Magnetic resonance colonography for colorectal cancer screening

Colorectal cancer screening has vast potential. Beyond considerations of cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further enhance patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. This article will describe the techniques underlying MR colonography and early clinical experience with fecal tagging techniques.     

Dark lumen MR colonography based on fecal tagging for detection of colorectal masses: accuracy and patient acceptance

Background Magnetic resonance colonography (MRC) with fecal tagging has recently been investigated in clinical studies for the detection of polyps. We assessed fecal tagging MRC in a field trial. Methods Forty-two patients in a private gastroenterologic practice underwent MRC with barium-based fecal tagging (150 mL of 100% barium at each of 6 main meals before MRC) and conventional colonoscopy. Diagnostic accuracy of MRC and patient acceptance were assessed and compared with the respective results of conventional colonoscopy. Results Eighteen percent of all MRC examinations showed a remaining high stool signal in the colon that impeded a reliable inclusion or exclusion of polyps. On a lesion-by-lesion basis, sensitivities for polyp detection were 100% for polyps larger than 2 cm (n = 1), 40% for polyps between 10 and 19 mm, 16.7% for polyps between 6 and 9 mm, and 9.1% for polyps smaller than 6 mm. The main reason for the low acceptance of MRC was the barium preparation, which was rated worse than the bowel cleaning procedure with conventional colonoscopy. Conclusion MRC with fecal tagging must be further optimized. The large amount of barium resulted in poor patient acceptance, and barium according to this protocol did not provide sufficient stool darkening. Other strategies, such as increasing the hydration of stool, must be developed.     

Diagnostic accuracy of MR colonography with fecal tagging

Background  MR colonography (MRC) is a non-invasive method of examining the colon, but it is still only used in a few specialized centers on a daily basis. The purpose of this study was to evaluate the performance of MRC with improved fecal tagging vs. conventional colonoscopy (CC). Methods  Between March 2006 and February 2007, consecutive patients who received first-time referrals to CC were asked to participate in the study. Two days prior to MRC, a new contrast mixture (barium/ferumoxsil) was ingested together with four meals each day. Standard bowel cleansing was performed before CC. MRC was evaluated by two blinded observers. MRC results were compared with CC. Results  A total of 56 patients were included. The per-polyp sensitivity was 85.7% for polyps 6–10 mm and 81.3% for polyps >10 mm. The per-patient sensitivity/specificity was 100%/80% for polyps >6 mm and 100%/91.4% for polyps >10 mm. Conclusion  MRC showed acceptable per-patient sensitivities, but the per-polyp sensitivities are still compromised by the fecal tagging. MRC may be implemented, but at the present time MRC with fecal tagging is not ready for widespread use, although it remains a very promising diagnostic tool.     

Implementation of MR colonography

Background MR colonography (MRC) is a promising method of examining the colon, but is limited to a few specialist centres. The purpose of this article was to describe the implementation of MRC with fecal tagging. Materials and methods Patients referred for conventional colonoscopy (CC) were offered MRC with fecal tagging before CC. Two days before MRC patients ingested an oral contrast agent. Before and after MRC and CC a number of questions were addressed. MR images were rated by a blinded investigator. Results In 6 months, 30 consecutive patients were included. The median time in the MR suite was 44 min, 23 min for the MRC examination and 9 min for the evaluation. The median time for CC was 32 min. Sixty-six percent of the patients preferred MRC as the future method of examination, 10% preferred CC, 21% had no preferences. Of the oral contrast agents, barium sulphate with ferumoxsil was significantly better than barium sulphate alone. Conclusion The majority of the patients found MRC less unpleasant than CC and a majority would prefer MRC over CC as a future colon examination. MRC also appears to be less time consuming to the patients and medical personnel than CC with post-procedural monitoring.     

Interval between cleansing enema and barium examination of the colon

A prospective, randomized, blinded study was conducted to determine the optimal length of time a patient should wait after evacuating a cleansing enema prior to undergoing barium enema. Evaluation of overhead films, graded for the amount of retained fluid and fecal material, detected no significant improvement in colon examinations that were delayed longer than 30 min. Patient acceptance and scheduling can be improved by eliminating unnecessary waiting.     

Dark-lumen MR colonography

Magnetic resonance colonography (MRC) has been shown to be an appropriate diagnostic tool for the detection of colorectal pathologies. Recently, dark-lumen MRC has been introduced. This technique is based on the acquisition of a T1-weighted sequence after the administration of water enema and the intravenous administration of paramagnetic contrast. This report describes the underlying techniques of dark-lumen MRC concerning data acquisition and image interpretation. Furthermore, it points out the advantages of this approach as compared with conventional endoscopy or other MR methods. Possible improvements in the future such as the implementation of fecal tagging strategies to avoid bowel cleansing are discussed.     

Magnetic resonance colonography with fecal tagging: an innovative approach without bowel cleansing

To date, virtual colonography mandates bowel cleansing in a manner similar to colonoscopy. Because more than half of patients undergoing bowel preparation complain about negative side effects, patient acceptance is negatively impacted. To assure high patient acceptance of MR colonography, bowel cleansing needs to be eliminated. This can be accomplished by fecal tagging, a concept based on altering the signal intensity of stool by adding contrast-modifying substances to regular meals. This article describes different fecal tagging approaches and points out both advantages and limitations of these strategies.     

The role of barium enema in detecting colorectal disease. A radiologist's perspective.

The single-contrast barium enema examination remains useful for patients with acute diseases such as bowel obstruction, diverticulitis, appendicitis, and fistulas. It is also the procedure of choice for those patients who are too elderly, debilitated, or ill to cooperate with the maneuvers necessary for a double-contrast examination. The double-contrast technique is more sensitive than the single-contrast technique for detection of polyps, early inflammatory bowel disease, and lesions of the rectum. In the older population, there has been an increase in the incidence of colonic polyps and carcinomas in the right side of the colon. This emphasizes the need to examine the entire colon in these patients. The double-contrast barium enema is a safe, accurate, and cost-effective tool for accomplishing this. It is also recommended as the initial procedure in the examination of patients with positive results on fecal occult blood testing.     

Changing concepts of colonic polyps: clinical and radiographic implications

The relationship of colonic polyps to carcinoma of the colon provides a basis for their importance. Recent advances in the detection of colonic polyps, including double contrast barium examination and colonoscopy, have provided a method for more extensive study of colonic polyps. Studies using these newer techniques indicate that many traditional concepts of colonic polyps were inaccurate. The relationships of polyp size to histology, polyp location to age, and the phenomenon of colon polyp clustering are important to both the immediate treatment of the polyp and to the long-term follow-up of the patient. The use of hemoccult stool screening as a technique for screening for colonic pathology is also of significance to the radiologist. The changing relationships of various parameters of colon polyps bring into question the utility of many of the currently recommended screening procedures for colon pathology. Undoubtedly, this will impact on the practice of radiology.     

CT colonography: examination prerequisites

CT colonography is likely to play an important role in colorectal cancer screening. The ability of this new technique to detect colorectal polyps and cancer is predicated on an optimally cleansed and distended colon. Whereas the most common reported colonic cleansing regimen employed for CT colonography is polyethylene glycol lavage solution, saline cathartics such as sodium phosphate and magnesium citrate offer the advantage of a drier cleansed colon. Positive labeling of residual stool and fluid combined with electronic substraction of tagged material is under investigation. This new technique would eliminate purgative bowel cleansing and increase patient acceptance of CT colonography. Colonic distention is easily and reliably achieved with atmospheric air, although carbon dioxide is being evaluated as a more comfortable alternative. The use of antispasmodics for CT colonography is controversial. Glucagon is no longer used at centers where a clear benefit has not been found. Intravenous contrast may be useful in a specific subset of patients undergoing CT colonography, although it is doubtful that it will be used routinely for CT colonography.     

Water as contrast medium for computed tomography study of colonic wall lesions

A tap water enema combined with intravenous iodine contrast medium was used for computed tomographic (CT) study of the entire clean colon in 35 patients. Thirty of them showed a high suspicion of rectal, colon, or cecal pathology at either clinical examination, barium enema study, or endoscopy. The remaining five patients were examined for suspected local recurrence of carcinoma. This CT technique detected the wall abnormality in all but one case with two small adenomatous polyps. This procedure, which is simple, inexpensive, and has a good acceptance and tolerance, can accurately detect mural wall abnormalities.     

Predictive value of a diagnosis of colonic polyp on the double-contrast barium enema

The positive predictive value of a diagnosis of colonic polyp on the double-contrast barium enema was determined by analyzing 160 polypoid lesions reported in 105 patients. Of the 160 polyps, 139 were confirmed by endoscopy, surgery, or repeat barium enema for a positive predictive value of 87%. Twenty-one lesions were not confirmed despite repeat endoscopy, repeat barium enema, review of the original study, or surgery, giving a false positive rate of 13%. The individual false positive error rates of 5 radiologists ranged from 8% to 26%. False positive errors were due to stool, diverticula, air bubbles, misinterpretation of the ileocecal valve, and haustration. Many of the false positive errors appeared to have been avoidable if the original examination had been more meticulously interpreted.     

Randomized single-blind clinical trial of a rapid colonic lavage solution (Golytely) vs. standard preparation for barium enema and colonoscopy

A randomized single-blind clinical trial was conducted to compare the effectiveness and acceptance by patients of a new oral balanced lavage solution with those of a standard preparation for cleansing the colon for barium enema (50 patients) and colonoscopy (20 patients). The quality of preparation was comparable for the 2 preparations. For colonoscopy, Golytely preparation resulted in slightly better results than standard preparation. Patient acceptance was comparable for the 2 preparations. We conclude that Golytely can be used as an alternative to standard preparation for barium enema. For colonoscopy, it is slightly superior to standard preparation.Presented at the Society for Gastrointestinal Radiology Meeting, Bermuda, October 1983Braintree Laboratories, Braintree, MA. Other PEG lavage solutions of similar content are also available     

Radiology in the current assessment of ulcerative colitis

Plain abdominal radiography in acute ulcerative colitis is essential to detect acute colonic complications, such as acute dilatation and free perforation. Sealed perforations may not be detected. Useful information can be gained as to the extent and severity of the mucosal lesions, but can be unreliable so that a contrast examination is required. The double contrast barium enema is more accurate than the single contrast study in revealing the early mucosal lesions of colitis. It is the examination of choice to show the extent and severity of disease, and is of considerable value in the differential diagnosis of colitis. In active colitis, the unprepared double contrast barium enema is recommended. The success of the examination relies on the absence of fecal residue adjacent to an active mucosa. The technique, uses, and limitations of this type of examination are described.In the long-term management of colitis, the role of radiology is to show the presence of extensive disease, which indicates an increased risk of malignancy. Lesions such as strictures or polyps may be found and are more likely to be benign than malignant, but confirmation often requires endoscopic biopsy. In the search for malignancy regular barium enema examination is not recommended, as this can only reveal an overt tumor, whereas premalignancy can be detected histologically from an endoscopic biopsy.     

预防性末端回肠双腔造口患者应用顺行结肠灌洗的效果

目的评价预防性末端回肠双腔造口患者应用顺行结肠灌洗法后的肠道准备效率及患者舒适度。方法将80例低位直肠癌经腹前切除＋末端回肠双腔造口术的病例随机分成顺行灌洗组（40例）和传统灌肠组（40例）,比较两种方法灌肠后,患者的主观感受、灌肠时间和肠道清洁度。结果顺行灌洗组患者的主观感受好于传统灌肠组,且该组的灌肠时间少于传统灌肠组,差异有统计学意义（P〈0.05）;顺行灌洗组患者的肠道清洁度明显优于传统灌洗组,差异有统计学意义（P〈0.05）。结论自造口顺行结肠灌洗法是预防性双腔造口患者肠道准备的理想方式。     

Spontaneous dissection of air into the transverse mesocolon during double-contrast barium enema

Intramural perforation of the colon proximal to the rectosigmoid is a rare complication of the barium enema examination. We present a case in which air and barium entered the wall of the transverse colon, and then dissected through the transverse mesocolon during double-contrast barium enema in an asymptomatic patient with no known underlying colonic disease.     

Does the addition of an oral barium tracer improve the ability of the preliminary abdominal radiograph to assess efficacy of colonic cleansing? A prospective randomized controlled evaluation

BACKGROUND: We investigated whether the ability of preliminary abdominal radiography to assess the adequacy of colonic preparation is improved by the addition of an oral barium tracer to the laxative preparation and the optimal dosage of this tracer. METHODS: A single-blind, randomized controlled evaluation of four parallel groups of adult patients was performed. All patients were scheduled to a receive a double-contrast barium enema at a tertiary care hospital or an outpatient clinic. RESULTS: One hundred nineteen patients were randomized into four groups. There was no significant difference in the ability of plain abdominal radiography to predict the adequacy of the bowel preparation between the control group and the groups given 60 or 150 g of barium tracer. There was an improved correlation between findings of preliminary abdominal radiography and the adequacy of colon preparation between the control group and the group given 240 g of oral barium tracer (67% vs. 90%). CONCLUSION: The use of a large amount (240 g) of oral barium tracer with the colonic preparation improves the ability of preliminary abdominal radiography to predict the adequacy of colonic cleansing.     

Impact of the barium enema on patient management

The medical records of 214 consecutive inpatients who had a barium enema examination were reviewed, and the clinical indications, efficacy of the barium enema, and patient outcome were correlated to determine the impact of the barium enema on patient management. The most frequent indications were rectal bleeding (33%), abdominal pain (31%), anemia (17%), weight loss (12%), and previous lesions needing reevaluation (12%). Diverticular disease (30%), colonic polyps (10%), and primary or secondary malignancies (12%) were the most common abnormalities detected radiographically. The sensitivity of the barium enema for colonic neoplasms was 89%, with only 1 small cecal polyp being undetected. The effects of barium enema on patient management were serious pathology excluded (64%), diagnosis made that changed therapy (24%), existing therapy continued (10%), and a further study ordered (2%). No serious or life-threatening lesion was missed by barium enema.     

Pneumoperitoneum occurring during double-contrast enema

A case of pneumoperitoneum occurring during double-contrast barium enema is described. Cases reported to date indicate that colonic rupture during a double-contrast enema is likely to result in exit of air rather than barium from the colon. The diagnostic implications of this observation are considered. The potentially high pressure generated by bulb-type inflators is discussed, and caution is advised against overdistending the colon during double-contrast enemas.     

Colon cleansing regimens

The purgative effect of bisacodyl, anthraquinone glycosides (Cascara), and sodium picosulfate, alone or in combination with a saline purge and a tap water enema, was studied in 1200 patients. The cleansing effect was scored with regard to retained fecal residue evident on double-contrast studies of the colon.The combination of a contact laxative and a saline purge produced good cleansing effect in 52%–80% of the patients. With an additional tap water enema given 1 hour before the colon examination, however, 96% of the colons were clean.The taste and the effects of the cleansing systems were tolerated favorably by more than 90% of the patients. However, 17% reported restriction in work capacity on the day of bowel cleansing.