AJR 2003; 180:1332-1334
© American Roentgen Ray Society
Carpet Lesion on CT Colonography: A Potential Pitfall
Greg M. Galdino1 and
Judy Yee2
1 Department of Radiology, University of California at San Francisco, 563 20th
Ave., San Francisco, CA 94121
2 Department of Radiology, University of California at San Francisco, San
Francisco Veterans Administration, 4150 Clement St., San Francisco, CA
94121
Received June 21, 2002;
accepted after revision August 27, 2002.
Address correspondence to G. M. Galdino.
Introduction
Carpet lesions of the colon were first described using double-contrast
barium enema by Rubesin et al.
[1] and defined as flat,
lobulated lesions causing an alteration in surface texture. They often involve
a large surface area of the colon with little or no protrusion into the lumen.
These lesions have been reported to be largely benign; however, a greater
incidence of malignant degeneration occurs over time than initially thought
[2]. To our knowledge, the
incidence of malignant degeneration or the prevalence of these lesions has not
been reported, and the appearance of these lesions and have not been described
using CT colonography. We present a case illustrating the potential pitfall of
missing this type of lesion on CT colonography.
Case Report
An 81-year-old man with a history of diverticulosis and colonic polyps
presented for elective outpatient colonoscopy and follow-up screening. He
denied any gastrointestinal symptoms but was noted to be slightly anemic (13.9
g/dL). He did not have a family history of colon cancer and had not undergone
colorectal cancer screening for 10 years. He was enrolled in an internal
review board–approved study, and informed consent was obtained.
Double-contrast barium enema was initially performed. CT colonography and
standard colonoscopy were performed on the same day, 7 days after the barium
enema examination. Two radiologists who were experienced in gastrointestinal
radiology and CT colonography interpreted the barium enema and the CT
examinations. Both radiologists were unaware of the patient's history and the
results of all colon tests.
On the double-contrast barium enema examination, the radiologist noted that
the study was limited secondary to retained fecal material and a redundant
colon but reported no abnormalities. The presence of small polyps, however,
could not be excluded.
CT colonography was performed immediately before colonoscopy. The
radiologists scanned the patient in the supine and prone positions using a
multidetector CT scanner (LightSpeed; General Electric Medical Systems,
Milwaukee, WI) with a protocol consisting of a 3-mm slice thickness, 1.5-mm
reconstructions, 150 kVP, and 120 mA. The images were interpreted using a
Vitrea 2 workstation (Vital Images, Plymouth, MN) by one radiologist with
extensive CT colonography experience using primary two-dimensional
interpretation with three-dimensional problem solving. Colonic distention was
noted to be excellent in all segments except the sigmoid colon. However, a
large amount of residual fluid was noted in the ascending, descending, and
sigmoid colon on the supine scan, and an extensive amount of fluid was noted
in the cecum on the prone scan.
Subsequent colonoscopy revealed a flat, 6.0 x 3.5 cm, nonbleeding
mass in the cecum (Fig. 1A).
The mass had a lobulated appearance and involved half of the cecal surface.
Multiple biopsies were performed and revealed as fragments of tubular adenoma.
The patient had refused surgical intervention.
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Fig. 1A. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Fiberoptic colonoscopy image
shows extreme nodularity of surface of lesion and similar appearance of tissue
of surrounding colonic mucosa in cecum. Lesion appears to involve surface of
entire haustral fold. Lesion was initially diagnosed on fiberoptic
colonoscopy.
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A retrospective examination of the double-contrast barium enema revealed a
large area of mucosal irregularity involving the cecum
(Fig. 1B). Reexamination of the
CT colonography showed irregular, nodular, and fold thickening in the cecum
seen only on the supine scan (Fig.
1C). The three-dimensional endoluminal image similarly showed a
large area of irregular nodularity (Fig.
1D). Most of this lesion was obscured by residual fluid on the
prone scan (Fig. 1E). The
irregularly thickened fold could be seen on the coronal reformatted image and
involved half of the haustral fold (Fig.
1F).
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Fig. 1B. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Image from double-contrast
barium enema study shows lesion (arrows) en face and reveals
irregular mucosal contour involving half of cecal haustral fold compared with
smooth contour of remaining half of fold. This lesion was missed on initial
interpretation.
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Fig. 1C. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Two-dimensional axial CT
colonography image with patient in supine position shows irregular, nodular
appearance of lesion and thickened appearance of haustral fold compared with
other folds present on image. Lesion spans entire haustral fold
(arrows) on this image. Carpet lesion was initially interpreted as
adherent stool on haustral fold.
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Fig. 1D. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Three-dimensional
endoluminal CT colonography image shows nodular, irregular surface texture of
lesion on fold as well as normal smooth surface of fold.
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Fig. 1E. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Two-dimensional axial CT
colonography image with patient in prone position shows lesion
(arrow) is almost completely obscured by residual fluid.
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Fig. 1F. —81-year-old man with history of prostate cancer, diverticulosis, and
colonic polyps presented for follow-up screening. Two-dimensional coronal CT
colonography image with patient in supine position shows carpet lesion
(arrows) and adjacent normal mucosa on same fold.
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Discussion
Carpet lesions have been recognized as a separate entity from flat
adenomas, flat depressed adenomas, and plaquelike carcinomas. Carpet lesions
have been grouped with villous tumors, given their propensity to contain
villous components. The prevalence of carpet lesions is uncertain and, to our
knowledge, has not been reported; however, Glick et al.
[2] stated that in their
experience, carpet lesions are fairly commonly occurring lesions, especially
in high-risk patients.
Rubesin et al. [1] reported
that in their series of 14 lesions, all lesions showed varying amounts of a
villous growth pattern at histology, with severe dysplasia present in only one
lesion. One of the 14 lesions contained invasive carcinoma arising in a
tubular adenoma, suggesting that these lesions represented a benign pathology
despite their large size at diagnosis (11/14 lesions were > 2 cm). All
lesions were resected. However, Glick et al.
[2] reported that, in their
series of 18 large colonic lesions missed by endoscopy and found on
double-contrast barium enema, six of 11 tumors that were resected showed
malignant foci. Two additional unresected lesions without initial histology
progressed to advanced carcinomas. Thus, eight of 18 lesions were either
malignant or premalignant. The size of lesions in the series by Glick et al.
ranged from 2 to 8 cm, with an average size of 4.4 cm. Twelve of the lesions
exhibited the morphology of carpet lesions, whereas two exhibited mixed
components of carpet and polypoid lesions. The remaining four lesions were
described as flat sessile polyps with a nonuniform lobular contour and a width
at least three times the height.
Carpet lesions occur predominantly in the cecum, ascending colon, and
rectum for reasons that are not well understood
[1,
3]. Morphologically, they
appear as flat, nodular, or lobulated lesions with little or no protrusion
into the colonic lumen. Carpet lesions are larger at diagnosis and can involve
a significant portion of the colonic surface area. The lesions can also be
seemingly indistinguishable from the normal surrounding colonic mucosa on
colonoscopy [2].
Histologically, these lesions may contain only tubular adenomatous components;
however, most of these lesions contain at least some villous change. Given the
large size of carpet lesions, it is somewhat difficult to completely examine
the entire lesion for malignant foci, particularly if biopsies are performed
only endoscopically. Although their malignant degenerative potential is
unclear, in a small series of random cases, these lesions tended to degenerate
to malignancy over time, especially with increasing size
[2]. Thus, surgical resection
is currently the recommended treatment for all carpet lesions
[2].
In our case report, the lesion was discovered on colonoscopy and missed on
both double-contrast barium enema and CT colonography, despite the fact that
the lesion was visible on both studies retrospectively. On double-contrast
barium enema, carpet lesions are best seen en face and appear as a
fine nodular or reticular pattern of plaques or nodules, usually with sharply
demarcated borders [3]. Carpet
lesions can also been seen as contour abnormalities on the wall of the
colon.
To our knowledge, no reports of the appearance of carpet lesions on CT
colonography have been documented in the literature. The carpet lesion in our
patient appeared as a large area of nodular irregular fold thickening with a
homogenous soft-tissue density throughout. Multiplanar reformatted images were
helpful in delineating the lesion from the normal-appearing haustral fold.
A good preparation of the colon is probably the most important factor
enabling the delineation of a carpet lesion from other entities on CT
colonography. Residual stool can resemble a carpet lesion, particularly if the
stool adheres to a haustral fold (Fig.
2A,
2B), and often appears more
heterogenous but can have a homogenous appearance. Mobility on dual-position
scanning and the identification of residual stool in adjacent segments can
help differentiate stool from a carpet lesion. A thickened or bulbous fold can
resemble a carpet lesion but is typically smooth in contour on both axial and
reformatted images.
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Fig. 2A. —50-year-old man with incomplete cleansing and large amount of solid,
residual stool. Two-dimensional axial CT colonography image with patient in
supine position shows that large amount of solid residual stool adherent to
haustral fold (arrows) can mimic appearance of carpet lesion on CT
colonography. Note similar irregular, nodular surface making fold appear
thickened.
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Fig. 2B. —50-year-old man with incomplete cleansing and large amount of solid,
residual stool. Three-dimensional endoluminal CT colonography image shows
similar surface texture to carpet lesion.
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Several other clinical entities can mimic a carpet lesion both on
double-contrast barium enema and potentially on CT colonography, although
these entities have not appeared in the literature for CT colonography.
Endometriosis, rectal varices, nonspecific proctitis, and follicular proctitis
can all cause contour abnormalities, nodular patterns, and a thickened colonic
wall. Submucosal spread of a tumor or a prior biopsy site may create a
morphologic appearance similar to that of a carpet lesion. Familial polyposis
syndrome can mimic a carpet lesion but tends to involve a substantially
greater portion of the colonic surface. Lastly, a colonic urticarial pattern,
with its typical reticular mosaic pattern of submucosal edema, can be seen
with colonic ileus, Yersinia enterocolitica, herpetic infection,
urticaria, colonic volvulus, obstructing carcinoma, ischemia, and Crohn's
disease and can resemble the appearance of a carpet lesion on double-contrast
barium enema and possibly on CT colonography
[1].
In conclusion, carpet lesions of the colon present a potential pitfall for
CT colonography. Although the prevalence and malignant potential of these
lesions are not fully known, surgical intervention is recommended as the
treatment. These lesions can become malignant if left undiagnosed. A clean
colon that is adequately distended and dual-position scanning are essential
for the depiction of these lesions on CT colonography.
References
- Rubesin SE, Saul SH, Laufer I, Levine MS. Carpet lesions of the
colon. RadioGraphics 1985;5
: 537–552[Abstract]
- Glick SN, Teplick SK, Balfe DM, et al. Large colonic neoplasms
missed by endoscopy. AJR
1989;152:513
–517[Abstract/Free Full Text]
- Levine MS, Rubesin SE, Laufer I, Herlinger H. Diagnosis of
colorectal neoplasms at double-contrast barium enema examination.
Radiology
2000;216:8
–11[Free Full Text]
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Introduction
Case Report
