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Gastrointestinal Imaging |
1 From the Intestinal Imaging Centre (S.A.T., S.H., V.G., S.M., P.B., C.I.B.) and Cancer Research UK Colorectal Cancer Unit (S.H., W.A.), Level 4V, St Mark’s Hospital, Watford Rd, Northwick Park, Harrow, Middlesex HA1 3UJ, England. Received September 20, 2002; revision requested November 26; final revision received February 5, 2003; accepted March 10. S.A.T. supported by a research fellowship from the Royal College of Radiologists and by GE Medical Systems, Slough, England. Address correspondence to S.H. (e-mail: s.halligan@ic.ac.uk).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: One hundred thirty-six subjects undergoing CT colonography were randomized to receive either 20 mg or 40 mg of hyoscine butylbromide or no spasmolytic. Subjects were also independently randomized to undergo CT colonography with an inflatable rectal balloon catheter or a standard thin rectal tube. Multi–detector row CT colonography was performed with patients in prone and supine positions, with colonic segmental distention assessed by a single observer with a four-point scale. A simple assessment of whether distention was adequate for clinical interpretation was also made, and the effect of hyoscine butylbromide and catheter use was examined by using multivariate ordered logistic regression.
RESULTS: Administration of hyoscine butylbromide was associated with significantly improved cecal (P = .05), ascending (P = .001), and transverse (P < .001) colonic distention when patients were supine and improved ascending (P < .001) and descending (P < .001) colonic distention when patients were prone. Compared with control subjects, patients given a spasmolytic had odds of 6.49 for clinically adequate distention throughout all colonic segments (P = .001). There was no incremental advantage with use of a 40-mg dose. In contrast, rectal balloon catheter use was not significantly associated with improved distention.
CONCLUSION: Hyoscine butylbromide improves colonic distention during CT colonography and should be routinely administered where it is available. Use of a thin rectal tube for insufflation is adequate.
© RSNA, 2003
Index terms: Catheters and catheterization • Colon, CT, 758.1211
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Although the use of glucagon in double-contrast barium enema examinations is well established, investigators have found no benefit to its use during CT colonography (2,4). In Europe, hyoscine butylbromide is preferred to glucagon and is widely administered before CT colonography, although the efficacy of hyoscine butylbromide has not been proved. Hyoscine butylbromide is, however, not licensed in several countries, including the United States, and although it is much cheaper and probably safer than glucagon, it is not without side effects and may precipitate glaucoma, cardiac ischemia, and urinary retention in some patients (5). Furthermore, minor side effects such as dry mouth and blurred vision are common and limit activities; it is recommended that patients not drive immediately after administration. Moreover, authors of recently abstracted work (6) have questioned the advantage of hyoscine butylbromide for CT colonography, while others have suggested that its benefit is most evident when larger doses than those used for double-contrast barium enema examinations are administered.
There is also no consensus as to the best type of rectal catheter to use for CT colonography (the type of rectal catheter can also influence colonic distention), and some investigators argue that an inflatable self-retaining balloon catheter inhibits colonic decompression during the procedure. However, balloon catheters are more expensive than thin rectal tubes, cause more pain when inserted, and have been associated with rectal perforation when used during double-contrast barium enema examinations (7). Interventions such as the use of spasmolytics and specialized catheters add to the complexity, cost, and potential complications of CT colonography, and any benefit must be sufficiently large to outweigh these disadvantages. Thus, the purpose of our study was to investigate the effects of hyoscine butylbromide and an inflatable rectal balloon catheter on luminal distention during CT colonography.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Randomization
Patients underwent CT colonography on the morning of their subsequent colonoscopy and were randomized (by using a computer-generated random-number table created specifically for this study [Arcus Quickstat Biomedical 1.2; Research Solutions, Cambridge, England]) to undergo CT colonography with one of two rectal tubes for colonic gas insufflation. Seventy subjects were randomized to undergo colonography with an inflatable rectal balloon catheter (Trimline DC; E-Z-Em, Westbury, NY), and 66 patients were randomized to undergo colonography with a standard thin rectal tube (14-F Jacques Nelaton rectal catheter; Rusch, Bucks, England) (Fig 1).
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At the completion of the trial, 40 subjects had received no spasmolytic, 66 had received 20 mg of hyoscine butylbromide, and 30 had received 40 mg of hyoscine butylbromide. Three patients who had been randomized to receive hyoscine butylbromide had contraindications (two had recently symptomatic ischemic heart disease and one was being evaluated for glaucoma) and were therefore entered into the no-spasmolytic group. All patients underwent same-day endoscopy after CT colonography and were medically supervised for a prolonged period after CT. The endoscopy admission note and nursing notes were inspected for all patients in an attempt to detect any delayed reactions to the CT colonographic examination.
CT Colonography
CT colonography was performed as follows: All patients maintained a clear liquid diet for 24 hours before the procedure, and, the day before the procedure, 44 patients took sodium picosulphate/magnesium citrate (Picolax; Ferring Pharmaceuticals, Berkshire, England) as a laxative while 92 patients took magnesium citrate (Citramag; Pharmaserve, Manchester, England) supplemented with one sachet of senna granules (Reckitt Benckiser Healthcare, Hull, England).
Each patient randomized to receive hyoscine butylbromide lay supine on the CT table while a 22-gauge intravenous catheter was inserted into an antecubital fossa vein. This catheter was left in situ for sedative administration during subsequent conventional endoscopy. Twenty milligrams of hyoscine butylbromide was then administered for approximately 30 seconds. Patients were then asked to lie in the left lateral decubitus position, and, after a digital rectal examination had been performed to exclude the presence of any low lesions, the rectal tube that each had been randomized to receive was lubricated and inserted.
If a rectal balloon catheter had been allocated, the balloon was gently inflated with the proprietary inflation bag to a volume of approximately 30 mL. If a thin rectal tube had been allocated, it was taped to the patient’s buttocks so that it would not be dislodged. No patient gave a history of distal colitis, which would have been a relative contraindication to use of an inflated rectal balloon catheter. All tubes were left in situ for the duration of the examination.
Carbon dioxide was used for colonic distention in all patients and was introduced by manually squeezing an enema bag (E-Z-Em enema bag; E-Z-Em) that had previously been filled with approximately 2,500 mL of gas and was attached to the rectal tube. In an effort to ensure adequate distention of the right colon, gas insufflation was initiated with the patient in the left lateral position. Palpation of the abdomen during insufflation was performed to help confirm distribution of gas to the right colon before patients were asked to turn to the prone position, at which point more gas was introduced to achieve distal colonic distention. Gas insufflation was performed gently and slowly during approximately 2–3 minutes and was continued to the point of maximal patient tolerance or until the enema bag was empty. A standard CT scout image was obtained with the patient in the prone position, and more gas was introduced if findings on the scout image suggested that there were areas of colonic collapse. CT scanning was performed, and patients were then asked to turn to the supine position. Once they were supine, patients who had been randomized to receive 40 mg of hyoscine butylbromide received a second 20-mg bolus before any further gas insufflation. To allow for absorption of carbon dioxide, more gas was introduced in all patients when they were in the supine position, and, again to determine if distention was adequate, another CT scout image was obtained before the second scanning pass.
CT scanning was performed with a four–detector-row scanner (Lightspeed Plus; GE Medical Systems, Milwaukee, Wis) by using the following parameters: 1.25- or 2.5-mm collimation, pitch of 6, 120 kVp, 50–100 mA, and 50% section overlap. Images were reconstructed at half the nominal section thickness.
Image Analysis
Image analysis was performed at a dedicated workstation by using proprietary software (Advantage Windows 4.0 and Colonography; GE Medical Systems). A single radiologist with experience at more than 200 CT colonography examinations (S.A.T.) evaluated the data sets by using transverse images and multiplanar reformats as deemed necessary in each individual case. A surface-shaded rendered endoluminal view was available but was not deemed useful for distention assessment and was not routinely used.
For the purposes of this study, the colon was considered to consist of six segments as follows: The rectum was defined as the portion of the colon from the anorectal junction proximally to the level of the acetabular roof, the sigmoid was defined as the portion of the colon proximal to the rectum to the level of the pelvic brim at which the colon did not reenter the pelvis, the descending colon was defined as the portion of the colon proximal to the pelvic brim to the midpoint of the splenic flexure, the transverse colon was defined as the portion of the colon lying between the midpoints of the hepatic and splenic flexures, the ascending colon was defined as the portion of the colon proximal to the midpoint of the hepatic flexure but distal to the ileocecal valve, and the cecum was defined as the portion of the colon proximal to the ileocecal valve.
Distention for each of these six segments was graded on a scale from 0 to 3 by using a system adapted from that of Chen and colleagues (1) and in which a grade of 0 indicated complete collapse; a grade of 1, partial collapse; a grade of 2, reasonable but suboptimal distention; and a grade of 3, optimal distention (Fig 2). Partial collapse (grade 1) was defined as a situation where the thickest portion of the haustral folds measured, on average, more than 4 mm in width and met within the lumen, thereby obliterating a clear central navigation pathway through the segment. Reasonable but suboptimal distention (grade 2) was defined as a situation where there was an easily visible colonic wall with slightly thickened haustral folds that measured, on average, more than 2 mm in their widest portion but did not meet within the colonic lumen and therefore allowed a clear central navigation pathway. Optimal distention (grade 3) was defined a situation where the colonic wall was "pencil-thin" throughout the segment, with thin haustral folds that were less than 2 mm thick throughout their length.
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Statistical Analysis
Statistical analysis was performed by using the distention scores of the single, first observer. The distention score was regarded as a categorical variable and analyzed by using ordered logistic regression. The individual effects of the rectal catheter used and of hyoscine butylbromide were accounted for by means of multivariate analysis. The effects of hyoscine butylbromide and of the rectal balloon catheter were initially evaluated for each individual segment by analyzing the prone and supine data sets separately. The two image data sets were then grouped together, and the effects were reexamined for each segment. Finally, results were combined, and the overall effect of both the rectal balloon catheter and hyoscine butylbromide was determined. In all cases, robust standard errors were used to account for the relative lack of independence between segment distention in the same individual.
Results of logistic regression were expressed as the adjusted odds of a patient’s colonic distention being in the next highest distention category when compared with that in the control group (ie, subjects who underwent CT colonography without the spasmolytic or balloon catheter), and P < .05 was considered to indicate a statistically significant difference. The effect of age (ie, less than 65 years or 65 years and older) and sex on distention was analyzed by adding each separately to the basic logistic regression model, and any interaction between these variables and the presence of a rectal balloon catheter was determined. This analysis was performed for each segment after combining the distention scores assigned with the supine and with the prone image data sets.
The overall adequacy of distention was assessed by using logistic regression with standard errors after the yes-or-no grades for clinically adequate distention for all segments were combined. Interobserver agreement for distention scores was assessed by using the weighted 
statistic. A value less than or equal to 0.2 was considered to indicate poor agreement; a value greater than 0.2 but less than or equal to 0.4, fair agreement; a value greater than 0.4 but less than or equal to 0.6, moderate agreement; a value greater than 0.6 but less than or equal to 0.8, good agreement; and a value greater than 0.8 but less than or equal to 1.0, very good agreement.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Comparison of distention scores between the two independent radiologists yielded a weighted of 0.7 (95% CI: 0.6, 0.77), indicating good agreement (Table 1).
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Administration of 20 mg of hyoscine butylbromide meant that patients were, overall, approximately six times less likely to have at least one inadequately distended segment than those given no spasmolytic: odds ratio, 6.49 (95% CI: 2.65, 15.90) (P = .001). This advantage extended to all six colonic segments, including the sigmoid, where inadequate distention occurred in 10 (25%) of the 40 patients who did not receive the spasmolytic but in 14 (15%) of the 96 patients who received hyoscine butylbromide (Table 5). Once again, there was no significant difference when 40 rather than 20 mg was given (P = .29).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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We found that administration of hyoscine butylbromide resulted in significantly better distention when colonic segments were compared by using an established grading scale. We investigated the effect of the spasmolytic on supine and prone scanning separately not only because this allowed us to describe the effects of administration in detail but also because some investigators still advocate the routine use of single-position scanning alone (11), and in any event, frail or immobile patients may require single-position scanning. We found that use of hyoscine butylbromide resulted in significantly better right and transverse colonic distention when patients were in the supine position. An advantage of similar magnitude was found for the prone position, with the addition of improved descending colonic distention. Our findings clearly suggest that use of a spasmolytic is desirable if one is using a single-position approach.
However, dual positioning is of proved benefit (1–3,16) and is practiced by most radiologists performing CT colonography. Optimal distention alone is insufficient for confident diagnosis; disease on a dependent surface may remain obscured by fluid or retained residue despite a segment being well distended. Dual positioning overcomes this problem because the change in position helps redistribute retained fluid as well as gas. However, this benefit is potentially negated if a segment is collapsed, so good distention in both positions is required to achieve the full benefit of dual positioning. When we combined data for prone and supine imaging, we found a clear advantage in the right and left portions of the colon with the use of hyoscine butylbromide. Moreover, when analysis focused simply on whether or not distention was clinically adequate, there was a highly significant beneficial effect; patients given a spasmolytic were more than six times more likely to have clinically acceptable distention than control subjects, a finding that extended to all six colonic segments.
Previous research on spasmolytic use during CT colonography has mainly concentrated on the administration of intravenous glucagon. Both Yee et al (4) and Morrin et al (2) found that colonic distention was not improved after glucagon administration and no longer advocate its use during CT colonography. Both of these studies involved subjective grading of colonic distention with a method similar to that used in the present study. To our knowledge, no peer-reviewed report of an investigation of the administration of hyoscine butylbromide during CT colonography has been published, although, in contradistinction to the results of the present study, authors of an abstracted work (6) have suggested that hyoscine butylbromide offers no benefit. Interestingly, however, Goei et al (10) found that hyoscine butylbromide, as compared with glucagon, resulted in significantly improved distention during barium enema examination—a finding that concurs with our own.
Repeated doses of hyoscine butylbromide are often administered during conventional colonoscopy and, theoretically, on the basis of previous experience with the barium enema, may also be of benefit during CT colonography. For example, in our experience, we have frequently found the second scanning pass of a dual-position CT study to show a less well-distended colon than the first, particularly in patients who are relatively immobile and/or intolerant of gas insufflation. Hyoscine butylbromide is not licensed to be administered in individual boluses of more than 20 mg, so we decided to administer two separate 20-mg boluses. We were, however, unable to show any advantage with a larger dose. The drug takes effect within 30–45 seconds, and its effect can last up to 15 minutes (17). It seems that the relatively rapid examination times typical for CT colonography, in contrast to those for endoscopic colonoscopy, mitigate the need for a longer duration of action. Indeed, the rapid absorption of carbon dioxide through the colonic wall may be a more important factor in reduced distention in the second position when procedure times are long.
Although there are several relative contraindications to the administration of hyoscine butylbromide, in our study it was deemed necessary to withhold the drug from only three patients who had been randomized to receive it; furthermore, we observed no notable adverse events in any subject. This mirrors the experience with hyoscine butylbromide in double-contrast barium enema examinations, for which its use is widespread in countries other than the United States.
One potential advantage to the use of hyoscine butylbromide not addressed in our study is the possibility of reduced discomfort during colonic distention. Oral anticholinergics have been shown to reduce discomfort during barium enema examination (18), but Goei and colleagues (10) found no such advantage with intravenous hyoscine butylbromide as compared with placebo when a simple three-point scale was used to assess discomfort.
The type of rectal catheter used may also influence the ability to distend the colon, a factor that, to our knowledge, has not been addressed to date. We hypothesized that use of an inflatable balloon catheter would improve colonic distention by inhibiting anal gas leakage. This type of catheter has been associated with a very small but significant risk of rectal perforation (7), so any benefit should be of sufficient magnitude to justify routine use. Although we found a clear trend toward improved distention with a balloon catheter, with greater odds versus data in control subjects in all segments except the sigmoid, this reached statistical significance only for the transverse colon in the prone position. When all distention scores from all segments were combined, there was clear evidence of significant benefit, but this disappeared when analysis was restricted to whether or not distention was clinically acceptable.
Interestingly, we found no evidence of any enhanced benefit to the use of a balloon catheter in women or in older patients, although we did find that the sigmoid colon was significantly better distended in patients 65 years of age or younger. This is almost certainly due to an increased incidence of diverticular disease and smooth muscle hypertrophy in the older age group, although we did not quantify this. Although we made 1,632 separate observations, which would normally result in a power of 98% at a probability value of 5%, power was closer to 80% when the relationship between prone and supine scans in the same patient was accounted for. Therefore, this study was adequately powered. This suggests that the size of any effect of the catheter was small and was certainly smaller than the effect of the spasmolytic.
Because we assessed multiple outcomes, it is possible that some differences, particularly those of borderline significance, in fact arose by chance (type II error). This might explain, for example, the apparent worsening of descending colonic distention in the supine position in those patients who received the larger dose of hyoscine butylbromide. However, many differences were significant at the P < .01 level, and it is extremely unlikely that chance alone accounted for the overall trend of improved distention with hyoscine butylbromide.
In summary, we have shown that administration of hyoscine butylbromide improves colonic distention during CT colonography and significantly increases the number of segments in which distention is adequate for clinical interpretation. There is no advantage to administering a repeat dose. A rectal balloon catheter provides slightly better distention than a thin rectal tube, but the effect is small and the risk of rectal perforation is theoretically increased. We recommend that, where permitted, 20 mg of hyoscine butylbromide be routinely administered for CT colonography and suggest that use of a thin rectal tube is adequate.
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FOOTNOTES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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