Chronic diverticulitis vs. colorectal cancer: findings on CT colonography

Chronic diverticulitis vs. colorectal cancer:findings on CT colonography

Stefaan Gryspeerdt, Philippe Lefere

Virtual Colonoscopy Teaching Centre, Akkerstraat 32 c, 8830 Hooglede, Belgium

Abstract

Purpose: The purpose of this update article is to evaluatefindings on CT colonography in patients with chronicdiverticulitis and to compare the findings in patients withcolorectal carcinoma.Materials and methods: Different morphological criteriaretrieved from a literature review were retrospectivelyanalyzed in a series of 13 patients with proven chronicdiverticulitis. The findings were compared with a seriesof 10 patients with colorectal carcinoma.Results: Overall, the findings in chronic diverticulitisresemble the findings in acute diverticulitis. The advan-tage of virtual CT colonography in differentiating bothentities relies in the combination of morphologicalfeatures previously described on axial computed tomog-raphy and double contrast barium enema. The singlestrongest morphological feature pointing towards thediagnosis of chronic diverticulitis is the presence ofdiverticula in the affected segment. In the presence ofdiverticula in the affected segment, a long segment(‡10 cm), thick fascia sign without adenopathies, mildbowel wall thickening, tapered margins, and distortedbut preserved mucosal folds are likely to further improveaccuracy of diagnosing chronic diverticulitis.Conclusion: The single strongest morphological sign todifferentiate chronic diverticulitis from colorectal canceris the presence of diverticula in the affected segment.

Key words: Diverticulitis—Chronic—Tumor—Colon—Virtual CT colonoscopy

In Western countries the presence of diverticular diseasehas increased over the past century. The prevalence ofdiverticulosis is similar in man and woman, increasingwith age ranging from approximately 10% in adults

younger than 40 years of age to 50–70% among those80 years of age or older [1–7].

The terms diverticulosis and diverticular disease areused to describe the presence of an uninflamed divertic-ulum.

Diverticulitis indicates inflammation of the divertic-ulum, accompanied by gross and microscopic perfora-tion. It is a common condition with an estimatedincidence of 25%. Of those patients who experience anattack of diverticulitis one-third will have recurrentsymptoms and another third will have a subsequentepisode [8–10].

The inflammatory changes and associated fibrosis causedistortionof thebowelwall.AbdominalCThasbeenshownto reveal wall thickening and pericolic inflammatorystranding and associated inflammatory collections or ab-scesses in patients with colonic diverticulosis associatedwith one or more episodes of diverticulitis [11].

The main difficulty in the diagnosis of diverticulitis,being it acute, recurrent or chronic, is to exclude thepossibility of colon cancer: both diseases are endemic inthe aged population and results of previous studies haveindicated that there is an overlap in the CT appearancebetween acute diverticulitis and colorectal cancer. Eventhe combination of findings results frequently inunequivocal differentiation between acute diverticulitisand tumor [12–19].

Toourknowledge there has beenonlyone limited reportdescribing chronic diverticulitis on CT [20] and doublecontrast barium, with no report describing the appearancesof chronic diverticulitis on virtual CT colonography.

It is the purpose of this article to review and deter-mine CT signs helpful in differentiating between chronicdiverticulitis and colon cancer.

Materials and methods

In the first part a review of the literature was performedto identify different signs of diverticulosis/diverticulitis,possibly useful to differentiate chronic or recurrent div-erticulitis from colorectal cancer.

Correspondence to: Stefaan Gryspeerdt; email: [email protected]

ª Springer Science+Business Media, LLC 2012

AbdominalImaging

Abdom Imaging (2012)

DOI: 10.1007/s00261-012-9858-6

Patients

In the second part of the study we retrospectively re-viewed the reports of virtual CT colonography studiessent for review to a tele-radiology site in Hooglede,Belgium, between 2008 and 2010. All examinations wereinterpreted and reported in consensus by two radiologistswith an experience of >5000 CTC (S.G. and P.L.).

Based on these reports, studies that showed imagingfindings compatible with chronic diverticulitis, sigmoidalcancer or studies that concluded equivocal findings ofchronic diverticulitis or sigmoidal cancer were retrieved.

The medical data of these patients were retrospec-tively evaluated and final diagnosis of chronic divertic-ular disease as well as the exclusion or presence of coloncancer was considered confirmed by means of the fol-lowing: clinical course and ultimate clinical outcome inthe patient at medical chart review performed at least 2years after virtual CT colonography, colonoscopy, andbiopsy, or surgery.

CT scanning

All patients underwent a colonic preparation consistingof a low residue diet, cathartic colon cleansing, and fecaltagging with barium and iodine. After smooth musclerelaxation with buthylscopalamine (Buscopan, Boeh-ringerIngelheim, Paris, France) colonic insufflation wasobtained with an automated carbon dioxide insufflator(PROTOC02L, E-Z-EM, Princeton, USA).

Data were obtained with patients in the supine andprone positions. All examinations were performed withmultidetector-row CT scanners that had a minimum offour rows.

Review of images

Data of eligible patients were reloaded on a dedicatedworkstation (Vitrea, version 6.0, Vital Images, Plym-outh, MN).

All images were reviewed for radiographic imagingfindings identified on the basis of literature review. Axial,coronal, and sagittal images, as well as tissue transitionprojection (TTP) images were used.

Results

Review of literature

Review of the literature revealed following signs possiblyhelpful in differentiating chronic diverticulitis fromcolorectal cancer on virtual CT colonography: involvedlength [16], presence or absence of diverticula (normal orinflamed, with or without arrowhead sign in the affectedsegment [17, 18]), degree of luminal narrowing [19],pericolic infiltration [17] (grouping imaging features de-scribed as stranding and pericolic edema [16]), thick

fascia sign [18], lymph nodes and lymph nodes size [16],wall thickness and pattern of thickening (luminal mass[19], concentric wall thickening or eccentric wall thick-ening [17]), morphology of the margins (tapered or cone-shaped vs. abrupt with shoulder forming) [20], mor-phology of the mucosal folds (distorted but preserved ordistorted) [20], intestinal obstruction [20].

Pathology typically associated with chronic recurrentdiverticular disease: mucosal prolapse syndrome andinflammatory polyps [21].

The degree and patterns of contrast enhancement(target sign or halo sign, homogeneous, heterogeneous[22]), as well as visualization of engorged mesenteric veins[17] have also been described as differentiators betweencolonic diverticulitis and colon cancer but were not with-hold for this study since no contrast was administered inany of the virtual CT colonography examinations.

Signs typically found in the setting of acute divertic-ulitis were not withhold for analysis because our purposewas the evaluation of signs present in chronic/recurrentdiverticulitis, and, more importantly, in the setting ofvirtual CT colonography, none of the patients presentedwith acute abdominal pain or tenderness suggestive foracute diverticulitis. Therefore, the following signs werenot tabulated for evaluation: free fluid, free air, ab-scesses, fistulae. All these signs are typically seen in thesetting of acute diverticulitis [18–20].

Patients

Based on retrospective analysis of the reports that showedimaging findings compatible with chronic diverticulitis,sigmoidal cancer or studies that concluded equivocal find-ings of chronic diverticulitis or sigmoidal cancer, we wereable to retrospectively withhold a confirmed diagnosis oftumor or chronic diverticular disease in 23 patients.

Based on medical data, clinical course, and ultimateclinical outcome a confirmed diagnosis of chronic div-erticulitis was found in 13 patients: exclusion of coloncancer by negative clinical follow-up during at least 2years in 5 patients, biopsy showing chronic inflammatorydisease in another 5 patients. Chronic diverticulitis wasdiagnosed in 3 patients at surgery.

In 10 patients final diagnosis of colorectal cancer wasestablished at surgery.

Analysis of CT findings

The prevalence of the findings studied is shown inTables 1 and 2 for patients with final diagnosis ofchronic diverticulitis and carcinoma, respectively.

Calculated sensitivity, specificity, positive predictivevalue, negative predictive value, and accuracy are detailedin Table 3.

Although the series are definitely too small to getenough statistic power (reflected in a wide range of lower

S. Gryspeerdt, P. Lefere: Chronic diverticulitis vs. colorectal cancer

and upper limits, tabulated in Table 3), we were able toretrieve some clear tendencies (Figs. 1, 2, 3, 4).

Single morphological features. When we evaluate singlemorphological signs, a single strong discriminator wasthe presence or absence of diverticula in the affectedsegment. Presence of diverticula in the involved segmentwas found in all but one (92%) patients in the group ofchronic diverticulitis whereas diverticula in the involvedsegment were found in none of the patients with finaldiagnosis of colon carcinoma. Presence of diverticula inthe affected segment showed 92% sensitivity, 100%

specificity, 100% positive predictive value, 91% negativepredictive value, and 96% accuracy for chronic divertic-ulitis. The series evaluated is, however, small, resulting ina relative wide range of lower limits (Table 3).

Other morphological criteria

None of the tumors showed preserved mucosal folds;whereas mucosal folds were judged preserved in 76% ofcases with chronic diverticulitis.

Chronic diverticulitis tended to be longer compared totumor: the mean length for chronic diverticulitis was 11 cm,compared to 3.4 cm for tumors.Whenwe arbitrarily dividedgroups in lesions ‡10 cmand<10 cm, a 100% specificity forchronic diverticulitis is obtained for lesions ‡10 cm.

Complete luminal narrowing on virtual CT colonog-raphy was found in 40% of patients for both groups.

Pericolic infiltration was indicative for chronic div-erticulitis rather than tumor, being present in 85% ofpatients with chronic diverticulitis, compared to 60% inthe group of patients with tumoral disease.

Thick fascia sign was found to be a strong discrimi-nator, being present in 77% of patients with chronicdiverticulitis compared to only 10% of patients with tu-moral disease.

Lymph nodes with variable diameter ranging from 2to 10 mm were found in 38% of patients with chronicdiverticulitis, whereas larger lymph nodes with variablediameter ranging from 7 to 10 mm were found in 60% ofpatients with tumoral disease.

Bowel wall thickening was more pronounced in thegroup with tumoral disease (mean 17 mm) compared to

Table 1. Prevalance of findings on virtual CT colonography in patients with chronic diverticulitis

Chronic diverticulitis 1 2 3 4 5 6 7 8 9 10 11 12 13 Av/%

Length (mm) 70 58 80 70 90 270 36 230 60 107 250 91 59 113 mmDiverticula in affected segment x x x x x x x x x x x x 92%Luminal narrowing (mm) Complete Complete 7 Complete complete 13 10 8 Complete 23 10 5 9Pericolic infiltration x x x x x x x x x x x 85%Thick fascia sign x x x x x x x x x x 77%Lymph nodes (if present max. size mm) 10 6 6 8 6Bowel wall thickening (mm) 22 17 17 10 10 10 14 9 13 8 7 15 6 12 mmLuminal mass x 30%Concentric wall thickening x x x x x 41%Eccentric wall thickening x x x x x x 41%Tapered margins x x x x x x x x 67%Overhanging edge—shoulder forming x x x x x 38%Distorted but preserved mucosal folds x x x x x x x x x x 85%Distorted mucosal folds x x x 23%Mucosal prolapse xInflammatory polyp x

Av average

Table 2. Prevalance of findings on virtual CT colonography in patients with colorectal cancer

Cancer 1 2 3 4 5 6 7 8 9 10 Av/%

Length (mm) 45 89 18 32 28 39 27 40 25 5 34 mmDiverticula in affected segment 0%Luminal narrowing (mm) 12 7 17 Complete 3 Complete Complete 19 26 CompletePericolic infiltration x x x x x x x 60%Thick fascia sign x 10%Lymph nodes (if present max. size mm) 10 6 8 8 7 8Bowel wall thickening (mm) 22 14 9 17 16 8 13 22 27 23 17 mmLuminal mass x x 20%Concentric wall thickening x x x x x 50%Eccentric wall thickening x x x x 40%Tapered margins x 10%Overhanging edge—shoulder forming x x x x x x x x 90%Distorted but preserved mucosal folds 0%Distorted mucosal folds x x x x x x x x x x 100%

Av average


the group with chronic diverticulitis (mean 12 mm).Bowel wall thickening of more than 2 cm was found in30% of tumoral lesions compared to only 0.1% in thegroup with chronic diverticulitis. Eccentric wall thick-ening and tapered margins were present in, respectively,46% and 67% patients with chronic diverticulitis vs. 40%

and 0% in patients with tumoral disease.Overhanging edges or shoulder formation was found

in all but 2 patients with tumoral disease (90%) (identi-fied mainly on the basis of TTP images), and in only 38%

of patients with chronic diverticulitis.Interestingly, we did not find signs of obstruction in

any patient at time of virtual CT colonography.Finally, pseudopolypoid images (caused by mucosal

prolapse) and inflammatory polyp were both found in asingle different patient with final diagnosis of chronicdiverticular disease.

Combined morphological signs. The number of subjectswas too low to perform multivariable analyses. Indeed, aminimum of 10 subjects in the least occurring categoryper independent variable has been recommended [23].Inclusion of too many predictors leads to overfitting ofthe data.

Indeed, in a smaller series a perfect diagnostic accu-racy can often be obtained combining different findings.In this study, an excellent accuracy (96%) was observed

with a single finding, i.e., ‘diverticula in affected seg-ment’. To obtain such high accuracy level in a largerseries, adding information from other findings could berequired.

The results indicate findings which are candidates asadditional predictors.

Following findings showed an accuracy >70%:presence or absence of thick fascia sign and evaluation ofthe mucosal folds (preserved or distorted).

Other findings showed an accuracy >50%: evaluationof the length of the affected segment (< or ‡10 cm),presence or absence of adenopathies, bowel wall thick-ening (< or ‡2 cm), margins of the lesions (tapered orshoulder forming.

Discussion

Diverticular disease and colorectal neoplasia share sim-ilar epidemiological features and risk factors. An in-creased risk for sigmoid location of tumors in patientswith diverticula as compared to comparable groups hasbeen reported. Similarly, the prevalence of advancedadenomas in the sigmoid colon has been reported as wellas the association of diverticulosis with colorectal neo-plasia. A common explanation for the similar develop-ment of diverticulosis and colorectal neoplasia is relatedto the slow colonic transit time for both conditions.

Table 3. Statistical analysis of findings on virtual CT colonography for chronic diverticulitis and colon cancer

Sensitivity Specificity PPV NPV Accuracy

LL UL LL UL LL UL LL UL LL UL

Chronic diverticulitisLength (>10 cm) 0.31 0.09 0.61 1.00 0.69 1.00 1.00 0.40 1.00 0.53 0.29 0.76 0.61 0.39 0.80Diverticula in affected segment 0.92 0.64 1.00 1.00 0.69 1.00 1.00 0.74 1.00 0.91 0.59 1.00 0.96 0.78 1.00Luminal narrowing (complete) 0.38 0.14 0.68 0.60 0.26 0.88 0.56 0.21 0.86 0.43 0.18 0.71 0.48 0.27 0.69Pericolic infiltration 0.85 0.55 0.98 0.30 0.07 0.65 0.61 0.36 0.83 0.60 0.15 0.95 0.61 0.39 0.80Thick fascia sign 0.85 0.55 0.98 0.90 0.55 1.00 0.92 0.62 1.00 0.82 0.48 0.98 0.87 0.66 0.97Lymph nodes absent 0.62 0.32 0.86 0.60 0.26 0.88 0.67 0.35 0.90 0.55 0.23 0.83 0.61 0.39 0.80Bowel wall thickening (<2 cm) 0.92 0.64 1.00 0.40 0.12 0.74 0.67 0.41 0.87 0.80 0.28 0.99 0.70 0.47 0.87Luminal mass 0.08 0.00 0.36 0.80 0.44 0.97 0.33 0.01 0.91 0.40 0.19 0.64 0.39 0.20 0.61Concentric wall thickening 0.38 0.14 0.68 0.50 0.19 0.81 0.50 0.19 0.81 0.38 0.14 0.68 0.43 0.23 0.66Eccentric wall thickening 0.46 0.19 0.75 0.60 0.26 0.88 0.60 0.26 0.88 0.46 0.19 0.75 0.52 0.31 0.73Tapered margins 0.62 0.32 0.86 0.90 0.55 1.00 0.89 0.52 1.00 0.64 0.35 0.87 0.74 0.52 0.90Distorted but preserved mucosal folds 0.77 0.46 0.95 1.00 0.69 1.00 1.00 0.69 1.00 0.77 0.46 0.95 0.87 0.66 0.97

CancerLength (<10 cm) 1.00 0.69 1.00 0.31 0.09 0.61 0.53 0.29 0.76 1.00 0.40 1.00 0.61 0.39 0.80No diverticula in affected segment 1.00 0.69 1.00 0.92 0.64 1.00 0.91 0.59 1.00 1.00 0.74 1.00 0.96 0.78 1.00Luminal narrowing (incomplete) 0.60 0.26 0.88 0.38 0.14 0.68 0.43 0.18 0.71 0.56 0.21 0.86 0.48 0.27 0.69No pericolic infiltration 0.60 0.26 0.88 0.38 0.14 0.68 0.43 0.18 0.71 0.56 0.21 0.86 0.48 0.27 0.69No thick fascia sign 0.90 0.55 1.00 0.85 0.55 0.98 0.82 0.48 0.98 0.92 0.62 1.00 0.87 0.66 0.97Lymph nodes present 0.60 0.26 0.88 0.62 0.32 0.86 0.55 0.23 0.83 0.67 0.35 0.90 0.61 0.39 0.80Bowel wall thickening(>2 cm) 0.40 0.12 0.74 0.92 0.64 1.00 0.80 0.28 0.99 0.67 0.41 0.87 0.70 0.47 0.87Luminal mass 0.20 0.03 0.56 0.92 0.64 1.00 0.67 0.09 0.99 0.60 0.36 0.81 0.61 0.39 0.80Concentric wall thickening 0.50 0.19 0.81 0.62 0.32 0.86 0.50 0.19 0.81 0.62 0.32 0.86 0.57 0.34 0.77Eccentric wall thickening 0.40 0.12 0.74 0.54 0.25 0.81 0.40 0.12 0.74 0.54 0.25 0.81 0.48 0.27 0.69Overhanging edge—shoulder forming 0.90 0.55 1.00 0.62 0.32 0.86 0.64 0.35 0.87 0.89 0.52 1.00 0.74 0.52 0.90Distorted mucosal folds 1.00 0.69 1.00 0.77 0.46 0.95 0.77 0.46 0.95 1.00 0.69 1.00 0.87 0.66 0.97

Clopper–Pearson exact 95% confidence interval for a proportion (based on binomial distribution)LL lower limit, UL upper limit, PPV positive predictive value, NPV negative predictive value


Furthermore, there is the possibility that patients with aprior history of diverticulitis have a higher risk of colo-rectal carcinoma because of the chronic inflammation inthe mucosa contributing to carcinogenesis [24–26].

Although elective sigmoid resection is frequentlyrecommended after the two episodes of uncomplicateddiverticulitis because of the serious complications ofrecurrent colonic diverticulitis many authors have alsoshown that symptomatic patients, responding well tomedical treatment for uncomplicated diverticulitis,would be expected to do well without elective colectomy[8, 27, 28].

Since virtual CT colonography has gained acceptanceas possible examination tool for screening the patient ataverage risk for colorectal cancer and diverticular diseaseand colorectal neoplasia share similar epidemiologicalfeatures and risk factors, differentiating chronic orrecurrent diverticulitis from tumoral disease is likely tobecome more and more important.

There have been several studies describing the CTfeatures of diverticulitis and colon cancer. Many of thestudies described overlapping CT features of those twodiseases.

Review of the literature shows that significant pointsof overlap include wall thickening, associated soft tissuemasses, and luminal narrowing [12–14].

Fig. 1. Typical chronic diverticulitis: axial CT images. AxialCT images show a long segment with tapered margins (arrowin A), distorted but preserved folds (arrows in B), the thick

fascia sign (arrow in C), and the presence of diverticula in theaffected segment (arrow in D).

Fig. 2. Typical chronic diverticulitis: TTP image shows along segment with distorted but preserved mucosal folds(arrows).


Chintapalli [15] found that in case the length of theinvolved segment is more than 10 cm in the presence ofpericolonic stranding with no colonic lymph nodesadjacent to the segment, the most likely diagnosis isdiverticulitis. In case pericolonic lymph nodes are pres-ent, most likely diagnosis was reported to be coloncancer [14]. Our series confirmed that a long affectedsegment (‡10 cm) is more likely to be found in chronicdiverticulitis. We found a tendency of pericolic infiltra-tion suggesting chronic diverticulitis but could not find atendency of lymph nodes pointing towards diagnosis oftumoral disease. The latter can probably be explained bythe nature of chronic diverticulitis: chronic disease islikely to cause more adenopathies, detected by CT,compared to acute diverticulitis.

The finding of shoulder forming being suggestive fortumoral disease in our series is also in concordance withresults published by Chintapalli [16].

Kircher [18] reported pericolic infiltration (fatstranding) to be found in 95% of patients with divertic-ulitis, and thick fascia sign in 50% of patients. Compa-rably, we found pericolic infiltration or thick fascia signto be present in 75% of cases.

To our knowledge only one study reported uponradiographic findings in case of chronic diverticulitis [20].In that study barium enema examinations were reportedto reveal a relatively long segment of circumferentialnarrowing in the sigmoid colon with spiculated contourand tapered margins.

CT revealed findings of sigmoid diverticulitis withlocalized wall thickening and pericolic fat stranding in90% of the patients in whom CT was performed; CTrevealed inflammatory collections in three and fistulas inanother 3 patients.

Fig. 3. Typical tumor. A Typical axial image shows a shortsegment with pronounced wall thickening, shoulder forming,and no in-lying diverticula (arrows). B Virtual double contrast

barium enema images show short segment with shoulderforming and distorted mucosal folds (arrows).

Fig. 4. Usefulness of detecting in-lying diverticula for diag-nosing chronic diverticulitis. A TTP image shows short 3.6 cmsegment with preserved mucosal folds but shoulder formingat the proximal margin. Unequivocal findings: preserved foldsare indicative for chronic diverticulitis but short segment withshoulder forming indicates tumor. B Axial image demon-strates in-lying diverticula, one with presence of hyperdensefecalith (f), indicating chronic diverticulitis (arrows). Additionalfinding: thick fascia sign, also suggestive for chronic diver-ticulitis (arrowhead).


The authors concluded that the CT findings inpatients with chronic diverticulitis are similar to those inpatients with acute diverticulitis.

Our study confirmed that, based on axial imagingonly, the findings are in line with findings in patientspresenting with acute diverticulitis.

Findings suggestive of chronic diverticulitis.

1. Wall thickening (milder). 2. Long segment (> 10 cm). 3. Tapered margins. 4. Distorted but preserved folds. 5. Pericolonic infiltration. 6. No pericolonic adenopathies. 7. Thick fascia sign . 8. Diverticula adjacent to and in the

affected segment.

Findings suggestive of maligant tumor.

1. Wall thickening ++ (> 2 cm). 2. Short segment . 3. Shoulder forming. 4. Distorted folds. 5. No pericolonic infiltration. 6. Pericolonic adenopathies. 7. No thick fascia sign . 8. Diverticula adjacent to but NOT IN

the affected segment.

Fig. 5. Differential diagnosis between chronic diverticulitis and adenocarcinoma.


Using TTP images obtained at virtual CT colonography,our study confirmed that tapered margins and presence ofmarkedly separate spiculated folds without distortion pointtowards the diagnosis of chronic diverticulitis.

Obstruction has been reported in acute diverticulitis,tumor as well as chronic diverticulitis [18, 20].

In our series, however, none of the patients presentedwith signs of obstruction. The explanation for this is apatient selection bias residing in the fact that we exam-ined a cohort of patients examined with virtual CT col-onography, a recent technique not eligible to evaluatepatients with acute abdominal symptoms.

The most important discriminator to differentiatebetween chronic diverticulitis and tumoral disease,however, was the finding that in our small series thepresence of diverticula in the affected segment clearlypoints towards the diagnosis of benign disease ratherthan tumoral pathology. This finding was previouslydescribed by Shenet al. [17]. It is important to note thatdiverticula in close relation with the affected segmentwere found in both groups, (more precisely in 3 patientswith chronic diverticulitis and 2 with tumoral disease), afinding also reported by Shen et al.

In linewith the findings of other authors [16–18]we alsofound long segments being indicative for chronic diver-ticulitis, short segments being indicative for tumoral dis-ease. However, the high sensitivity for tumoral diseaseusing cut-off of 10 cm in this series is surprising and to beattributed to the small number of tumors, e.g., by chance.

Although our series is too small for multivariateanalysis, we can theoretically evaluate our results andlook for signs with accuracy >50% for both tumor andchronic diverticulosis. In this way it is reasonable to ex-pect that evaluation of the length of the affected segment,presence or absence of thick fascia signor adenopathies,bowel wall thickening, margins of the lesions, and eval-uation of mucosal folds further enhance the diagnosticcapability of presence or absence of diverticula in theaffected segment. Especially, evaluation of thick fasciasign and morphology of the mucosal folds are promisingcandidates as additional predictors.

Bringing together all signs, it seems reasonable totheoretically conclude that, in the presence of diverticulain the affected segment, a long segment (‡10 cm), thickfascia sign without adenopathies, mild bowel wallthickening, tapered margins, and distorted but preservedmucosal folds are likely to improve accuracy of diag-nosing chronic diverticulitis.

In the absence of diverticula, a short segment(<10 cm), absence of thick fascia sign, presence ofdiverticula, pronounced bowel wall thickening (>2 cm),shoulder forming, and distorted mucosal folds are likelyto improve the accuracy of diagnosing tumor (Fig. 5)

A combination of all these findings and multivariateanalysis would be worthy to be investigated in largerseries.

The use of combined findings of presence or absenceof lymph nodes, pericolonic inflammation and edemawere comparably found in the study by Chintapalli[15, 16].

This study has several serious limitations. First of allthis is a retrospective study with inherent selection bias aswell as well as interpretation bias. The small number ofpatients included in the series does not give the resultsenough statistical power. Therefore, we can only con-clude for tendencies. Furthermore, final diagnosis ofchronic diverticulitis is based on the mixture of clinical aswell as pathological basis. Therefore, we cannot excludethe presence of small slow-growing tumoral foci in whatclinically appears to be chronic diverticulitis.

However, our findings are consistent with previouslyreported series and show that the strength of virtual CTcolonography in differentiating chronic diverticulitisfrom tumoral disease relies in the combination of find-ings previously reported on axial computer tomographyas well as those reported on barium enema studies.

The single strongest morphological feature pointingtowards the diagnosis of chronic diverticulitis is thepresence of diverticula in the affected segment.

In the presence of diverticula in the affected segment,a long segment (‡10 cm), thick fascia sign withoutadenopathies, mild bowel wall thickening (<2 cm),tapered margins, and distorted but preserved mucosalfolds are likely to further improve accuracy of diagnosingchronic diverticulitis.

Acknowledgments. The authors acknowledge the following colleaguesfor their help with clinical follow-up of the patients: Leroux K, MDRadiology Department, Ziekenhuis Maas en Kempen, B-3680 Maaseik,Belgium; Ardies Ph, MD Radiology Department, AZ Sint-Jozef, B-2390 Malle, Belgium, Clybauw A, MD Radiology Department, AZMaria Middelares, B-9050 Gentbrugge, Belgium; Grignard F, MDRadiology Department, Sint-Elizabeth Ziekenhuis, B-9620 Zottegem,Belgium; Louagie A, MD Radiology Department, AZL AlgemeenZiekenhuis Lokeren, B-9160 Lokeren, Belgium; Perdieus D, MDRadiology Department, Imelda Ziekenhuis, B-2820 Bonheiden, Bel-gium; and Sieleghem D, MD Radiology Department, AZ Sint Blazius,B-9200 Dendermonde, Belgium. The authors also acknowledge FieuwsS, Ir, Biostatistical Centre, Katholieke Universiteit Leuven, Kapucij-nenvoer 35, B-3000 Leuven, Belgium for advice with statistical analysis.

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