Gut, 1992,33,65-70

Distribution of collagenous colitis: utility of flexiblesigmoidoscopy

M Tanaka, G Mazzoleni, R H Riddell

AbstractWe investigated the distribution of thecollagen band in 33 patients with collagenouscolitis to estimate the likelihood of thedisease being diagnosed in biopsy specimensfrom the left side of the colon, such as thoseobtained using flexible sigmoidoscopy. To beincluded in this study patients had a sub-epithelial collagen band -10 [lm, an increasein chronic inflammatory cells in the samespecimen, and diarrhoea for which there wasno other apparent cause. In 17 patients under-going full colonoscopy with a thickenedcollagen band, collagenous colitis was fre-quently patchy, even though overall thethickened collagen band was almost equallydistributed throughout the colon. Rectalbiopsy specimens showed a normal collagenband in 73% of patients, while a thickenedcollagen band was found in 82% of patients inat least one specimen from the left side of thecolon. Three patients had a thickened collagenband only in the caecum. In three of eightrectal biopsy specimens with a normal collagenband there was no mucosal inflammation toraise the possibility of proximal disease,although all but one specimen with a normalcollagen band from the sigmoid and descend-ing colon were inflamed. Rectal biopsy alone istherefore a relatively poor method of makingthe diagnosis. Flexible sigmoidoscopy withmultiple biopsy specimens from several sites isa reasonable initial investigation but not suf-ficient to exclude collagenous colitis whenbased on the presence of a thickened collagenband alone. Should left sided biopsy speci-mens show a normal collagen band but aninflamed mucosa, total colonscopy withmultiple specimens including the caecum maybe required to establish the diagnosis.

Department ofPathology, McMasterUniversity MedicalCentre, Hamilton,Ontario, CanadaM TanakaG MazzoleniR H RiddellCorrespondence to:Dr Robert H Riddell,Department of Pathology,McMaster University MedicalCentre, 1200 Main StreetWest, Hamilton, Ontario,L8N 3Z5 Canada.Accepted for publication23 April 1991

Collagenous colitis is an uncommon condition ofunknown cause affecting the large bowel, withcharacteristic histological changes of a thickenedeosinophilic and hypocellular subepithelialcollagen band and an increase in inflammatorycells in the lamina propria, primarily plasmacells, often with an increase in intraepitheliallymphocytes, and often intraepithelial andlamina propria, neutrophils or eosinophils.'-'Colorectal biopsy specimens are required fordiagnosis from patients suspected of havingcollagenous colitis, because there is usually noradiographic or endoscopic abnormality.68 1416Several reports have suggested that the diseasemay be focal, but its precise distribution remainsunclear.25'0'5 ' It is also unclear whether col-lagenous colitis is accompanied by diffuse in-flammation throughout the large bowel even in

patients without a diffuse diagnostic collagenband, in which case flexible sigmoidoscopicbiopsy specimens could reasonably excludeproximal disease.The purpose of this study was to investigate

the distribution of the disease, and to estimatethe value and the limitations of proctoscopic orflexible sigmoidoscopic biopsy.

MethodsPatients were identified by review of the surgicalpathology files of McMaster University MedicalCentre and the record of weekly gastrointestinalbiopsy conferences from 1985 to early in 1990.Clinical records were also reviewed to excludepatients with other conditions which may causediarrhoea, such as radiation, infective andpseudomembranous colitis, and inflammatorybowel disease. Two patients who also had coeliacdisease which had not fully responded to treat-ment were included in this study.The thickness of the subepithelial collagen

band was measured at two points in well orientedparts of the biopsy specimens at the thickestpoints of each colorectal specimen. Eachmeasurement was carried out by two patholo-gists independently, using haematoxylin andeosin slides (and trichrome stain if needed) and acalibrated eye piece graticule. When there werecapillaries with a thickened wall within thecollagen band, band thickness was measured atthe part not affected by the capillaries (Fig 1).Interobserver variation was almost exclusivelydue to different points of the specimens beingmeasured rather than to techniques of measure-ment. Agreement was obtained after verifyingwhich points were appropriate for measurement.The mean thickness of the collagen band wascalculated from both readings at each site in thelarge bowel, which was divided into caecum,ascending colon to hepatic flexure, transversecolon to splenic flexure, descending colon,sigmoid colon, and rectum. Multiple specimens(up to four) taken from the same site wereanalysed collectively as a single specimen usinga mean collagen band thickness which wasevaluated as an average of all specimens at thissite. To compare flexible sigmoidoscopic speci-mens with full colonoscopic specimens, the largebowel was divided into the left colorectumincluding the rectum to the descending colonand the proximal colon including the splenicflexure to the caecum.The normal collagen band is less than 7 itm

thick,58 1118 19 and in reported cases of collagen-ous colitis the collagen band is thicker than 10jim and accompanied by mucosal inflamma-tion.258 14 1619 On the basis of these data, we useda mean thickness of 10 jtm or more and an

65

Tanaka, Mazzoleni, Riddell

Figure 1: The subepithelial collagen band between the arrows is 7 urm (upper limit ofnormal) (A), 10 urm (B), and 20 rm (C).(D) When capillaries (arrow) existed within the collagen band the thickness ofthe collagen band was measured at the part withoutthe direct effect (between the arrows). (Haematoxylin & eosin, original magnification x 460).

increase in chronic inflammatory cells in thesame specimen as the diagnostic criteria forcollagenous colitis.

DISTRIBUTION OF COLLAGENOUS COLITISTo determine the distribution of the disease,specimens obtained at full colonoscopy wereexamined retrospectively in patients with the

disease as defined above. Full colonoscopicexaminations in which at least one specimen hada mean collagen band thickness of 10 Fm ormore and in which biopsy specimens were takenfrom both the proximal and the left colorectumwere selected. The proportion of positive speci-mens (mean thickness .10 utm) at each siteoverall was also investigated.

Fisher's exact probability test was used for

66

Distribution ofcollagenous colitis: utility offlexible sigmoidoscopy

Figure 2: Sample ofincreased (A) and normal (B) cellularity in the lamina propria(Haematoxylin & oesin, original magnification x 180).

statistical analysis of independent variables ofpositive and negative biopsy specimens betweendifferent sites.

PROBABILITY OF DIAGNOSING COLLAGENOUSCOLITISUsing the same study group as that selectedabove, colonoscopic specimens were examinedto estimate the chance of making the correctdiagnosis in specimens sequentially by site. Theproportion of the cumulative positive specimens(mean thickness -10 ,um) to each site wasinvestigated.

MUCOSAL INFLAMMATION IN LEFT SIDEDSPECIMENS WITH A NORMAL COLLAGEN BAND

Using the same study group specimens with a

mean thickness of< 10 tLm in the left colorectumwere examined to determine whether cellularityin the lamina propria was increased or normal(Fig 2). In left sided specimens without a thick-ened collagen band, and in which the diagnosisof collagenous colitis could not therefore be

made, the number of intraepithelial lymphocytes(number/100 epithelial cells) were countedto determine whether they were present inincreased numbers in specimens with and with-out an increase in inflammatory cells, and there-fore whether they would be a better predictor ofthe presence of collagenous colitis elsewhere.

PROBABILITY OF DIAGNOSING COLLAGENOUSCOLITIS AT INITIAL ENDOSCOPYTo estimate the probability ofmaking the correctdiagnosis on the initial endoscopy, specimensfrom the initial endoscopy (proctosigmoido-scopy or full colonoscopy) were examined. Thetest selected depends on the differing practicesfor endoscopy and biopsy of several gastro-enterologists and trainees. The cumulative pro-portion of positive biopsy specimens (meanthickness -10 ,tm) to each site was determined.

ResultsThirty three patients were identified withcollagenous colitis defined by diarrhoea,minimal or no endoscopic abnormality, and amean collagen band thickness of 10 [tm or morewith an increase in chronic inflammatory cells.Altogether 60 large bowel endoscopies werecarried out. This study group consisted of 30females and three males, mean (SD) age 610(16- 1) years, range 2-87 years. Two patients hadcoeliac disease which had failed to respond fullyto a gluten free diet.

DISTRIBUTION OF THE THICKENED COLLAGENBAND IN 17 PATIENTS UNDERGOING FULLCOLONOSCOPY WITH MULTIPLE BIOPSY SPECIMENSINCLUDING AT LEAST ONE POSITIVE SPECIMENThe proportion of positive specimens at each siteis given in Table I. The number of biopsyspecimens taken at each site varied from one tothree, with a mean (SD) number of 1-4 (0 7).The proportion of patients with positive speci-mens was significantly less for the rectum (27%)than for other sites (60%-83%) whether com-pared with other sites individually (p<005) orcollectively (p<001). In five of 17 patients inwhom only one specimen was positive, threewere taken from the caecum, one from thedescending colon, and one from the rectum. Inaddition, the thickness of the collagen band wasnot uniform among the specimens even at thesame site in several patients.

PROBABILITY OF DIAGNOSING COLLAGENOUSCOLITIS IN 17 PATIENTS UNDERGOING FULLCOLONOSCOPYThe cumulative percentage ofpositive sequentialspecimens by site in 17 patients undergoing fullcolonoscopy with positive specimens is given inTable II. Had proctoscopy only been carried out,the yield from rectal specimens alone would haveremained low, but had flexible sigmoidoscopybeen carried out, this would have increased theyield to 82% of patients. In three of 17 patientsthe diagnosis was only apparent in the caecalbiopsy specimen.

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TABLE I Proportion (and percentage) ofbiopsy specimens with a mean collagen band thicknessof-10-Im at each site in 17 patients undergoingfull colonoscopy

Transverse Ascendingcolon to colon

Sigmoid Descending splenic hepaticRectum colon colon flexure flexure Caecum

Proportion(%) 3/11 (27) 8/11 (73) 8/11 (73) 9/11 (82) 6/10 (60) 10/12 (83)

p<0.05p<005

p<O.005p<0.05

Fischer's exact probability test.

MUCOSAL INFLAMMATION AND NUMBER OFINTRAEPITHELIAL LYMPHOCYTES IN BIOPSYSPECIMENS FROM THE LEFT SIDE WITH A MEANTHICKNESS OF < 10 [LM FROM NINE OF 17PATIENTS UNDERGOING FULL COLONOSCOPYThe number of biopsy specimens with a meanthickness of < 10 [im in nine of these 17 patientswas eight in the rectum, three in the sigmoidcolon, and three in the descending colon,respectively (Table III). In the rectum, five ofeight specimens with a mean thickness of <10,im showed inflammation of the lamina propria,primarily plasma cells. The number of intra-epithelial lymphocytes correlated closely with anincrease in inflammation in the lamina propria.In three specimens in which there was noincrease in cellularity of the lamina propria therewere -6 intraepithelial lymphocytes per 100epithelial cells (normal), while these threepatients also had specimens with a mean thick-ness of -10 [tm from the sigmoid colon. In thesigmoid and descending colon all specimensexcept one with a mean thickness of <10 [imshowed inflammation of the lamina propria. All17 patients undergoing full colonoscopy had atleast one specimen from the left side with either athickened collagen band or mucosal inflamma-tion.

PROBABILITY OF DIAGNOSING COLLAGENOUSCOLITIS IN 33 INITIAL ENDOSCOPIESTwenty three of 33 initial endoscopies wereproctoscopy or flexible sigmoidoscopy and leftsided biopsies alone; the remainder were fullcolonoscopy. The cumulative percentage of thepositive specimens (mean thickness -10 ,um) toeach site at initial endoscopy is given in Table IV.From one to four biopsy specimens were taken ateach site, with a mean (SD) number of 1-6 (0-8).A diagnosis of collagenous colitis was made in78% ofpatients using the specimens from the leftcolorectum only, and in 85% using the speci-mens from the whole large bowel. Five patientsin whom the diagnosis was not made had onlyone biopsy (three rectum, two sigmoid colon). In

TABLE~II Cumulative proportion ofbiopsy specimens with a mean collagen band thickness of>10 [sm in 17 patients undergoingfull colonoscopy

Transverse Ascendingcolon to colon

Sigmoid Descending splenic hepaticRectum colon colon flexure flexure Caecum

Proportion (%) 3/11 (27) 10/14 (71) 14/17 (82) 14/17 (82) 14/17 (82) 17/17 (100)

one of these five patients collagenous colitis wasfound in the proximal colon only at subsequentcolonoscopy and in four it was subsequentlyfound either in the left colorectum or bothproximally and distally.

DiscussionSome reports have suggested that in collagenouscolitis a thickened collagen band tends to bemore prominent in the proximal colon andmay sometimes be absent in the distal colo-rectum.8 10141719 We confirm that this is indeedthe case in this series and that the rectum wassignificantly less affected than other sitesindividually (p<005) or collectively (p<001).In 17 patients undergoing full colonoscopy,rectal biopsy specimens showed no thickening ofthe collagen band in eight of 11 patients in whomsuch specimens were taken, whereas the sigmoidand descending colon were involved in 73%,respectively. Between the sigmoid colon and thecaecum no segment was affected more frequentlythan another. In five of the 17 patients only onesite was positive. In addition, the thickness ofthecollagen band was not uniform among specimenseven at the same site in several patients; forexample, in one patient three caecal specimenshad a maximal thickness of 9, 12, and 19 Itm,respectively. The distribution of the collagenband in collagenous colitis is therefore oftenfocal. This implies that in some patients withfocal thickening the likelihood of making thediagnosis is related to the number of specimenstaken. In serial colonoscopies with biopsy speci-mens, care must also be taken in interpreting thepresence or absence of collagenous colitis interms of the natural history - for example,development, resolution - as this may simplyreflect sampling error.The cumulative percentage of full colono-

scopic examinations with a thickened collagenband in left sided large bowel specimensindicates a detection rate of collagenous colitis of27% (3/11) for the rectum, 71% (10/14) for thesigmoid colon, and 82% (14/17) for the descend-ing colon. These results imply that biopsieslimited to the rectum and to the rectosigmoidonly would have missed 73% and 29% of thepatients with the disease, respectively, and thateven when the descending colon was included inthe distal biopsies, 18% of those with the diseasewould have remained undetected. Full and poss-ibly multiple colonoscopies may therefore berequired to make the diagnosis in some patients.

In 17 patients undergoing full colonoscopythree of eight rectal biopsy specimens with amean collagen band thickness of < 10 ,umshowed no increase in either cellularity of thelamina propria or intraerithelial lymphocytes,' 20although all specimens except one with a meanthickness of <10 im from the sigmoid anddescending colon showed an excess of plasmacells in the lamina propria. This implies that therectal biopsy site is least likely to be positive,although in one ofour patients it was the only siteand therefore cannot be excluded from biopsy.However, biopsies in which the degree of inflam-mation in both the sigmoid and descending colonare normal are unlikely to be associated with

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Distribution ofcollagenous colitis: utility offlexible sigmoidoscopy 69

TABLE III Lamina propria inflammation (LPI) and numberofintraepithelial lymphocytes (NIELIIOO epithelial cells inleft sided biopsy specimens with a mean thickness ofcollagenband <10 pm (each line is a different patient)

Rectum Sigmoid colon Descending colon

LPI NIEL LPI NIEL LPI NIEL

+ 22 + 25 + 34+ 25 + 24 + 21+ 20 NB P+ 12 NB NB+ 10 P NB- 6 P P- 4 P P- 5 P NB

P + 14 - 4

+=increased; -=normal; P=positive biopsy with a meanthickness of collagen band 210 pm; NB=no biopsy was takenfrom this site.

collagenous colitis elsewhere in the large boweland may therefore be useful for screening pur-poses.

In one study the number of intraepitheliallymphocytes was found to be (mean (SD)) 24-6(3 0) per 100 epithelial cells in cases with 'micro-scopic colitis." On the basis of this figure, amongour 17 patients three patients showing left sidedspecimens with a mean thickness of <10 ,umfulfilled this criterion. However, this correlatedwith inflammation of the lamina propria and wasnot a useful independent parameter for suspicionof collagenous colitis. Furthermore, an increasein intraepithelial lymphocytes is not specific forcollagenous colitis or microscopic colitis, whichis found in some patients with a similar clinicalsyndrome; it may also be seen in ulcerativecolitis, Crohn's disease, coeliac disease and evenin asymptomatic patients.'The probabilities of making the correct diag-

nosis of collagenous colitis in this series at theinitial endoscopy was 85% in 33 patients. In theremaining five patients a thickened collagenband was not detected at initial endoscopypresumably because affected areas in that part ofthe bowel were not sampled, because disease wasnot present in that part of the bowel, or conceiv-ably because disease developed after the initialendoscopy. A high proportion (55%) of rectalbiopsy specimens were positive at the initialendoscopy compared with 27% in the 17 patientsundergoing full colonoscopy. This false higherproportion was due to a selection bias: in most ofthese patients only rectal biopsy specimens weretaken; indeed there was no great differencebetween the 10 patients undergoing full colono-scopy as initial endoscopy and the 17 patientsundergoing full colonoscopy. Another potentialsource of bias is that our series clearly consistsonly of patients diagnosed as having the disease;

TABLE IV Cumulative proportion ofinitial endoscopic biopsy specimens with a mean collagenband thickness of210 pm (23 flexible sigmoidoscopies and 10 full colonoscopies)

Transverse Ascendingcolon to colon

Proportion Sigmoid Descending splenic hepatic(%) Rectum colon colon flexure flexure Caecum

Flexiblesigmoidoscopy 10/14(71) 17/22 (77) 18/23 (78)

Full colonoscopy 1/6 (17) 4/7 (57) 7/9 (78) 7/9 (78) 7/9 (78) 10/10 (100)Total 11/20 (55) 21/29 (72) 25/32 (78) 25/32 (78) 25/32 (78) 28/33 (85)

patients with collagenous colitis but withunremarkable rectal biopsy specimens alonemight have been excluded from the studyaltogether. Such patients may, for instance, bemanaged as ifthey had irritable bowel syndrome.

Being retrospective, the study is subject tobias. While a prospective study with a standard-ised number of biopsy specimens and biopsysites may have been preferable, practically this isdifficult to achieve in a unit with many gastro-enterologist, fellows, and residents carrying outcolonoscopy in patients with an uncommondisease whose only presenting symptom isdiarrhoea, in whom endoscopy is grossly normaland over a five year period. The retrospectivestudy provides an indication of what actuallyhappens in a gastrointestinal teaching unit, andis therefore much more likely to be representa-tive of current clinical practice than a formalisedprospective study.

In this series rectal biopsy alone was leastreliable for making the diagnosis, although insome patients it may have been the only site ofthe disease. Flexible sigmoidoscopy withmultiple biopsies including the rectum, sigmoid,and descending colon is effective to detect butnot sufficient to exclude collagenous colitis whenbased on the presence of a thickened collagenband alone. But if entirely normal quantitativelyregarding inflammation (primarily plasma cells)in these three sites, then collagenous colitisis unlikely to be found elsewhere. Flexiblesigmoidoscopy with multiple biopsies fromseveral sites is a reasonable initial investigationin patients suspected clinically of havingcollagenous colitis. Should these left sided largebowel biopsy specimens show a collagen band ofnormal thickness but an inflamed mucosa, totalcolonoscopy with multiple biopsies from everysite including the caecum may be required toestablish the diagnosis if there is a persistentclinical suspicion of this disease. An increase inintraepithelial lymphocytes was not found in theabsence ofan increased inflammatory infiltrate inthe lamina propria and was therefore of littleadditional value.

We thank Mrs Janice Butera and Mrs Barb Lahie for assistance inmanuscript preparation.

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