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1 Department of Radiology, Sahlgrenska University Hospital, The Sahlgrenska
Academy at Göteborg University, Göteborg 413 45, Sweden.
2 Department of Medicine, Sahlgrenska University Hospital, The Sahlgrenska
Academy at Göteborg University, Göteborg 413 45, Sweden.
3 Department of Medicine, Borås Hospital, Borås 501 82,
Sweden.
Received December 20, 2002;
accepted after revision September 3, 2003.
Address correspondence to M. Hellström
(mikael.hellstrom{at}xray.gu.se).
Abstract
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SUBJECTS AND METHODS. One hundred eleven symptomatic patients referred for colonoscopy underwent CT colonography before colonoscopy. Helical CT from the diaphragm to the symphysis was performed with the patient in the supine and prone positions after rectal air insufflation. Image interpretation was done on a digital workstation. Extracolonic findings were classified as minor, moderate, or major according to potential clinical importance. Patient records, with a follow-up time of about 3 years, were reviewed to determine final diagnoses.
RESULTS. Twenty-six (23%) of the patients had CT findings of major importance such as lymphadenopathy (n = 7), aortic aneurysm (n = 6), suspected solid hepatic masses (n = 5), and suspected solid renal masses (n = 4). Fifty-eight patients (52%) had findings of moderate importance such as gallstones (n = 16), indeterminate renal masses (n = 9), adrenal masses with benign appearance (n = 8), and hiatal hernia (n = 7). Forty-six patients (41%) had no or only minor findings, such as renal cysts (n = 34), renal calcifications (n = 19), and hepatic cysts (n = 14). Review of patient records showed that CT colonography contributed to the detection of major, previously unknown extracolonic disorders in 14 (13%) of the 111 patients.
CONCLUSION. Potentially important extracolonic findings were revealed in 23% of the patients, leading to additional diagnostic or therapeutic considerations. Some of these findings were clinically important, whereas others were previously known or led to unnecessary workup. This finding must be taken into account when CT colonography is considered for routine diagnostic workup or screening.
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The study group consisted of 111 individuals; age and sex distribution are shown in Table 1. In 48 patients, the indication for the examination was anemia, rectal bleeding, or positive findings on a fecal occult blood test, whereas five patients had suspected malignancy with no colonic symptoms, 11 had previous findings at barium enema, 16 had diarrhea, 16 had abdominal pain or diverticulitis, and 15 were referred for colorectal cancer surveillance after removal of colorectal adenomatous polyps (nine patients) or because of inflammatory bowel disease (six patients).
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Technique
All patients underwent CT colonography immediately before conventional
colonoscopy [7]. Standard bowel
preparation for colonoscopy was used. CT colonography was performed during
suspended respiration with helical CT of the abdomen and pelvis after rectal
air insufflation of the colon. No IV or oral contrast medium was given. To
relieve bowel spasm, reduce bowel motion, and optimize distention,
butylscopolamine (Buscopan, Boehringer Ingelheim, Stockholm, Sweden; 40 mg,
n = 87) or glucagon (Glucagon, Novo Nordisk Pharma, Malmö,
Sweden; 1 mg, n = 24) was administered IV. Helical scanning from the
diaphragm to the symphysis pubis was performed with the patient in the supine
and prone positions with 5-mm slice thickness, a pitch of 1.25, 125 mAs, and
110 kVp (PQ 5000 CT scanner, Picker International, Cleveland, OH). Image
reconstruction was performed at 2-mm intervals
(Table 1). All analyses were
done on a digital CT workstation (Voxel Q, Picker International) equipped with
software for virtual endoscopy (Voyager; Picker International) and using
variable window settings and cine mode image presentation when needed. The CT
images were jointly scrutinized by an experienced abdominal radiologist and a
radiology resident specially trained in CT colonography and abdominal
radiology, using a detailed study protocol including location, size, and
attenuation characteristics of extracolonic findings. The image data set
obtained in the supine position was used for analysis in each case, and the
prone data set was used to confirm abnormal findings or to resolve diagnostic
problems encountered on the supine data set. Patient history and the results
of colonoscopy, radiologic studies, and other tests were not known to the
observers.
Definitions
Extracolonic CT findings were classified as minor, moderate, or major.
Findings considered to be of no or little clinical importance were classified
as minor; findings of potential moderate clinical importance (e.g., needing
verification of patient history or clinical, radiologic, or other follow-up)
were classified as moderate; findings of definite or potential major clinical
importance were classified as major.
Kidneys and liver.—A renal [8] or hepatic cyst was defined as a sharply marginated, rounded or oval, thin-walled, homogenous mass with a density of 20 H or less, and it was considered to be of minor importance. Solid-appearing masses (> 20 H) measuring more than 10 mm were considered to be of major importance. Cyst-like masses were considered to be of moderate importance if the density was more than 20 H but the size was 10 mm or less, or if there was wall thickening, irregular outline, or irregular texture.
In the kidney, a cyst-like, sharply marginated, rounded, clearly hyperdense mass (suspected hemorrhagic cysts) and a mass with fatty (negative attenuation value) content (angiomyolipoma) were considered to be of moderate importance.
Calcifications in the kidney and collecting system were registered, but because of the lack of IV contrast administration, distinction between renal parenchymal, papillary, vascular, and collecting system calcifications could not always be made. A calcification was considered to be of minor importance unless it was 5 mm or larger or was clearly suspected of being located in the collecting system (suspected urinary stone). Suspected urinary stones were considered to be of moderate importance unless combined with urinary tract dilatation (major importance).
In the liver, steatosis (minor importance) was defined as a hepatic density less than that of the normal-appearing spleen at visual inspection, confirmed by CT hepatic density measurements at least 2.3 H lower than those of the spleen [9].
Spleen.—Because of the normal variation in shape of the spleen, splenomegaly was subjectively evaluated. Splenomegaly was defined as apparent enlargement or bulkiness with a long axis exceeding 13 cm [10]. Splenomegaly was considered to be of moderate importance, unless it was gross (major importance). Splenic calcifications were considered to be of minor importance.
Adrenal glands.—An adrenal mass was defined as generalized enlargement (hyperplasia) or any focal mass of the adrenal. Hyperplasia and benign-appearing masses were considered to be of moderate importance. Benign appearance was defined as a mass not larger than 30 mm (largest diameter) with a homogenous density of 10 H or less [11]. An indeterminate adrenal mass was defined as a mass with a density of 11 H or more or as a mass of irregular density or a size of more than 30 mm regardless of density. Such lesions were considered to be of major importance.
Uterus.—Because of the interindividual variations in size and shape and changes with age, the uterus was subjectively evaluated. An enlarged or bulky uterus for age was considered to be of moderate importance. Calcifications in a normal-sized uterus were considered to be of minor importance.
Ovaries.—Ovarian masses of cystlike appearance were considered to be of minor importance when less than 3 cm in diameter and of moderate importance if 3 cm or larger in women older than 50 years. Masses less than 3 cm that were not clearly cystic were considered to be of moderate importance.
Aorta.—In patients 65 years or older, the diameter of the abdominal aorta was assessed by visual inspection; in cases of suspected aortic dilatation, the aortic diameter was measured using electronic calipers. In patients younger than 65 years, the aortic diameter was measured. Aortic aneurysm was defined as an infrarenal aortic diameter of 30 mm or more in patients 65 years old or older and 25 mm or more in patients younger than 65 years [12]. Aortic aneurysm was considered to be of major importance.
Lymph nodes.—Abdominal, retroperitoneal, and pelvic lymph nodes were classified as abnormal if the maximum short-axis diameter (largest measurement perpendicular to the long axis) was greater than 10 mm, and inguinal nodes were considered abnormal if greater than 15 mm. Nodes measuring 10 mm or less were considered abnormal if located adjacent to a bowel tumor (suspected metastases) or in a presacral, paracervical, or perirectal location, where lymph nodes are rarely seen normally. Clusters of normal-sized lymph nodes were considered abnormal [13]. Lymphadenopathy was regarded to be of major importance (suspected metastases) if associated with suspected malignancy (colorectal or other), of moderate importance if associated with findings suggestive of inflammatory bowel disease, and of minor importance if unrelated to such findings and of mild degree.
Free Abdominal Air
A rigorous search for free intraperitoneal or retroperitoneal air and
intramural bowel air was made in each patient (using lung CT window setting)
to rule out the possibility of air leaking into these compartments after
rectal air insufflation.
Follow-Up
To determine the clinical significance (diagnostic and therapeutic actions)
of the extracolonic CT findings, a search for clinical and radiologic
follow-up data (until April 2002) was performed in all patients with
extracolonic CT findings considered to be of moderate or major importance. All
but four of the 111 patients had given consent for a review of patient records
(two of these four patients had only extracolonic findings classified as
minor). If the patient was referred from the university hospital, relevant
patient records were searched and scrutinized. If no information was obtained,
or if the patient had been referred from an outside institution (hospital,
outpatient clinic, or general practitioner), the referring physician was
approached by mail, requesting follow-up data relevant to the CT colonography
findings. If no reply was obtained, a reminder letter was sent, and if
necessary the physician was contacted by telephone. If no information was
obtained, relevant patient records from hospitals and outpatient clinics
involved in the patient care were searched. A computerized radiology
information system common to the major hospitals in the area was searched for
results of radiologic examinations. An effort was also made to determine
whether any abnormalities identified on CT colonography were known before the
CT colonography examination.
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CT Findings of Moderate Importance
Fifty-eight (52%) of the 111 patients had CT findings of moderate
importance. In 15 of these, only moderate findings were present, whereas 24
had moderate and minor findings; 13 had moderate, minor, and major findings;
and six had moderate and major findings. In total, 83 CT findings were
classified as moderate (Tables
2 and
4).
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CT Findings of Major Importance
CT findings classified as major were discovered in 26 (23%) of the 111
patients. These 26 patients had a total of 37 major findings; 19 had a single
major finding, four had two major findings, two had three findings, and one
had four major findings (Tables
2 and
5).
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CT Findings of Moderate or Major Importance
Findings of moderate or major importance were made in 65 (59%) of the 111
patients. In total, 120 findings of moderate or major importance were made in
these patients. Eighteen of these findings (17 patients) were related to the
biliary tree (16 cases of gallstone and two cases of bile duct dilatation), 17
findings were definite or suspected renal masses (14 patients), 11 hernias
(seven hiatal hernias (Fig. 1A,
1B), three abdominal wall
hernias, and one inguinal hernia), 11 definite or suspected hepatic masses (11
patients), 12 adrenal masses (10 patients), nine cases of lymphadenopathy, six
aortic aneurysms, six uterine enlargement or myoma, and five mild
splenomegaly.
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Free Abdominal Air
No evidence of free intraperitoneal or retroperitoneal air or intramural
air was found in any of the patients.
Follow-Up of Moderate or Major Findings
Of the 65 patients with findings classified as moderate or major on CT
colonography, two did not give consent to a review of patient records. Of the
remaining 63 patients, 58 (92%) had radiology reports in the radiology
information system dated before the date of CT colonography, and 56 (89%) had
reports dated after the date of CT colonography. In total, 61 (97%) of 63
patients had reports dated before or after CT colonography.
Aortic aneurysm.—Six patients had abdominal aortic aneurysms measuring 63, 60, 40, 39, 37, and 34 mm. One of the patients did not allow patient record review. Two of the aneurysms were known before CT colonography, and one of these patients had previously undergone surgery for ruptured aortic aneurysm. One patient (Fig. 2) with a previously unknown 63-mm aneurysm had elective aneurysm surgery performed during follow-up.
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Hepatic lesions.—One of the five patients with hepatic lesions classified on CT colonography as being of major importance did not allow review of patient records. The other four patients had follow-up with CT or sonography or both. Hepatic metastases, suggested by our interpretation of CT colonography in three cases, were confirmed at follow-up in all cases. One case, classified on CT colonography as suspected solitary solid hepatic mass, was shown at follow-up to be focal fatty infiltration (i.e., a benign lesion). Hepatic metastases were unknown before CT colonography in one of the three cases with metastases revealed on CT colonography.
Six hepatic lesions (three indeterminate solitary masses and three cases of hepatic steatosis with irregular texture or suspected sparing) were classified on CT colonography as of moderate importance. Of these, two had follow-up imaging (CT and sonography in both cases and biopsy during surgery in one case). Of the three indeterminate hepatic masses on CT colonography, one was found at follow-up to be a cyst, one was a previously known steatosis, and another indeterminate 24-mm cyst-like hepatic mass with wall thickening had no follow-up. One of the two cases of hepatic steatosis with irregular texture on CT colonography was found to be metastatic from colon carcinoma, and the other was a previously known steatosis. The case of hepatic steatosis with suspected sparing had no follow-up data.
Gallstones.—Of the 16 patients with gallstones, 15 gave consent for review of patient records. In seven of the 15 patients, the gallstones were unknown before CT colonography (Fig. 1A, 1B).
Pancreatic lesions.—Two cases of definite or suspected pancreatic mass were classified on CT colonography as major findings. Both were followed up by contrast-enhanced CT. One case was confirmed as a previously unknown pancreatic cancer (Fig. 3) with hepatic metastases, and the other case was found to be normal.
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Two cases of pancreatic abnormalities were classified as of moderate importance, one case with parenchymal calcifications and duct dilatation compatible with chronic pancreatitis that was known before CT colonography, and one case of previously unknown parenchymal calcification with unknown clinical significance, without follow-up.
Adrenal lesions.—Adrenal masses occurred in 10 (9%) of the 111 patients. The median size (largest diameter) of the 12 adrenal lesions (in 10 patients) was 19 mm (range, 11–39 mm). All but two lesions had attenuation values of 10 H or less (benign lesions) (Fig. 4); two indeterminate lesions measured 13 and 18 H, respectively. One case of unilateral, moderate adrenal hyperplasia was classified as benign. The adrenal masses were unknown before CT colonography in all but one case. Follow-up CT was performed in five patients, in no case revealing progression or new diagnostic features. Four patients had no follow-up and one patient did not allow review of patient records. Four of the 10 patients with adrenal masses had malignant disease (carcinoma of the colon in two cases, pancreatic carcinoma, and generalized malignancy). Follow-up CT did not suggest a malignant cause of the adrenal lesions in any of these cases. No information was available on adrenal hormonal analysis in any of the cases.
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Kidneys and urinary tract.—Four patients had suspected solid renal mass lesions that were classified as major findings on CT colonography. Three of these had follow-up studies (CT and sonography in two and only CT in one) that revealed cysts in two cases and a solid 12-mm tumor in one case (Fig. 5) that was unchanged in size on CT and MRI follow-up. The tumor was not known before CT colonography. The fourth case was a 15-mm mass with irregular attenuation with no follow-up.
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Among the findings of moderate importance on CT colonography, three cases of angiomyolipoma were noted, none of which was known before CT colonography. Nine patients had 10 indeterminate renal masses, three of which had CT characteristics suggestive of hemorrhagic cysts. These findings were confirmed at follow-up sonography in two cases, but the third case was unconfirmed. The other seven indeterminate masses were followed up by sonography in four cases, showing cysts in three cases and no abnormality in one case; one lesion was known before CT colonography to be a cyst; and two lesions (7 and 10 mm) had no follow-up.
Extracolonic Findings in Patients With or Without Malignant Disease
Twelve (11%) of the 111 patients had malignant disease at the time of CT
colonography. One patient had widespread metastases from a previously resected
colon carcinoma, 10 patients had carcinoma of the colon, and one had
pancreatic cancer, all of which were detected on CT colonography. Extracolonic
CT findings of major importance occurred in nine (75%) of the 12 patients with
malignant disease, as compared with 17 (17%) of the 99 patients with no known
malignant disease. Sixteen (43%) of the total of 37 major findings were made
in the 12 patients with malignant disease. Similarly, CT findings of moderate
or major importance occurred in 11 (92%) of the 12 patients with malignant
disease, as compared with 54 (55%) of the 99 patients with no known malignant
disease. Patients with malignant disease had 28 (24%) of the 118 CT findings
of major or moderate importance, although they numerically constituted only
11% of the entire study group.
Major Extracolonic Findings—Missed Lesions and False-Positive Findings
The evaluation was based on available data at completion of the study,
including radiologic and clinical follow-up information.
Missed lesions.—One case of soft-tissue thickening in the left side of the pelvis of a patient with rectal cancer was missed on CT colonography. A tumor mass of increased size, representing tumor spread, was apparent on follow-up CT and could be seen retrospectively on the preceding CT colonography. In another case of rectal cancer, hepatic steatosis with irregular texture was seen on CT colonography and was considered to be of moderate importance, although follow-up CT was recommended. Follow-up CT and subsequent surgery showed hepatic metastasis.
False-positive findings.—Seven cases of false-positive major findings on CT colonography were identified. Two of these were suspected renal masses on CT colonography, but follow-up with contrast-enhanced CT revealed benign renal cysts in both cases (one was previously known). However, both of these patients had other major findings. One case of suspected solid pancreatic mass (major importance) on CT colonography turned out to be normal on follow-up CT, and another case was classified as a suspected solid hepatic lesion (major importance) on CT colonography but was shown to be focal fatty infiltration at follow-up. In seven patients, CT colonography revealed enlarged lymph nodes suggestive of malignant lymphadenopathy and classified as major findings. However, in three of these patients, two with colon carcinoma (Dukes' classification A) and one with colon carcinoma in situ, histologic analysis showed no malignant infiltration in the excised lymph nodes, and merely lymphadenitis in one case.
Overall Identification of Patients with Abnormalities of Major Importance
CT colonography suggested major findings in 26 patients, and in 19 patients
these findings were previously unknown (one patient did not allow review of
medical records). Seven of the patients had false-positive CT findings.
However, two of these patients had other major findings. Thus, in 14 (13%) of
111 patients, CT showed previously unknown major findings that were either
definite findings on CT, confirmed by follow-up, or not subjected to
(conclusive) follow-up.
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The high incidence of extracolonic findings in our study could partly be explained by the selection of patients, because we had a predominance of patients with moderate to high clinical suspicion of colon abnormalities. Thus, 10 patients had carcinoma of the colon, one had metastases from previously resected colonic carcinoma, and one had pancreatic cancer, all of which were detected on CT colonography. Extracolonic CT findings classified as major were markedly overrepresented in patients with malignant disease (9/12, 75%) as compared with those with no known malignant disease (17/99, 17%). By definition, patients with malignant disease accounted for all metastatic lesions and for most lymphadenopathy cases, and diagnoses unrelated to malignant disease were more evenly distributed.
The impact on the patient's care and wellbeing from identifying incidental findings with less clinical significance is difficult to assess, as pointed out by Westbrook et al. [14]. Gallstones were identified in 16 patients, and in seven of these the diagnosis was unknown before CT colonography. Nine patients had indeterminate renal masses that led to diagnostic follow-up in six cases; and 10 patients had adrenal masses (nine of which were previously unknown) and could be candidates for hormonal screening and further workup. The benefits and cost-effectiveness of identifying such lesions and others, such as indeterminate hepatic lesions that need diagnostic workup to prove nonmalignancy, renal angiomyolipomas that may need follow-up for growth, hiatal hernias, myomas, and other lesions, are not evident [14]. In some cases, such findings may reveal an explanation for a symptom or complaint, but in other cases no clear benefit will be obtained.
Another important aspect of incidental findings is the influence of age. With an aging population and an increased use of cross-sectional imaging, an increasing number of small incidental findings is likely to be revealed. The body changes with age, and normal CT findings in a 20-year-old individual may be different from normal findings in an 80-year-old individual, taking into consideration age-related changes such as degeneration, atrophy, and atherosclerosis. In addition, solid lesions in the parenchymal organs, including fibromas and other benign lesions, as well as clinically silent small malignant tumors indistinguishable from benign lesions, tend to increase with age. High-resolution cross-sectional imaging and possibly biochemical or molecular imaging have important roles in clarifying the natural course and characterization of these clinically silent, small solid lesions of benign and malignant causes.
Importance of IV Contrast Enhancement for Diagnostic Accuracy
For the purpose of colon evaluation, the CT examinations in our study were
performed with relatively small slice thickness (5 mm) and image
reconstruction intervals (2 mm) that are not always used in routine abdominal
CT. The analysis of extracolonic findings was also facilitated by the
availability of both supine and prone data sets and by the use of a
workstation for image interpretation, using cine mode image presentation to
facilitate anatomic orientation and dynamic CT window settings whenever
needed. However, because all CT was performed without IV contrast medium, the
characterization of many lesions was still difficult, leading to unnecessary
follow-up in some patients. Ambiguous findings, such as lesions that could be
either cystic or solid, were most common in the kidneys and liver.
Identification of aortic aneurysms, gallstones, abdominal wall hernias, hiatal
hernias, hepatic steatosis, and renal calcifications did not require contrast
enhancement. The use of IV contrast enhancement would probably have reduced
the number of false-positive major findings (two cases of renal cysts, one
normal pancreas, and one case of focal fatty infiltration in the liver were
classified as suspected solid masses). IV contrast enhancement may be
advantageous in the identification of colonic lesions on CT colonography
[15]. Contrast enhancement has
the added advantage of facilitating the evaluation of extracolonic tissues,
which reasonably reduces the need for follow-up examinations of questionable
parenchymal lesions. Thus, taking into account the added risk of contrast
media–induced renal failure and hypersensitivity, it seems reasonable to
use IV contrast enhancement on CT colonography in symptomatic patients.
Effects of Reduced Radiation Dose
To date, most authors agree that scanning the patient in both the supine
and prone positions is necessary for adequate visualization of the bowel wall
on CT colonography, because a change in body position allows intraluminal
fluid, stool, and air to be redistributed
[7,
16]. Double scanning means a
double radiation dose, an issue of particular importance in younger patients
and in screening. Efforts have been made to reduce the radiation dose on CT
colonography by reducing the X-ray tube current. Because of the high contrast
between the air in the colon and the adjacent bowel wall, the colon wall
evaluation is relatively insensitive to a reduction of the radiation dose
[17]. However, a lowered tube
current is accompanied by an increase in image noise that may negatively
affect the ability to evaluate extracolonic soft tissues, including the
detection and characterization of abnormalities in the solid abdominal organs.
Our study was performed at about half the standard abdominal CT radiation dose
(125 vs 250 mAs); subjectively, we did not experience any apparent problems
with image noise.
To our knowledge, extracolonic findings on CT colonography have been evaluated in two previous studies [6, 18], both performed at 70 mAs. Although inclusion criteria were not identical, both studies included patients having a high risk for colon disorders, and the mean patient ages (64 years and 65 years, respectively) and the CT techniques were comparable (Table 1). Interestingly, these two studies found a wide discrepancy in the frequency of extracolonic findings (Table 2). In the study by Hara et al. [6], 41% of the patients had incidental extracolonic findings, and in 11% these were considered to be "highly important lesions." In the study by Edwards et al. [18], the overall frequency of incidental extracolonic findings was 15%, and most findings turned out to be benign and of little clinical importance. This discrepancy may be related to differences in patient selection, definitions, and reporting threshold of extracolonic abnormalities. Thus, the proportion of patients with malignant disease, which may affect the frequency of extracolonic abnormalities, was not stated in these studies. We found extracolonic CT abnormalities of moderate or major importance to be much more frequent (59%) on CT colonography performed at 125 mAs. The low radiation dose levels in the studies by Hara et al. and Edwards et al. might have influenced the detection rate of extracolonic parenchymal lesions. However, because none of those studies included a comparison of the effects of standard versus low tube current, the role of lowered tube current in the evaluation of extracolonic soft tissues has not been resolved. If low-enough tube current is used, the opportunity to evaluate the extracolonic solid organs will be reduced or lost as a result of image noise. Likewise, if only the endoluminal images (i.e., the actual virtual colonoscopy) are used for colon diagnosis, extracolonic evaluation will not be part of CT colonography. Such a strategy may theoretically solve the question of the liability of the radiologist to identify and report extracolonic abnormalities. However, at present the axial source images remain an integrated and important part of the diagnostic evaluation of the colon, and as long as sufficient tube current is used for adequate evaluation of extracolonic findings, the extracolonic information available to the radiologist can hardly be ignored. The difficulties in distinguishing among normal variants, small benign lesions, and small malignant lesions remain. Similarly, the appropriate reporting threshold (i.e., what lesion size, characteristics, and diagnostic confidence levels should be applied) remains unclear. Further studies of these issues are needed before a definite and comprehensive evaluation of CT colonography for clinical and screening purposes can be made.
Screening Issues
Although not directly applicable to a screening situation, the results of
our study raise several issues pertinent to screening. Colon cancer is a
disease that appears suited to screening
[19,
20]. Several studies have
shown a reduced mortality with fecal occult blood screening followed by
combinations of barium enema, sigmoidoscopy, and colonoscopy, including
removal of polyps that may precede the development of colon cancer
[21–23].
However, one problem encountered in such screening is poor compliance
[24]. CT colonography has been
mentioned as a possible tool for screening
[25] because of better patient
acceptance than the prevailing examinations
[26]. In a CT colonography
screening perspective, incidental findings not related to the colon or to the
patient's symptoms constitute a potential major concern, and a defined
strategy for the clinical handling of such findings is necessary. The
frequency of extracolonic findings on CT colonography in a screening
population is unknown, but it may be lower than in our study and the study by
Hara et al. [6] because
malignancies can be anticipated at a lower frequency. On the other hand, the
frequency of abdominal aortic aneurysms (5%) in our study corresponds well
with that of sonography screening studies in populations of a similar age
[12]. Because general
screening of men for aortic aneurysm in the 50- to 60-year age group has been
advocated [12], simultaneous
screening with CT colonography for colon disorders and aortic aneurysm may be
beneficial. However, before CT colonography can be applied in a screening
situation, not only the diagnostic, economic, and logistic issues must be
considered, but also the ethical issues associated with the detection of
lesions in symptom-free individuals. Further studies of the benefits and
consequences of identifying both colon lesions and incidental extracolonic
abnormalities in screening populations are needed.
Conclusion
Incidental extracolonic findings on CT colonography were common in our
study and were mostly of minor importance. However, in a substantial number of
CT colonographies, potentially important findings were revealed that led to
additional diagnostic actions or therapeutic interventions. Some of these
findings were clinically important, but others led to unnecessary further
workup. These factors must be taken into account when evaluating the role of
CT colonography in routine diagnostic workup and in screening.
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