AJR 2002; 179:435-436
© American Roentgen Ray Society
Colonic Transit Time and MR Colonography
Céline Savoye-Collet1,
Denis Thoumas1,
Guillaume Savoye2,
Philippe Ducrotté2 and
Jean-Nicolas Dacher1
1 Department of Radiology, Quantif, Rouen University Hospital Charles Nicolle, 1
rue de Germont, F-76031 Rouen, France.
2 Digestive Tract Research Group, Rouen University Hospital Charles Nicolle,
F-76031 Rouen, France.
Received November 7, 2001;
accepted after revision February 11, 2002.
Address correspondence to C. Savoye-Collet.
Introduction
MR colonography has recently been introduced as a possible nonirradiating
method of screening for colorectal cancer. In MR colonography, volumetric
imaging can be combined with sophisticated image processing. This imaging
technique has been shown to be accurate in revealing clinically relevant
colonic polyps larger than 10 mm, with a reported sensitivity of 96% and a
specificity of 93% [1]. The
most common preparation for this technique includes the administration of a
diluted gadolinium enema to distend the colon and to generate a positive
contrast with the colonic wall, so that any polyps present appear as filling
defects [2]. However, patients
find the colonic preparation routine that is required to be unpleasant.
An alternate method has been proposed by Weishaupt et al.
[3]: Labeling stools 48 hr
before colonography via an oral administration of gadolinium (fecal tagging)
renders the signal from the stools equivalent to that of the surrounding enema
while allowing detection of abnormalities. These findings suggest that it may
possible to perform MR colonography in a patient who has not undergone
traditional preparation for imaging of the colon. We used this new method in
five volunteers and correlated it with a radiologic study of colonic transit
time.
Materials and Methods
After receiving approval for our study from the institutional review board,
we obtained written informed consent from five volunteers: four women and one
man (age range, 21-42 years; mean age, 33.8 years). One volunteer had a
history of constipation (one or two bowel movements per week). The others had
no history of digestive disease. All these volunteers underwent a colonic
transit time test 10 days before MR colonography. On each of 6 consecutive
days, we asked the volunteers to ingest 10 identical radiopaque markers. We
then obtained a single anteroposterior supine MR image of the abdomen of the
volunteers. The global colonic transit time (in hours) was deduced from
multiplying the number of remaining markers by 2.4 hr
[4]. During the 2 days before
undergoing MR colonography, each patient ate a low-fiber diet providing the
normal number of calories (three meals a day). Volunteers drank 10 mL of 0.5
mol/L gadoterate meglumine solution (Dotarem; Guerbet, Villepinte, France)
mixed with water after each of the six consecutive meals with the exception of
the two meals preceding MR colonography. No bowel cleansing was used.
MR imaging was performed on a 1-T system (Gyroscan NT 1.0; Philips Medical
Systems, Eindhoven, The Netherlands). The process of filling the colon with
2000 mL of water mixed with 20 mL of 0.5 mol/L gadoterate meglumine solution
was monitored using a two-dimensional gradient-echo MR sequence. Just before
filling the bowel, we gave volunteers 15 mg of tiemonium methylsulfate
(Visceralgine; Laboratoires CERM, Riom, France) IV to optimize colonic
distention and minimize peristaltic artifacts. We then used a
three-dimensional gradient-echo MR sequence (TR/TE, 6/1.7; flip angle,
30°; matrix, 512 x 164; field of view, 410 mm; slice thickness, 2
mm; and single breath-hold phase, 26 sec) to image the colon.
For virtual colonoscopy reconstruction, the data were downloaded to a
workstation (Virtuoso; Siemens, Erlangen, Germany). We performed an
intraluminal navigation using perspective volume-rendering techniques. Image
analysis was based on both native coronal three-dimensional images of the
colon and virtual colonoscopic images. The location and abundance of
endoluminal untagged stools (tagged ones were not visible even if present)
were recorded. Each segment of the colon (cecum and right colon; transverse
colon; left colon and sigmoid colon; and rectum) was given a subjectively
determined score indicating the percentage of lumen containing residual
untagged stools visualized (minor, < 10% of lumen with residual stools;
moderate, 10-50%; and major, > 50%). The colonic transit time was compared
with the quality of the endoluminal analysis.
Results
In the colon of one volunteer (colonic transit time, 38 hr 24 min), only a
minor percentage of lumen with untagged stools remained in the cecum. A minor
percentage of lumen with residual stools was identified in all four parts of
the colon of the second volunteer (colonic transit time, 44 hr 42 min). Except
for a moderate stagnation in the transverse colon and a minor percentage of
lumen with residual stools in the cecum, a third volunteer (colonic transit
time, 48 hr) had an apparently clean colon. Another volunteer (colonic transit
time, 60 hr) had a minor to moderate percentage of lumen with residual
untagged stools throughout the colon. The final volunteer who had a history of
constipation (colonic transit time, 139 hr) had major stagnation in all parts
of the colonic lumen, which made analysis impossible. We believe that a
prolonged colonic transit time in a patient can be used to predict the failure
of the fecal tagging technique in that individual. That was the case with our
last two volunteers, both of whom had colonic transit times exceeding 60 hr
(Fig.
1A,1B).
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Fig. 1A. —MR colonography of 41-year-old healthy woman with colonic
transit time of 60 hr. Coronal 2-mm-thick gradient-echo MR image obtained
through transverse colon shows residual stools appearing as dark filling
defects.
|
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View larger version (123K):
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Fig. 1B. —MR colonography of 41-year-old healthy woman with colonic
transit time of 60 hr. Virtual endoscopic MR image of transverse colon reveals
residual stools (arrow) in lumen in dependent position and provides
intraluminal perspective and visualization of haustra.
|
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Discussion
Structural examinations of the colon require that patients perform
uncomfortable colonic purging, which contributes to the reluctance of patients
to undergo such procedures. Oral administration of positive tagging is an
elegant solution that eliminates the need for colonic cleansing. However,
adequate stool labeling is mandatory to detect endoluminal abnormalities, such
as a polyp or a tumor. An oral preparation administered 48 hr before MR
colonography has previously been recommended
[3]. This 48-hr-delay regimen
seems to have been adopted for use in patients with normal colonic transit.
However, because we found that stool tagging failed in volunteers with
prolonged colonic transit times, we suggest that a colonic transit time test
be performed before a patient undergoes MR colonography. This preliminary step
ensures that fecal tagging can be closely adapted to suit each patient's
individual colonic transit time.
In this study, we used gadolinium tagging, which is rather expensive.
Colonic transit time testing could be performed with any other kind of fecal
tagging, such as using barium sulfate
[5]. This procedure could be
used for CT examination, because stool labeling has also been suggested for CT
colonography [6]. The exact
timing to be used in CT requires further study. Our study shows that measuring
colonic transit time using fecal tagging before MR colonography eliminates the
need for bowel preparation and provides adequate labeling.
Acknowledgments
We thank Guerbet France (Villepinte, France) and the Centre de Recherche
Clinique (Rouen University Hospital) for providing technical assistance.
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Introduction
Materials and Methods
