©2010 Taipei Medical University
O R I G I N A L A R T I C L E
Background: High-attenuation oral contrast agents in the form of iodine solutions or bar-ium suspensions have been used traditionally and effectively for abdominal computed tomography (CT) examinations. Apart from the unpleasant taste, there are relatively few disadvantages that may affect interpretation, such as pseudotumor formation due to incomplete mixing of contrast material with the bowel contents and poor mural discrimi-nation. Thus, low-attenuation oral contrast materials are needed.
Purpose: The aim of this study was to evaluate the efficiency of whole milk as a low-attenuation contrast agent compared with water-soluble contrast medium and water for abdomi-nopelvic CT.
Methods: A total of 152 patients were randomly assigned to receive whole milk (4%), water or water-soluble contrast medium (Optiral). All CT scans were performed using a 64-multidetector CT scanner with a 0.35-second rotation time. Two radiologists were respon-sible for reviewing the images to assess bowel wall enhancement and bowel dilation. Results: There were no differences in average dilation scores among the three groups for duodenum and jejunum. The average dilation score in the milk group was higher than that in the water-soluble contrast medium group in the antrum, and there was no difference between water and milk. For the ileum, there were no differences in the average dilation scores in the milk and water-soluble contrast medium groups, and milk produced better dilation compared with water. Bowel enhancement in the water and milk groups was stronger than that in the water-soluble contrast medium group. The major side effects of milk were nausea and flatulence.
Conclusion: We concluded that abdominopelvic multidetector CT with whole milk pro-vides better bowel dilation and wall visualization compared with high-attenuation contrast medium. Whole milk and water have potential as good oral contrast materials for bowel discrimination. However, whole milk should be considered as an alternative to water in cases of disease suspected in the pelvis.
Received: Oct 22, 2009 Revised: Mar 4, 2010 Accepted: Apr 28, 2010 KEY WORDS: abdominal computed tomography; multidetector computed tomography; water-soluble contrast medium; whole milk
Depiction of Bowel Wall Visualization and
Dilation in Abdominopelvic MDCT:
Comparison of High-attenuation
Contrast Medium, Water and Whole Milk
Ching-Huei Kung
1, Hung-Jung Wang
1, Ting-Kai Leung
1,2, Yi-Hsiang Lin
1,
Ya-Yen Chen
1, Chi-Ming Lee
1,2*
1Department of Diagnostic Radiology, Taipei Medical University Hospital, Taipei, Taiwan 2Department of Medicine, Taipei Medical University, Taipei, Taiwan
*Corresponding author. Department of Diagnostic Radiology, Taipei Medical University Hospital, 252 Wu Hsing Street, Taipei 110, Taiwan. E-mail: [email protected]
1. Introduction
High-attenuation oral contrast agents in the form of iodine solutions or barium are used during abdominal and pelvic computed tomography (CT) scans to localize and identify bowel loops, and to distinguish bowel from other structures.1 However, when the gastrointestinal tract is not consistently opacified or the gastrointesti-nal tract wall is obscured by adjacent high-attenuation contrast media, interpretation of images can be ham-pered.2 Raptopoulos et al3 reviewed 400 abdominal CT scans and noted poor mixing of an iodinated oral con-trast agent with the contents of the gastrointestinal tract in 26% of cases, and intestinal pseudotumors, which require additional scanning, were seen in an additional 11% of cases.
Low-attenuation contrast media have been used to overcome the problems encountered with high-attenuation contrast media. Horton et al4 demonstrated that low-attenuation contrast media is an ideal CT oral contrast because it is relatively nonabsorbable and of low risk to patients if aspirated. It can also be easily ti-trated to create the desired density. The possibility of using low-attenuation contrast medium as an oral contrast was first reported in the 1980s by Cohen et al who de-scribed the successful use of metrizamide as an oral con-trast agent in neonates.5 To date, multiple low-attenuation oral contrast agents have been studied, such as air, water, corn oil or metoclopramide hydrochloride, and polyethylene glycol.6,7 However, not all of them are acceptable or affordable.
Thompson et al8 demonstrated that whole (4%) milk is an effective low-attenuation oral contrast agent for abdominal helical CT. They found that this effectively slows passage through the upper gastrointestinal tract, which results in superior distention and mural discrimi-nation of the stomach and duodenum compared with 2% milk, barium suspension, water, or no contrast agent. However, there are no comparable studies on whole milk as a low-attenuation contrast agent for Asians. In this study, we evaluated the efficiency of whole milk as a low-attenuation contrast agent compared with water-soluble contrast medium and water for abdominopelvic CT.
2. Methods
From July 2008 to June 2009, 162 patients referred for oral and intravenous contrast-enhanced abdominopel-vic CT were randomly assigned to receive whole milk (4%), water or water-soluble contrast medium. All pa-tients enrolled in this study provided informed consent. Exclusion criteria included a history of lactose intoler-ance, documented allergy to iodinated contrast material, serum creatinine greater than 1.5 mg/dL, a history of gastric surgery, and individuals undergoing CT primarily for evaluation of liver disorders because the pelvis and
thus the distal small bowel are not routinely imaged. The final number of patients included in the study was 152.
The water-soluble contrast medium used in this study was 30 mL Optiral 350 (Tyco Healthcare, Montreal, Quebec, Canada), which is a type of high-attenuation oral contrast material, to which 970 mL water (3%) was added. The three contrast agents were divided into three doses: 400 mL 90 minutes before scanning, 300 mL 30 minutes before scanning and 300 mL immediately before scanning. All CT scans were performed using a 64-multidetector CT (MDCT) scanner with a 0.35-second rotation time (Volume Computed Tomography Light Speed CT/I; GE Medical Systems, Milwaukee, WI, USA). All examinations were performed using intravenous contrast material that was administrated by means of a power injector (Vistron CT; MEDRAD Inc., Warrendale, PA, USA). All CT images were obtained from the xy-phoid to the pubic symphysis 50 seconds after initia-tion of the intravenous contrast bolus (2 mL/sec; total volume, 100 mL) (Bayer Schering Pharma AG, Berlin, Germany). After reconstruction of the images, two ra-diologists who were blinded to the type of oral con-trast material administered reviewed the images. For bowel wall enhancement, visualization of the antrum, duodenum, jejunum and ileum was evaluated on a yes-or-no basis. For bowel dilation, we graded on a scale of 1–3: 1 = spasm, 2 = mild and 3 = well. In addition, we also provided a questionnaire to every patient. The contents of this questionnaire included the acceptance and the taste of the contrast medium, and whether the patient had difficulty ingesting the entire volume of contrast medium. Side effects of gastrointestinal contrast me-dium were also recorded.
The results are shown as mean ± standard deviation. Statistical analyses of the differences in bowel dilation scores among the three groups were performed by one-way analysis of variance. Differences in bowel dilation scores between whole milk and the other two types of contrast medium were performed by unpaired t test. Data for stomach and bowel enhancement, tolerability and gastrointestinal tract symptoms were analyzed by χ2 test. A p value less than 0.05 was considered statisti-cally significant.
3. Results
The mean ages of the three groups were 49.7 years in the water-soluble contrast medium group, 55.3 years in the water group and 51.6 years in the milk group. There were no significant differences in age among the three groups.
The bowel dilation scores are shown in Table 1. There were no differences in average dilation scores among the three groups for duodenum and jejunum. However, for the antrum, the average dilation score in the milk group was higher than that in the water-soluble contrast
medium group, and there was no difference between water and milk. For the ileum, there were no differences in the average dilation scores in the milk and water-soluble contrast medium groups. In addition, we also observed that milk produced better dilation in the ileum compared with water.
Bowel enhancement visualization is shown in Table 2. We found that enhancement in the water and milk groups was stronger than that in the water-soluble con-trast medium group. This indicates that water and milk produced better wall visualization than high-attenuation contrast medium (Figures 1–3).
Patient tolerability and side effects of the gastroin-testinal tract towards these three contrast materials are
shown in Tables 3 and 4. Patients seemed to tolerate water better than water-soluble contrast medium and milk. In addition, the major symptoms of milk were nausea and flatulence. Because some patients suffered from several symptoms, the sum of the patient numbers in Table 4 is more than 152.
4. Discussion
CT of the gastrointestinal tract is a diagnostic tool for evaluating patients with abdominal diseases. When CT is used for visualization of the small intestinal wall, it re-quires a low-attenuation oral contrast agent.9 Be cause
Table 1 Qualitative analysis of bowel dilation scores*
Water-soluble contrast
Water (n = 51) Whole milk (n = 51) Groups compared p medium (n = 50)
Antrum 2.24 ± 0.87 2.51 ± 0.58 2.69 ± 0.55 Among the three groups† < 0.01
Water vs. whole milk‡ NS
Water-soluble contrast < 0.01
medium vs. whole milk‡
Duodenum 2.0 ± 0.86 2.27 ± 0.78 2.25 ± 0.72 Among the three groups† NS
Water vs. whole milk‡ NS
Water-soluble contrast NS
medium vs. whole milk‡
Jejunum 2.48 ± 0.71 2.35 ± 0.74 2.49 ± 0.61 Among the three groups† NS
Water vs. whole milk‡ NS
Water-soluble contrast NS
medium vs. whole milk‡
Ileum 2.92 ± 0.27 2.41 ± 0.75 2.94 ± 0.24 Among the three groups† < 0.0001
Water vs. whole milk‡ < 0.0001
Water-soluble contrast NS
medium vs. whole milk‡
*Data presented as mean ± standard deviation; †data analyzed by one-way analysis of variance; ‡data analyzed by unpaired t test.
NS = not significant.
Table 2 Analysis of visualization of stomach and bowel enhancement*†
Water-soluble contrast
Water (n = 51) Whole milk (n = 51) p
medium (n = 50) Antrum < 0.05 Yes 0 49 (96.1) 46 (90.2) No 50 (100) 2 (3.9) 5 (9.8) Duodenum < 0.05 Yes 0 41 (80.4) 41 (80.4) No 50 (100) 10 (19.6) 10 (19.6) Jejunum < 0.05 Yes 0 44 (86.3) 45 (88.2) No 50 (100) 7 (13.7) 6 (11.8) Ileum < 0.05 Yes 0 41 (80.4) 46 (90.2) No 50 (100) 10 (19.6) 5 (9.8)
of disadvantages such as poor mural discrimination and interference with two-dimensional and three-dimensional multiplanar reformations of high-attenuation contrast medium, there is a need for low-attenuation oral contrast material.10 A low-attenuation oral contrast agent allows better visualization of the bowel wall and clearer delineation between the bowel cavity and soft tissue.11 In several previous studies, corn oil emulsion, medical-oil based food supplements and water are ef-fective as low-attenuation contrast agents.6,7 However, corn oil has disadvantages such as a high calorie content and gastrointestinal side effects that limit its practical use.5 Thompson et al8 gave 110 consecutive patients whole milk (4% milk), 2% milk, water, barium suspension, or no oral contrast agent before abdominal CT. They reported that 4% milk was superior for distention and mural discrimination in the jejunum and ileum. There was no need to administer a smooth muscle relaxant, such as glucagon, to achieve adequate distention of the
Figure 2 A 33-year-old woman with a pelvic mass who was enrolled in the whole milk study. (A) Transverse enhanced com-puted tomography scan at the level of the lower portion of the liver shows a well-distended antrum with an enhanced mural wall (black arrow), as well as well-enhanced jejunal valvulae conniventes (white arrow), but there was poor mural enhancement of the duodenum (black arrowheads). (B) Transverse enhanced computed tomography scan at the level of the pelvis shows a well-distended ileum with good enhancement of mural walls (black arrows).
A B
Figure 3 A 50-year-old man with a suspicious abdominal mass who was enrolled in the water study. Transverse enhanced computed tomography scan at the level of the inferior portion of the liver shows a well-distended duode-num (white arrow) and proximal ileum (white arrowheads) with good enhancement of mural walls.
A B
Figure 1 A 46-year-old man with right flank pain who was enrolled in the water-soluble contrast medium study. (A) Transverse intravenous enhanced computed tomography scan at the level of the lower portion of the liver shows a well distended antrum (white arrow) with water-soluble contrast medium, but no identifiable mural enhancement of the wall is seen. (B) Transverse intravenous enhanced computed tomography scan at the level of the inferior portion of the liver shows no identifiable water-soluble contrast medium in the lumen of the duodenum (black arrow) causing pseudotumor formation. A well-distended jeju-num with water-soluble contrast (white arrow) and no mural wall enhancement are seen.
upper gastrointestinal tract, which eliminates potential undesirable side effects and additional expense. They concluded that whole milk is an effective low-attenuation oral contrast agent.
In our study, we found that bowel visualization in the water and whole milk group was stronger than that in the oral iodine contrast group. This indicates that water and whole milk produce better wall visualization and mucosal discrimination than high-attenuation contrast medium. Thompson et al8 found that 4% milk is supe-rior for mucosal discrimination of the jejunum and ileum compared with barium suspension. Hebert et al7 used another low-attenuation contrast medium (polyethyl-ene glycol) for abdominopelvic CT and found that poly-ethylene glycol solution has imaging characteristics related to bowel wall visualization. When water is used as an oral contrast agent, it results in excellent luminal and mucosal depiction of the upper gastrointestinal tract.5 Koo et al12 compared the effectiveness of whole milk and VoLumen (a 0.1% barium suspension), a type of low-attenuation contrast medium, using abdominal and pelvic CT. They found no significant differences between whole milk and VoLumen with respect to the degree of mural visualization among all segments, which is consistent with our results. Therefore, whole milk could be an effective material for bowel enhance-ment in abdominal and pelvic MDCT. However, high-attenuation contrast medium is not a very good choice for bowel enhancement in this model.
In our study, we also evaluated the effect of whole milk on the dilation scores of the bowel. We found that
whole milk and water showed better dilation of the an-trum compared with water-soluble contrast medium, and that whole milk showed better dilation of the ileum compared with water. In the duodenum and je-junum, we did not observe any differences between the three contrast materials. Koo et al12 demonstrated that whole milk has excellent antral distention compared with the small bowel. Thompson et al8 showed that whole milk is superior to barium for distention in the ileum. In their study, the loops were easily distinguished as such on the basis of the low-attenuation contents and visualization of the plicae circulares, which obviates a pseudotumor. They demonstrated that whole milk, which contains 4% fat, effectively slows passage through the upper gastrointestinal tract, which results in superior dilation. In our study, we found that the dilation of water was similar to whole milk in the antrum, duodenum and jejunum. However, in the ileum, whole milk showed better dilation compared with water. Most water is rea-bsorbed in the proximal small bowel, and as a result, the distal small bowel is not distended adequately.13 Our results suggest that in upper abdominal MDCT, water and whole milk both show potential as good contrast materials for dilation. However, whole milk should be considered as an alternative to water in cases of dis-ease suspected in the pelvis.
Our results showed that the acceptance of whole milk is not as high as in other studies.12 We believe that this may be because the population in this study was Asian. Whole milk is not a very popular drink in Taiwan. Lactose intolerance often occurs in Taiwanese and,
Table 3 Tolerability results for contrast material*†
Variable rated Water-soluble contrast Water (n = 51) Whole milk (n = 51) p
medium (n = 50)
Taste < 0.05
Intolerable 13 (26.0) 8 (15.7) 12 (23.5)
Unpleasant but tolerable 37 (74.0) 7 (13.7) 29 (56.9)
Pleasant 0 36 (70.6) 10 (19.6)
Difficulty consuming entire volume 27 (54.0) 7 (13.7) 26 (51.0) < 0.05
Aversion to oral contrast material 30 (60.0) 9 (17.6) 24 (47.1) < 0.05
*Data presented as n (%); †data analyzed by χ2 test.
Table 4 Gastrointestinal tract symptoms*†
Symptoms Water-soluble contrast Water (n = 51) Whole milk (n = 51) p
medium (n = 50) Abdominal discomfort 6 (12) 0 2 (3.9) < 0.05 Abdominal cramps 0 0 3 (5.9) < 0.05 Nausea 44 (88) 49 (96.1) 42 (82.4) NS Vomiting 6 (12) 3 (5.9) 6 (11.8) NS Flatulence 0 6 (11.8) 20 (39.2) < 0.05
therefore, milk resulted in major side effects of nausea and flatulence in our study. This could explain why the acceptance of whole milk was different among differ-ent studies.
In conclusion, abdominopelvic MDCT with whole milk provides better bowel dilation and wall visualization compared with high-attenuation contrast medium. Both whole milk and water have potential as good oral con-trast materials for gastrointestinal tract dilation. However, whole milk should be considered as an alternative to water in cases of disease suspected in the pelvic area.
References
1. Hamlin DJ, Burgener FA. Positive and negative contrast agents in CT evaluation of the abdomen and pelvis. J Comput Tomogr 1981;5:82–90.
2. Zwaan M, Gmelin E, Borgis KJ, Rinast E. Non-absorbable fat-dense oral contrast agent for abdominal computed tomography. Eur J
Radiol 1992;14:189–91.
3. Raptopoulos V, Davis MA, Davidoff A, Karellas A, Hays D, D’Orsi CJ, Smith EH. Fat density oral contrast agent for abdominal CT.
Radiology 1987;164:653–6.
4. Horton KM, Fishman EK, Gayler B. The use of iohexol as oral con-trast for computed tomography of the abdomen and pelvis.
J Comput Assist Tomogr 2008;32:207–9.
5. Cohen MD, Schreiner R, Grosfeld J, Weber T, Lemons J, Jansen R. A new look at the neonatal bowel-contrast studies with metriza-mide (Amipaque). J Pediatr Surg 1983;18:442–8.
6. Winter TC, Ager JD, Nghiem HV, Hill RS, Harrison SD, Freeny PC. Upper gastrointestinal tract and abdomen: water as an orally administered contrast agent for helical CT. Radiology 1996;201: 365–70.
7. Hebert JJ, Taylor AJ, Winter TC, Reichelderfer M, Weichert JP. Low-attenuation oral GI contrast agents in abdominal-pelvic computed tomography. Abdom Imaging 2006;31:48–53. 8. Thompson SE, Raptopoulos V, Sheiman R, McNicholas MJ,
Prassopoulos P. Abdominal helical CT: milk as a low-attenuation oral contrast agent. Radiology 1999;211:870–5.
9. Herman S. Computed tomography contrast enhancement princi-ples and the use of high-concentration contrast media. J Comput
Assist Tomogr 2004;28:S7–11.
10. Young BM, Fletcher JG, Booya F, Paulsen S, Fidler J, Johnson CD, Huprich J, et al. Head-to-head comparison of oral contrast agents for cross-sectional enterography: small bowel distention, timing, and side effects. J Comput Assist Tomogr 2008;32:32–8.
11. Malik N, Khandelwal N, Garg K, Suri S. Computed tomography of the abdomen with fat density oral contrast medium. Australas
Radiol 1992;36:31–3.
12. Koo CW, Shah-Patel LR, Baer JW, Frager DH. Cost-effectiveness and patient tolerance of low-attenuation oral contrast material: milk versus VoLumen. AJR Am J Roentgenol 2008;190:1307–13. 13. Erturk SM, Mortele KJ, Oliva MR, Ichikawa T, Silverman SG,
Cantisani V, Pagliara E, et al. Depiction of normal gastrointestinal anatomy with MDCT: comparison of low- and high-attenuation oral contrast media. Eur J Radiol 2008;66:84–7.