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Double-Contrast Barium Enema: Use in Practice and Implications for CT Colonography

¹ Department of Radiology, Boston Medical Center, Boston University School of Medicine, 88 East Newton, Atrium 2, Boston, MA 02118.

Received May 26, 2005; accepted after revision July 27, 2005.

 
Address correspondence to J. T. Ferrucci (joseph.ferrucci{at}bmc.org).

Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
OBJECTIVE. This study examines the use and yield of double-contrast barium enemas (DCBEs) for colorectal polyp detection in current clinical practice outside the research setting.

MATERIALS AND METHODS. My colleagues and I retrospectively reviewed adult DCBE studies performed in routine clinical practice at a single academic institution from 2001 through 2004 by reviewing the official radiology and colonoscopy reports. Data were collected on indications for a DCBE, number of positive and negative DCBE reports, results of a DCBE after failed colonoscopy, and professional profiles of the radiologists who performed the DCBEs. Correlation for colon polyp detection was made by reviewing reports of colonoscopy performed within 12 months before or after a DCBE. Polyp detection and matching analysis used a six-segment colon localization scheme.

RESULTS. A total of 244 out of 665 (36.7%) barium enema studies were performed using the double-contrast technique over the 4-year period—that is, approximately one per week. The most common indication for a DCBE (109/244 or 44.6%) was to complete a failed, incomplete, or inconclusive colonoscopy. Overall, only 14 of the 244 (5.7%) studies gave positive reports for polyps, and of these, five were shown to be false-positive at later colonoscopy. Only six polyps 10 mm or larger were positively detected during the entire study, which is approximately one per 60 studies or one every 8 months. In 104 patients who had negative DCBEs after failed or inconclusive colonoscopy, more than 50 subcentimeter polyps had been detected and removed, yet not one additional polyp was detected by a DCBE. Of the 15 radiologists performing the DCBEs during the study period, 89.7% of the studies were done by four individuals. Three of these four radiologists were older than 60 years at the beginning of the study, and two of them are now either retired or no longer perform fluoroscopy.

CONCLUSION. In our center, a DCBE is a low-yield procedure for detecting polyps, with a high false-positive rate, and is not likely to be performed by experienced practitioners in the future.

Keywords: barium • colon • colonoscopy • CT colonography

Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Approximately 12 million adults in the United States alone become eligible for colon cancer screening each year by virtue of reaching the age of 50 years. That number is an order of magnitude greater than those eligible for lung cancer screening, and the likelihood of preventing cancer-related death is more certain. Double-contrast barium enema (DCBE) is one of four tests (along with fecal occult blood, flexible sigmoidoscopy, and colonoscopy) widely accepted for colorectal cancer screening. It is reimbursed by Medicare for colon screening in asymptomatic individuals. Yet the continued use of the DCBE for detecting colorectal polyps has become an area of increasing controversy. Two recent large prospective clinical trials show the sensitivity of DCBEs to hover at only 50% for so-called significant pol yps—that is, those measuring at least 10 mm in diameter [1, 2]. As a result, nonradiologist leaders in the colon cancer screening community increasingly dismiss the DCBE as an ineffective and obsolete technique [3-5]. At the same time, the newest imaging technology for colon polyp detection, CT colonography (CTC), shows far better performance with 55-96% sensitivity for patients with polyps 10 mm or larger in recent single-center [6-8] and multicenter trials [2, 9, 10]. Yet, at present the DCBE is still retained as an approved colon screening test by major national policy-making agencies [11-13], while the acceptance of CTC for colon screening is being withheld by nonradiologist critics who assert the need for additional confirmatory clinical trials [14-17].

We hypothesized that the pattern of DCBE use and its diagnostic yield for polyps in actual clinical practice might exhibit additional negative features not evident in carefully controlled prospective research trial comparisons of a DCBE with colonoscopy. Because actual practice use patterns of the DCBE were poorer than previously believed, the case for earlier adoption of CTC might become even more compelling. We therefore retrospectively reviewed the use and yield of the DCBE in our general radiologic practice in a single academic institution over a recent continuous 4-year period, 2001-2004.

Materials and Methods

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With institutional review board approval and Health Insurance Portability and Accountability Act (HIPPA) compliance, the radiology information system (RIS) archive in our academic urban medical center department was retrospectively searched for all single- and double-contrast enema clinical patient reports filed between January 1, 2001, and December 31, 2004. Barium enemas performed by the pediatric radiology section were excluded regardless of patient complaint or study indication. Full text reports were viewed electronically, and all DCBE cases were manually transferred to an electronic database and also printed to hard copy for ease of retrieval and further analysis.

For colonoscopic correlation, the institution's endoscopy service database was searched for any colonoscopy procedure performed on a DCBE patient within 12 months before or after the DCBE. Hard-copy printouts of all colonoscopy reports were obtained. Data extraction was performed from review of official reports only with no specific reference to images from either examination. For patients with a possible radiographic-colonoscopic correlation, anatomic localization of colonoscopic reach and polyp matches used a six-segment colon nomenclature system (rectum, sigmoid, descending, transverse, ascending, and cecum). The total number of colonic segments visualized (and not visualized) at colonoscopy was recorded. Polyp matches were made using a standard manual algorithm [9]. A polyp match was accepted when the polyp was located in the same or adjacent colon segment and measured within 50% of linear diameter reported on both studies. The database included indications for DCBE, number of positive and negative DCBE reports sorted by polyp size, and results of DCBE after failed or incomplete colonoscopy. Data were also collected on the number, age, and professional practice status of the attending staff radiologists performing DCBE studies during the review period.

Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
A total of 665 barium enemas were performed on adult patients over the 4-year period (2001-2004), of which 244 (36.7%) used the double-contrast technique. Single-contrast enemas were more likely to be performed in elderly or infirm patients, those with a specific postoperative or posttraumatic anatomic question, or those requiring an interpreter. The average age of DCBE patients was 51 years (range, 21-84 years), and patients were more often women by a ratio of 2.6/1 (women/men). The average number of DCBEs per year was 61, only slightly more than one per week. For comparison, our department performed an average of more than 400 CT scans per week during the same 4-year period. There was almost no variation in volume of DCBEs during the 4 years; 61 were done in 2001 and 58 in 2004, although the total volume of all colon enema examinations did decline from 191 for the year 2001 to 137 for the year 2004.

Indications for the DCBE examinations in the 244 patients in this study are given in Table 1. The patient population also fitted the definition for high risk for colorectal neoplasia in that they were unselected adults with colorectal symptoms. The most common indication was for completion of colonoscopy, which accounted for 109 of the 244 (44.6%) DCBE patient referrals. Specific indications for patient referral for a DCBE for completion of colonoscopy are given in Table 2. The most common indication was incomplete or failed endoscopic examination, which occurred in 62 of 109 (56.8%) patients, most commonly because of lumen stricture, redundancy, or unstable vital signs during the procedure. Poor colon preparation, a finding of multiple polyps, and physician choice were additional frequent reasons for referral for radiologic DCBE examination. Scheduling of DCBE examination appointments after failed or incomplete colonoscopy followed routine outpatient procedures and included a standard complete second colon preparation.

Overall, DCBE gave positive results for polyps in 14 (5.7%) of the 244 patients (Table 3). In this subgroup, four patients having a DCBE had both an inconclusive prior colonoscopy and colonoscopy after the positive DCBE report. In one other patient, the DCBE was done to confirm the finding of a 3.0-cm cecal mass seen at colonoscopy 3 months earlier. In these 14 patients with positive DCBE reports, correlation with colonoscopy results also disclosed four additional polyps (DCBE false-negatives), of which one was larger than 10 mm in diameter. Overall, there were nine true-positive reports of polyps and five false-positive reports. Thus, the true-positive rate for detection of any polyp by a DCBE was 3.7%. For polyps 10 mm or greater in diameter, there were six true-positive and three false-positive reports (sensitivity 85.7%, specificity 57.1%). For polyps less than 10 mm, there were three true-positives and two false-positives (sensitivity 50%, specificity 71.4%). For the entire 4-year study period, six 10-mm or larger significant polyps were detected by a DCBE—that is roughly one found every 8 months. However, two patients had false-positive findings that were polypoid masses of 3-4 cm in diameter.

Analysis of the 109 patients referred for a DCBE for completion of colonoscopy showed that five (4.5%) had positive reports on a subsequent DCBE. Three of these were true-positive reports; the other two were false-positive, both of which were false reports of polypoid lesions greater than 1.0 cm in diameter. The remaining 104 patients (94.5%) had totally negative DCBE reports. In this subset of patients, segmental analysis of colon coverage revealed that 370 of a possible 654 segments (56.5%) had been visualized at colonoscopy. In this aggregate of visualized colon segments, colonoscopy detected 39 polyps of less than 6 mm and eight polyps 7 mm or larger; all were removed. Three patients also had findings of polyps described as multiple, several, or a few, most of which were also removed. In the remaining 284 (43.4%) colon segments not seen at colonoscopy and potentially visible with a DCBE, not a single additional polyp was reported.

During the 4-year period, 15 attending staff radiologists performed the DCBE examinations (usually supervising residents). Of the 244 examinations, 219 (89.7%) were performed by just four individual attending physicians, and seven other radiologists performed only a single study each. Of the four staff radiologists performing most studies, three were older than 60 years at the beginning of the study period; one has since retired, one has partially retired, and one is no longer performing gastrointestinal fluoroscopy. There was no attempt to measure the diagnostic performance of individual radiologists because the sensitivity of the negative DCBE studies could not be determined.

Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
This study documents the present clinical use pattern and diagnostic yield of the DCBE in an uncontrolled clinical practice outside the research setting. It thus addresses a common theme of technology assessment models— namely, the availability and usage characteristics of a given procedure at the community level. It is also as much a quality assurance and practice management study as it is clinical science.

The major finding of this study was the very low yield of DCBEs for the detection of colon polyps. Overall, 230 of the 244 (94.3%) DCBE studies gave negative results for polyps. Of these, there were just nine patients (3.7%) with true-positive reports, and only six polyps greater than 10 mm were found over the 4 years (2.4%); that is just over one large potentially significant polyp found every 8 months or every 61 cases. Polyps measuring 10 mm or greater in diameter are now generally accepted as a critical target for detection and removal in colon cancer prevention strategies [18, 19]. However, our 2.4% prevalence of advanced adenomas is considerably lower than that reported in other studies, which have ranged from 10.5% in a large colonoscopic survey study by Leiberman et al. [20] to 4.5% in a multicenter CTC study of average-risk subjects by Pickhardt et al. [9]. Undoubtedly our low prevalence of larger polyps was in part because 109 of the 244 patients (44.6%) having a DCBE had undergone a prior recent colonoscopy. In addition, the mean age of our patient population (51 years) was approximately 10 years younger than that of the Leiberman et al. study population, which could have also lowered our prevalence of large adenomas. Conversely, there were three false-positive reports for polyps greater than 10 mm during the study period, two of which were reported as measuring more than 3 cm in diameter. This gave a very discouraging specificity of 57.1%. Although there are no modern studies on the specificity (false-positive rate) of a DCBE, among the key features of a desirable screening test is a high specificity, ideally more than 95%. Radiologists reviewing DCBE studies are rarely troubled by the risk of interpreting a questionable filling defect as a possible polyp, but in the context of appropriate clinical management false-positive reports may prompt an unnecessary colonoscopy.

This review did not address the broader issue of sensitivity and specificity of DCBEs because patients with negative or positive "possible stool" DCBE results were not generally subjected to colonoscopy. Our aim was not to document the true diagnostic performance of DCBEs, but rather to study only the clinical yield of negative and positive DCBE results. However, in the 14 patients with positive DCBE reports who did undergo confirmatory colonoscopy, four additional polyps were detected, including one larger than 10 mm, which became DCBE false-negatives. However, in the 109 patients who had a DCBE for completion of colonoscopy, at least 50 small (< 10 mm) polyps were found and removed from the 56.5% of the lumen surface inspected at the initial endoscopy. Not one additional polyp was found by a DCBE on the remaining 43.5% of mucosal surface at risk.

The low volume of DCBE studies recorded during our study is likely to drop further in the near future. Until recently health insurers did not reimburse CTC procedures, and for many patients with a failed, incomplete, or inconclusive colonoscopy a DCBE was the only option. In mid 2005, several months after the end of our study period, our local Medicare carrier began to reimburse for CTC after a failed or incomplete instrument colonoscopy. It is likely that many of these patients, 45% of all DCBE volume in our series, will now be preferentially referred for CTC. During the 6 months after the end of the study period, January-June 2005, only 13 DCBE studies were performed at our facility.

There are additional clinical reasons to favor a shift from using the DCBE to using CTC. The residual colonic air distention present after a failed colonoscopy may be an impediment to a successful immediate follow-up DCBE on the same day, but it is a benefit for an immediate follow-up CTC because the requisite gaseous distention is already present. Indeed, our departmental appointment scheduling facility now routes all referrals for failed or incomplete colonoscopy to CTC rather than a DCBE and offers immediate same-day, single-prepare CTC service for patients who want it. Patient preference studies are also discouraging for the DCBE. In two recent questionnaire studies of comparative preference among the three alternative colon cancer screening tests—CTC, optical colonoscopy, and DCBE—patients ranked the DCBE a distant last [2, 21].

The career attrition of senior general or gastrointestinal radiologists evidenced in our data is a further factor that could accelerate the shift away from the DCBE. Not only will there be reduced clinical experience to perform such studies in the future, but resident trainees will have neither the volume nor the teachers available to help them master the needed skills.

Availability to the public is a final key criterion to assess effectiveness of a broad-based population screening test. Healthy asymptomatic individuals are unlikely to find a DCBE available in their local private ambulatory imaging center. However, because CTC is usually performed without drugs, injections, or contrast agents, it is much more suitable for the outpatient imaging center environment and may be performed even without a radiologist present.

This study has several limitations. It is a retrospective observational study only and lacks the rigor of a prospective controlled trial. The data reflect the experience of only a single center and a small group of radiologists and colonoscopists. This may have resulted in bias in patient selection and physician practice patterns. For example, the relatively young median age of our patients (51 years) and the high percentage of single-contrast enema studies (63.3%) reflects the disease mix of our urban inner-city academic center patient population—that is, medically underserved, complex and compromised, and non-English speaking. The polyp-matching algorithm used in the data analysis relied only on comparison of the official written medical radiology and endoscopy reports and did not reference the study images directly. Thus, the specific identification and correlation of individual polyps were not visually confirmed.

The reason for examining the current performance of the DCBE lies in its relationship to CTC as the colon imaging method of preference, which on the basis of evidence the specialty of radiology elects to perform, promote, and defend. Approval for CTC, already a far more effective test with much more potential appeal to the public, is being heavily critiqued and contested by nonradiologists [14-17]. Ordinarily, an established, venerable test would be allowed to discretely fade out of use, but retention of the DCBE on approved national colon screening guideline lists enables nonradiologists to delay the dissemination of the more threatening, competitive CTC technology. If, as we suspect, our poor experience with the DCBE applies to other practices, its era is over. More importantly, updates to national colon cancer screening guidelines to include CTC should be sought sooner rather than later to reflect these practice realities.

References

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