MDCT assessment of ulcerative colitis:radiologic analysis with clinical, endoscopic,and pathologic correlation

Bijal Patel,1 Jeffrey Mottola,1 V. Anik Sahni,1 Vito Cantisani,1,3 Mehmet Ertruk,4

Sonia Friedman,2 Andrew M. Bellizzi,5 Andrea Marcantonio,1,3 Koenraad J. Mortele1

1Division of Abdominal Imaging & Intervention, Department of Radiology, Brigham and Women’s Hospital, Harvard Medical

School, Boston, MA, USA2Division of Gastroenterology, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston,

MA, USA3Department of Radiology, La Sapienza Hospital, Rome, Italy4Department of Radiology, Sisli Etfal Training and Research Hospital, Istanbul, Turkey5Department of Pathology, Brigham and Women’s Hospital, Boston, MA, USA

Abstract

Purpose: Evaluate the utility of multidetector-row com-puted tomography (MDCT) in assessing the severity ofulcerative colitis (UC) in comparison with clinicalassessment, colonoscopy, and histopathology.Materials and methods: Patients with UC evaluated withat least one abdominal contrast-enhanced CT study(CECT) within 7 days of colonoscopy with biopsy wereincluded. CECT of 23 patients (12 male; mean age40 years; age range, 20–72 years) were retrospectivelyevaluated in consensus by two radiologists. A total of138 lower GI tract segments were evaluated by CECTand graded for the presence of bowel wall thickening,mucosal hyperenhancement, mural stratification, mesen-teric hyperemia, pericolonic stranding, and lymph nodes.A cumulative CT severity score was calculated andcorrelated with clinical, colonoscopic, and histopatho-logic severity grades.Results: The cumulative CT score and individual CECTscores for bowel wall thickening, mucosal hyperenhance-ment, and mural stratification showed positive correla-tion with clinical severity (P < 0.05). All individualCECT features as well as the cumulative CT scoredemonstrated statistically significant correlation withcolonoscopic severity (P < 0.0001). Only wall thicken-ing on CECT demonstrated significant correlation withhistopathologic severity (P = 0.01).

Conclusion: Disease severity assessment by MDCTdemonstrates positive correlation with severity estab-lished by clinical assessment and colonoscopy. Onlyincreasing wall thickness, as graded on MDCT, corre-lates with histopathologic disease severity.

Key words: Ulcerative colitis—Multidetector-row CT(MDCT)—Colonoscopy—Pathologic

Inflammatory bowel disease (IBD) refers to a group ofintestinal disorders characterized by a relapsing andremitting course of bowel inflammation and extra-intestinal manifestations [1]. Crohn disease and ulcera-tive colitis (UC) account for the vast majority of IBD. Inup to 6% of cases, however, due to overlapping clinical,imaging, and histologic features, definitive distinc-tion between the two entities cannot be made and theterm ‘‘unclassified’’ or ‘‘indeterminate’’ colitis is used[2, 3].

The symptoms of UC are not specific and, therefore,initial assessment requires the combination of colono-scopic, histologic and sometimes radiologic evaluation[4]. Conventional optical colonoscopy combined withhistologic analysis represents the standard of referencefor the evaluation of UC [5]. Colonoscopy with mucosalbiopsy permits both direct visualization of colonic mu-cosa as well as tissue sampling, which can be used toassess for disease activity and severity as well as to screenfor colorectal carcinoma [5–7].Correspondence to: Bijal Patel; email: bpatel03@hotmail.com

ª Springer Science+Business Media, LLC 2011

Published online: 21 May 2011AbdominalImaging

Abdom Imaging (2012) 37:61–69

DOI: 10.1007/s00261-011-9741-x

Multidetector-row computed tomography (MDCT)has emerged as a valuable imaging method with a highsensitivity for evaluating intramural extension of colonicdisease [8]. In addition, MDCT has the ability to provideinformation with regard to extraintestinal manifestationsand complications [7]. Determination of disease severityprovides an important role in assessing therapeuticstrategy, treatment response, and prognosis. Despite thewide availability of MDCT and the prevalence of UC,there have been few studies in the literature illustratingthe MDCT features of UC [8, 9]. Moreover, to the bestof our knowledge, there have been no previous studiesthat have assessed the utility of MDCT to predict theseverity of UC, as assessed by symptoms, endoscopy, andhistology.

Therefore, the purpose of this study is to evaluate theusefulness of MDCT in determining the severity of UC incomparison with colonoscopy, histopathology, andclinical evaluation.

Materials and methods

Subjects

This Health Insurance Portability and AccountabilityAct-compliant retrospective study was approved by ourinstitutional review board; patient informed consent waswaived.

A review of the computerized lower endoscopy andpathology databases at our institution revealed a total of855 consecutive patients with UC diagnosed between1999 and 2007. All patients underwent lower endoscopicexamination, with biopsies of one or more segments ofthe colon to determine histopathologic disease severity.During 1999, before complete integration of MDCT atour institution, 24 of the 855 patients underwent singledetector CT studies, and were excluded from the study. Atotal of 198 (23%) patients had at least one abdominaland pelvic CT with a MDCT scanner (4-, 16- or 64-detector row). Among these patients, those who did notreceive IV contrast (n = 14) were excluded from thestudy. In three patients, the CT studies were not avail-able. Patients who had undergone colectomy and/or ileo-anal pouch surgery prior to the CECT (n = 42) werealso excluded from the study. Finally, patients with atime interval of greater than 7 days between the CECTexamination and biopsy (n = 116) were excluded fromthe study (Fig. 1).

A final study group of 23 patients (mean age:40 years; age range: 20–72 years) were included of which12 (52%) were male. The mean time interval between theCECT study and lower endoscopy with biopsy was2.4 days (range: 0–7 days). Of the 23 patients, 22 had aknown diagnosis of UC with a mean interval time of8.2 years (range 6 months to 20 years) from the initialdiagnosis to the colonoscopy with mucosal biopsy.Twenty patients presented with an acute flare of disease,

with one of these patients presenting for the first time. Ofthe three patients who did not present with acute exac-erbation, colonoscopy and biopsy were performed forroutine surveillance. In one of these patients, mucosalbiopsy demonstrated an invasive adenocarcinoma at thehepatic flexure, and a CECT was performed for stagingpurposes. In the other two patients CECT was per-formed, incidental to the colonoscopy, for pancreatitisand abdominal pain in the setting of known primarysclerosing cholangitis (PSC). Using our computerizedclinical information system database, presenting signsand symptoms of each patient prior to their CT wererecorded. Symptoms included abdominal pain (n = 16),fever (n = 8), nausea and vomiting (n = 3), intestinalbleeding (n = 3), diarrhea (n = 2), and elevated liverfunction tests (n = 1).

MDCT technique

Abdominopelvic CT scanning was performed usingMDCT units (Volume Zoom, and Volume Sensation,Siemens Medical Systems, Erlangen, Germany). CECTscans (slice thickness, 5 mm; reconstruction interval,5 mm) were obtained 60–70 s after IV administration of100 mL of 300 mg I/mL iopromide (Ultravist 300, BerlexLaboratories, Montvale, NJ), injected at a rate of3.0 mL/s using a power injector. Opacification of thedigestive tract was achieved in 21 (91%) patients afteroral administration of 900 mL of a high density bariumsulfate suspension agent (Readi-Cat, E-Z-EM, West-bury, NY) and in two patients after administration of1350 mL of neutral oral contrast material (0.1% weight/volume [w/v] barium sulfate suspension, Volumen, E-Z-EM). Oral contrast was administered approximately 2 hprior to the examination, in order to optimally opacifythe colon and rectum.

855 patients with clinicopathologic diagnosis of

ulcerative colitis

23 patients who underwent MDCT and biopsy within 7 days

Exclusion (n = 24)

• Single slice CT was performed

Exclusion (n = 59)

• CT was performed without IV contrast (n = 14)

• CECT was not available for review (n = 3)

• Colectomy or ileo-anal pouch surgery was performed prior to the CECT (n = 42)

Exclusion (n = 633)

• Did not undergo cross-sectional imaging

Exclusion (n = 116)

• Interval between CECT and biopsy > 7 days

Fig. 1. Flow diagram of study patients.

62 B. Patel et al.: MDCT assessment of ulcerative colitis

Clinical severity

The clinical severity of UC for each patient was scored attime of the colonoscopy by a single gastroenterologistusing the non-endoscopic Mayo scoring criteria forassessment of UC activity (Table 1) [10, 21]. Scores couldrange from 0 to 9, with higher scores indicating moresevere disease activity.

MDCT image analysis

Each CECT study was evaluated in consensus by twoabdominal trained radiologists who were blinded to theclinical history, colonscopy findings, and biopsy results.All CECT images were reviewed on a Centricity PACSworkstation (IMPAX, Agfa, GE) and measurementswere done using an electronic ruler. The lower GI tractwas divided into six anatomic segments (rectum, sigmoidcolon, descending colon, transverse colon, ascendingcolon, and cecum). Therefore, a total of 138 segmentswere evaluated (Fig. 2).

Bowel wall thickening was graded as follows: normal(<3 mm, score 0), mild (3–6 mm, score 1), moderate(6–9 mm, score 2), and severe (>9 mm, score 3). Mea-surements of colonic wall thickness were obtained in anon-dependent, well distended segment of bowel to pre-vent false positive measurements due to fecal debris orinadequate distention. Mucosal hyperenhancement, pe-ricolonic stranding, and mural stratification were alsoevaluated and scored as present (score 1) or absent (score0). The presence of submucosal fat was evaluated as aseparate feature and not included in the scoring ofmucosal stratification. Mesenteric hyperemia, defined asengorgement of the mesenteric vessels, was graded as

normal (score 0), mild (score 1), and moderate (score 2).The presence of pericolonic lymph nodes was gradedbased on size: no lymph nodes (score 0), largest lymphnode long axis < 5 mm (score 1) and largest lymph nodelong axis > 5 mm (score 2).

A composite CT severity score (0–10 points) wasestablished by summing all the individual criteria scoresdescribed above.

The colonic segments were evaluated for the presenceof pseudopolyps and submucosal fat. In each patient, thepresacral space was also measured to assess for widening,defined as greater than 15 mm. The presacral space wasdefined as the distance from the posterior wall of therectum to the anterior cortex of the sacrum. In eachpatient, the liver was assessed for CECT features of PSC.In addition, each CECT scan was evaluated for ascites,portal vein thrombosis, intraperitoneal abscesses, andfree intraperitoneal air.

Colonoscopy

A total of 84 segments were evaluated with colonoscopyby multiple gastroenterologists who were blinded to theCECT and histopathologic findings (Fig. 2). Scores wereextracted from the description of each colonoscopy re-port by a single gastroenterologist, who used the Mayoscoring system for lower endoscopy assessment of UCdisease activity [10, 21]. Endoscopy findings were gradedas normal or inactive disease (score 0), mild disease(erythema, decreased vascular pattern, mild friability;score 1), moderate (marked erythema, absent vascularpattern, friability, erosions; score 2), and severe disease(spontaneous bleeding, ulceration; score 3).

Table 1. Mayo scoring system for assessment of ulcerative colitisactivity (without endoscopic criteria)

Stool frequencya

0 = Normal no. of stools for patient1 = 1 to 2 stools more than normal2 = 3 to 4 stools more than normal3 = 5 or more stools more than normal (subscore, 0–3)

Rectal bleedingb

0 = No blood seen1 = Streaks of blood with stool less than half the time2 = Obvious blood with stool most of the time3 = Blood alone passes (subscore, 0–3)

Physician’s global assessmentc

0 = Normal1 = Mild disease2 = Moderate disease3 = Severe disease (subscore, 0–3)

aEach patient serves as his or her own control to establish the degree ofabnormality of the stool frequencybThe daily bleeding score represents the most severe bleeding of the daycThe physician’s global assessment acknowledges the other criteria, thepatient’s daily recollection of abdominal discomfort and general senseof well-being, and other observations, such as physical findings and thepatient’s performance status

23 patients who underwent CECT and biopsy within 7

days

138 segments graded by CECT rectum (n = 23) sigmoid colon (n = 23) descending colon (n = 23) transverse colon (n = 23) ascending colon (n =23) cecum (n = 23)

84 segments graded by lower endoscopy

rectum (n = 23) sigmoid colon (n = 23) descending colon (n = 12) transverse colon (n = 10) ascending colon (n =8) cecum (n = 8)

52 segments graded by histopathology

rectum (n = 16) sigmoid colon (n = 18) descending colon (n = 8) transverse colon (n = 7) ascending colon (n =1) cecum (n = 2)

Fig. 2. Flow diagram of graded segments.

B. Patel et al.: MDCT assessment of ulcerative colitis 63

Histopathologic analysis

A total of 52 segments were biopsied and all specimenswere fixed in formalin and processed for paraffin sec-tions in the routine fashion (Fig. 2). Hematoxylin andeosin-stained slides were reviewed over the course of thestudy by different gastrointestinal pathologists who wereblinded to clinical history, colonoscopic, and CECTfindings. Scores were extracted from the description ofeach pathology report, as normal or inactive colitis(score 0), mild colitis (cryptitis; score 1), moderate colitis(crypt abscesses; score 2), and severe colitis (ulceration;score 3).

Statistical analysis

For each individual colonic segment, the composite CTseverity score as well as the individual CT score for eachfeature were correlated with the corresponding colono-scopic and histopathologic scores using Spearman cor-relation (r). In addition, for each individual colonicsegment, the colonoscopic score was correlated with thecorresponding histopathologic score using Spearmancorrelation (r). Correlation coefficients >0.7, >0.5 to<0.69, >0.3 to <0.49, >0.1 to <0.29, and >0.01 to<0.09 were interpreted as indicators of very strong,substantial, moderate, low, and negligible associations,respectively [11]. A P value of less than 0.05 was con-sidered statistically significant.

For each patient, the highest segmental score forcomposite CT severity, each individual CT score, col-onoscopic, and histopathologic scores were also corre-lated with the clinical severity score. Data were analyzedusing statistical software (SPSS 10.0, Statistical Packagefor the Social Sciences, Chicago, IL). A P value of lessthan 0.05 was considered statistically significant.

Results

Clinical assessment

All 23 patients had positive non-endoscopic Mayo clin-ical scores. The maximum score of 9 was given to nine(39%) patients. The distribution of clinical scores isshown in Fig. 3.

MDCT

All 23 patients had abnormal CECT features involving atleast one colonic segment. Of these 23 patients, seven(30%) had positive findings restricted to the left colon,seven (30%) demonstrated pancolitis, and two (9%) pa-tients had rectal sparing. The segmental distributionbased on CECT findings is shown in Fig. 4. Of the 138segments evaluated, 95 (69%) had an abnormal com-posite CT severity score (greater than zero).

All 23 patients demonstrated bowel wall thickeninginvolving at least one colonic segment. Of 138 evaluatedsegments, 84 (61%) had bowel wall thickening. Mildthickening was seen in 23 colonic segments, withmoderate and severe thickening present in 41 and 20segments, respectively (Figs. 5, 6). Mucosal hyperen-hancement was identified in 17 (74%) patients and 48colonic segments (Figs. 5, 6). Mural stratification waspresent in 16 (70%) patients and 46 colonic segments(Fig. 6). Mesenteric hyperemia was present in 21 (91%)patients and 73 colonic segments (Figs. 5, 6). Mild mes-enteric hyperemia was identified in 46 colonic segmentsand moderate mesenteric hyperemia was seen in 27.Pericolonic stranding was present in 14 (61%) patientsand 30 colonic segments. All 23 patients had pericoloniclymph nodes. Pericolonic lymph nodes <5 mm in longaxis were present 6 (26%) patients and 46 segments, andlymph nodes >5 mm were identified in 17 (74%) patientsand 27 segments. The segmental distribution of thecomposite CT severity score and individual CT featuresis shown in Table 2.

In the 21 patients, who did not demonstrate rectalsparing, the mean presacral space was 10 mm (range 1–19 mm) and five (24%) patients demonstrated wideningof the presacral space (Fig. 7). In one patient, CECTdemonstrated two pseudopolyps, which were confirmedwith endoscopy and histopathology (Fig. 5). On CECT,features of PSC were identified in two patients. One

Distribution of Clinical Severity

1

3

0

3

12

1

3

9

0

2

4

6

8

10

1 2 3 3 5 6 7 8 9

Modified Mayo Score

Num

ber

of P

atie

nts

Fig. 3. Distribution of clinical severity scores.

Distribution of Colonic Involvement on CECT21 22 21

15

107

0

5

10

15

20

25

R SC DC TC AsC C

Segment

Num

ber

of P

atie

nts

Fig. 4. Segmental distribution based on CECT. R rectum,SC sigmoid colon, DC descending colon, TC transverse co-lon, AsC ascending colon, C cecum.

64 B. Patel et al.: MDCT assessment of ulcerative colitis

patient had ascites and one demonstrated portal veinthrombosis on CECT.

Optical colonoscopy

Positive colonoscopic findings were present in 22 (96%)patients. Of the 84 segments evaluated with colonoscopy,56 (67%) segments had a score greater than zero. Mild

disease was present in 15 (18%) segments, with moderateand severe disease present in 24 (29%) and 17 (20%)segments, respectively. The distribution of segmentalinvolvement assessed by colonoscopy is shown inTable 2. Colonoscopy demonstrated pseudopolyps infour (17%) patients. In one patient, two pseudopolypswere identified which were also seen on CECT (Fig. 5).One pseudopolyp was identified in each of the remainingthree patients, none of which were seen on CECT.

Histopathology

Positive histopathology findings were present in 22 (96%)patients. Of 52 segments evaluated with histopathology,51 (98%) segments had a score greater than zero. Milddisease was present in three segments, with moderate andsevere disease present in 44 and four segments, respec-tively.

Total colectomy was eventually performed in threepatients due to severe disease, which was confirmed onpathology specimens. The mean time interval betweenbiopsy and colectomy was 11 days (range of 5–16 days).

Correlation between clinical assessment, CECT,colonoscopy, and histopathology

Bowel wall thickening, mucosal hyperenhancement,mural stratification, mesenteric hyperemia, and perico-lonic lymph nodes each individually demonstrated amoderately positive association with colonoscopicseverity (P < 0.05). Pericolonic stranding demonstrateda weak positive association with colonoscopic severity.The composite CT severity score had the greatest positiveassociation with colonoscopic severity (P = 0.002). TheSpearman correlation values between CECT and colon-oscopy are shown in Fig. 8.

The composite CT severity score had a weak positiveassociation with clinical severity while bowel wall thick-ening, mucosal hyperenhancement, and mural stratifica-tion each individually showed a moderate positiveassociation with clinical severity. Optical colonoscopy

Fig. 5. Axial (A) and coronal (B) contrast-enhanced CTimages obtained during the portovenous phase in a 38-year-old female demonstrate two enhancing mucosal lesions in therectum and sigmoid colon (arrows). Mucosal hyperenhance-ment (black arrowhead) along with circumferential and sym-metric bowel wall thickening (white arrowheads) is present.Mesenteric hyperemia (black arrows) is present in the peric-olonic fat. C Colonoscopy image of the sigmoid colon con-firms the polypoid mucosal lesion (arrows), which washistologically proven to be a inflammatory pseudopolyp.(Sigmoid colon segmental scores were as follows: compositeseverity, 8; colonoscopic, 3; histopathologic, 2; clinicalseverity, 8.)

b

B. Patel et al.: MDCT assessment of ulcerative colitis 65

had the greatest positive association with clinical sever-ity. The Spearman correlation values between CECT andclinical severity are shown in Fig. 9.

Only bowel wall thickening, as an individual CECTfeature, showed a weak positive (r = 0.35, P < 0.05)association with histopathologic severity. Similarly, nocorrelation between colonoscopy and histopathologywas demonstrated.

Discussion

The ability of MDCT to image the bowel wall and ser-osa, and thus evaluate transluminal extent of disease,makes this imaging modality a powerful diagnostic toolin the detection and characterization of many inflam-matory conditions of the colon [9]. For instance, in casesof colonic Crohn disease, CT has been shown to affectdisease management in 28% of cases [12]. Similarly, insevere cases of UC, where colonoscopy is contraindi-cated due to increased risk of perforation or exacerbationof disease activity [7, 13], or in situations where completeendoscopic evaluation of the colon is not possible (5–20% of cases) [5], CT is readily used as an alternativediagnostic tool. However, a systematic approach thatuses CT in assessing UC disease severity has not beenpresented in the literature.

Historically, CT has had a limited role as a primaryimaging tool in assessing patients with UC. In our study,only 26% of patients with UC underwent CT imaging.Studies in the remote literature do not recommend CTimaging as a primary means of diagnosing UC due to thelow diagnostic sensitivity for early disease [14]. The earlystages of UC are manifested colonoscopically by agranular pattern due to edema and hyperemia whichhave been described to be beneath the spatial resolutionof CT [14–17]. However, these studies were performedusing single slice scanners [15, 16]. In contradistinction,our study, where 18% of segments evaluated by colon-oscopy had mild or early disease, MDCT demonstratedpositive correlation with colonoscopic severity.

Despite UC being a mucosal disease, bowel wallthickening is a common CT feature [8, 14]. The active

Fig. 6. Axial (A–C) contrast-enhanced CT images obtainedduring the portal venous phase in a 40-year-old male withbloody diarrhea demonstrate circumferential and symmetricbowel wall thickening extending proximally from the rectum.There is mural stratification with enhancement of the innermucosa (solid arrows) and outer muscularis propria (dashedarrow). The lines are separated by the edematous submu-cosa (asterisks). Mesenteric hyperemia is seen in the peric-olonic fat (arrowheads). C CECT also demonstrates exclusiveinvolvement of the left colon. D The patient subsequentlyunderwent a total colectomy which demonstrated erythema,friability, and inflammation involving the left colon. (Sigmoidcolon segmental scores were as follows: composite severity,9; colonoscopic, 3; histopathologic, 2; clinical severity, 9.)

b

66 B. Patel et al.: MDCT assessment of ulcerative colitis

inflammatory phase of UC is characterized by neutrophilinfiltration of the lamina propria, associated with edema,congestion, hemorrhage, and surface erosion and ulcer-ation [24]. Colonic wall thickening was present in all 23patients and, as an independent CT feature of UC,demonstrated to have positive association with colono-scopic, clinical, and histopathologic severity. To the bestof our knowledge, there are no studies in the literaturethat evaluate the correlation between bowel wall thick-ening and disease severity in UC. A review by Maccioniet al. [22], however, illustrates how magnetic resonanceimaging (MRI) is useful to detect morphologic changesand disease activity of UC. MRI can be a reliable diag-nostic tool for UC, because it is useful for integratingclinical and endoscopic data [22, 23]. Most typical find-ings of UC, such as bowel wall thickening, mural strat-ification and several complications can be detected withMRI [22].

In general, the normal colonic wall thickness shouldbe not more than 3 mm, and is usually 1–2 mm whenwell distended [19]. In a study by Philpotts et al. [18],bowel wall thickening in UC (7.8 ± 1.9 mm) was de-scribed to be less than that in Crohn disease (11.0 ± 5.1).In our study, nearly half (49%) of segments that dem-onstrated bowel wall thickening had a thickness between6 and 9 mm. In UC, wall thickening is circumferentialand symmetric with the rectum nearly always demon-strating inflammatory changes, as was seen in our series.In the absence of treatment with steroids or 5-amino-salicyclic acid enemas, rectal sparing can be seen inapproximately 4% of cases [6, 8].

Mucosal hyperenhancement is best depicted with ra-pid-bolus, thin section CECT scanning [20]. This CTfeature indicates inflamed mucosa, usually seen withacute inflammation, reflecting a hyperemic and hyper-vascular state [14]. Although a described feature in UC,there are no studies in the literature that evaluate thecorrelation of mucosal hyperenhancement with diseaseseverity [8]. In our series, mucosal hyperenhancementdemonstrated a positive association with clinical severity.As an independent CECT feature, mucosal hyperen-hancement had the highest positive association with

colonoscopic severity, explained by the excellent colonicmucosal visualization with optical colonoscopy.

During the active inflammatory phase of acute orsubacute UC, the submucosa becomes thickened due toedema, which contributes to mural heterogeneity [14]. Inchronic UC, the muscularis mucosa becomes markedlyhypertrophied, associated with widening and fat depo-sition within the submucosa [14]. There are no studies inthe literature evaluating the prevalence of mural heter-ogeneity solely in cases of acute or subacute UC. In thestudy by Philpotts et al. [18], 70% of patients with UCdemonstrated mural heterogeneity, with the majority(61%) due to submucosal fat deposition. In our series,mural heterogeneity related to fat deposition was notscored as mural stratification to use this CT feature toassess for acute and subacute disease severity. Muralstratification was identified in 70% of patients anddemonstrated a positive association with optical colon-oscopy. Of all the individual CT features, mural strati-fication had the highest positive correlation with clinicalseverity.

Although each CT feature individually had a positiveassociation with optical colonoscopy severity, whencombined, the CT severity score had the highest positiveassociation. Conversely, the correlation between the CTseverity score and clinical severity was lower comparedto the individual CT features. This emphasizes the valueof evaluating all CECT features both independently andtogether when assessing severity.

Colonoscopy permits visualization of colonic mucosaand allows for tissue sampling. In our series, opticalcolonoscopy had a strong association with clinicalseverity. This correlation was greater than both thecombined CT severity and individual CT feature scores.In addition, optical colonoscopy demonstrated a greatersensitivity than CT for detecting pseudopolyps, whichare mucosal based lesions. With the MDCT techniqueand patient preparation used in this series, small pseud-opolyps could be obscured by collapsed bowel and highdensity intraluminal contents. Optical colonoscopy,however, does also have limitations as it cannot evaluatesubmucosal, mesenteric, and extraintestinal involvement.

Table 2. Distribution of segmental involvement as assessed by CECT and colonoscopy

# of patients Percentage of segments involved (%) R SC DC TC AsC C

CECTComposite CT Severity 23 (100%) 69 19 22 21 15 10 7Wall thickening 23 (100%) 61 19 20 20 14 6 4Mucosal hyperenhancement 17 (74%) 35 11 15 8 4 6 4Mural stratification 16 (70%) 33 10 14 7 3 7 5Mesenteric hyperemia 21 (91%) 53 14 17 13 9 11 9Pericolonic stranding 14 (61%) 22 7 12 5 1 3 2Lymph nodes 23 (100%) 53 15 18 10 9 8 10

Colonoscopy 22 (96%) 67 19 20 9 5 2 1

R rectum, SC sigmoid colon, DC descending colon, TC transverse colon, AsC ascending colon, C cecum

B. Patel et al.: MDCT assessment of ulcerative colitis 67

Evaluation of the mucosa with colonoscopy alone canunderestimate the transmural extent and activity of dis-ease [5].

CT has the added advantage of assessing for extra-intestinal involvement and complications of UC, asdemonstrated in our study. Rectal luminal narrowingand widening of the presacral space due to muralthickening and proliferation of perirectal fat are hall-marks of chronic disease [14]. This extraintestinal featureis readily identified with CT, where the perirectal fat hasbeen described to have a slightly increased attenuation(10–20 HU) relative to normal mesenteric fat (-55 to-75 HU) and may contain nodular and streaky areas ofsoft-tissue attenuation and enlarged perirectal lymphnodes [8, 14]. Widening of the presacral space waspresent in 22% of patients in our study.

In UC, repeated bouts of inflammation lead tochronic mucosal injury. Superimposed inflammatoryactivity represents chronic active colitis, and the degreeof activity can be graded. Neither colonoscopic norcomposite CT severity demonstrated a statistically sig-nificant association with histopathologic severity. Fur-thermore, among the individual CECT features, onlybowel wall thickening demonstrated a weak positiveassociation with histopathologic severity.

One limitation of this study is that the normalthickness of the colonic wall varies greatly based on thedegree of distension [19]. If the colon is collapsed, filledwith fecal contents, fluid or redundant, the true thicknessmay be difficult to optimally obtain. In our study,whenever possible, wall thickness was measured in seg-ments of colon distended with gas to obtain the most

accurate measurement. Another limitation to consider isthe 7-day interval (mean 2.4 days) between the CECTand colonoscopy with mucosal biopsy. Ideally, theCECT and colonoscopy would be obtained on the sameday to reduce possible differences in disease severity,related to interval treatment or progression of disease.

As this study was performed in a retrospective singlecenter manner, there are inherent limitations with regardto lack of randomization and blinding when selectingpatients from the computerized lower endoscopy andpathology databases, introducing possible selection bias.Of the 855 patients diagnosed with UC, only 198underwent cross-sectional imaging with MDCT. Theseselected patients may not necessarily represent the truedemographic population of those with UC, as patientswho undergo CT tend to have a more severe flare ofsymptoms or potential complications.

Being retrospective, there was no control in how theendoscopic sampling was obtained. As 20 (87%) of thepatients presented with an acute flare of UC, it is possiblethat the most severe appearing mucosa was targeted forsampling, which may not be completely representative of

Correlation of CECT with Colonoscopy

0.50.57 0.54 0.53

0.450.5

0.62

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

BWT Muc.H MS Str. LN Total

CECT Criteria

Spea

rman

cor

rela

tion

(r)

)

Mus.H

Fig. 8. Spearman correlation between CECT and colonos-copy severity. BWT bowel wall thickening, Muc. H mucosalhyperenhancement, MS mural stratification, Mes. H hyper-emia, Str. pericolonic stranding, LN pericolonic lymph node,Total cumulative CT score (P < 0.05).Fig. 7. Transverse CT image in a 45-year-old woman with

ulcerative colitis shows perirectal fat proliferation resulting inwidening of the presacral space to 18 mm (straight doubleheaded arrow). The perirectal fat is higher than normal inattenuation and contains nodular and streaky areas ofincreased attenuation (arrows). The rectal wall is thickenedand demonstrates luminal narrowing.

Correlation with Clinical Severity

0.45

0.58 0.57

0.750.68

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Total BWT Muc.H MS Opt. Col.

Spea

rman

cor

rela

tion

(r)

Fig. 9. Spearman correlation clinical severity. Total- Cumu-lative CT score. BWT bowel wall thickening, Muc. H mucosalhyperenhancement, MS mural stratification, Opt. Col. opticalcolonoscopy (P < 0.05).

68 B. Patel et al.: MDCT assessment of ulcerative colitis

the disease severity integrated over an entire colonicsegment. In distinction, with sampling performed in pa-tients with long standing disease who are undergoingsurveillance for dysplasia (n = 3), the mucosal biopsiesare typically random. Although this limitation exists,performing random biopsies in patients with UC exac-erbations tends not to occur in real clinical practice.Furthermore, as a retrospective study, the possibility ofconfounding causes affecting the frequency of occurrenceof certain MDCT features in individuals selected cannotbe entirely excluded. Finally, our small sample size of 23patients can potentially overestimate the magnitude ofcorrelation producing false positive results. We tried tolimit this statistical bias by introducing colonic segments,thereby increasing the number of evaluated samples.

In our study, there were less colonic segments evalu-ated by histopathology (n = 52) and colonoscopy(n = 84) compared to the 138 segments evaluated byMDCT. This difference is attributed to incomplete col-onoscopies and the fact that not all segments seen duringcolonoscopy were biopsied. For a given modality,spearman correlation analysis assessed each segmentindividually and independently, comparing the scoreonly against the corresponding segment for anothermodality. As a result, more correlations could be madebetween MDCT and colonoscopy than with histopa-thology. Even though spearman correlation takes samplesizes into account, the lower number of segments evalu-ated by colonoscopy and especially histopathology, maybe considered a limitation affecting the results.

In summary, CECT and colonoscopy each has dis-tinct advantages and limitations when assessing theseverity of UC, and can be used together to both rein-force and supplement information. CECT, colonoscopy,and clinical assessment demonstrate positive associationwith each other and, therefore, have a complementaryrole when evaluating patients with UC. In cases wherecolonoscopy is contraindicated or in critically ill patients,MDCT should be readily used in conjunction with clin-ical assessment to determine disease severity. Further-more, in cases where a discrepancy between colonoscopyand clinical findings is present, MDCT may be consid-ered as a problem-solving tool.

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