is manifest by the decline in the number of examinations being performed in radiology and the rapid increase in endoscopic studies. The decline in referrals is due, in many instances, to poor-quality studies and inconclusive reports. Therefore it is important for us to provide the best quality examinations.
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