Distribution of collagenous colitis : utility of flexible

We investigated the distribution of the collagen band in 33 patients with collagenous colitis to estimate the likelihood of the disease being diagnosed in biopsy specimens from the left side of the colon, such as those obtained using flexible sigmoidoscopy. To be included in this study patients had a subepithelial collagen band -10 [lm, an increase in chronic inflammatory cells in the same specimen, and diarrhoea for which there was no other apparent cause. In 17 patients undergoing full colonoscopy with a thickened collagen band, collagenous colitis was frequently patchy, even though overall the thickened collagen band was almost equally distributed throughout the colon. Rectal biopsy specimens showed a normal collagen band in 73% of patients, while a thickened collagen band was found in 82% of patients in at least one specimen from the left side of the colon. Three patients had a thickened collagen band only in the caecum. In three of eight rectal biopsy specimens with a normal collagen band there was no mucosal inflammation to raise the possibility of proximal disease, although all but one specimen with a normal collagen band from the sigmoid and descending colon were inflamed. Rectal biopsy alone is therefore a relatively poor method of making the diagnosis. Flexible sigmoidoscopy with multiple biopsy specimens from several sites is a reasonable initial investigation but not sufficient to exclude collagenous colitis when based on the presence of a thickened collagen band alone. Should left sided biopsy specimens show a normal collagen band but an inflamed mucosa, total colonscopy with multiple specimens including the caecum may be required to establish the diagnosis. Department of Pathology, McMaster University Medical Centre, Hamilton, Ontario, Canada M Tanaka G Mazzoleni R H Riddell Correspondence to: Dr Robert H Riddell, Department of Pathology, McMaster University Medical Centre, 1200 Main Street West, Hamilton, Ontario, L8N 3Z5 Canada. Accepted for publication 23 April 1991 Collagenous colitis is an uncommon condition of unknown cause affecting the large bowel, with characteristic histological changes of a thickened eosinophilic and hypocellular subepithelial collagen band and an increase in inflammatory cells in the lamina propria, primarily plasma cells, often with an increase in intraepithelial lymphocytes, and often intraepithelial and lamina propria, neutrophils or eosinophils.'-' Colorectal biopsy specimens are required for diagnosis from patients suspected of having collagenous colitis, because there is usually no radiographic or endoscopic abnormality.68 1416 Several reports have suggested that the disease may be focal, but its precise distribution remains unclear.25'0'5 ' It is also unclear whether collagenous colitis is accompanied by diffuse inflammation throughout the large bowel even in patients without a diffuse diagnostic collagen band, in which case flexible sigmoidoscopic biopsy specimens could reasonably exclude proximal disease. The purpose of this study was to investigate the distribution of the disease, and to estimate the value and the limitations of proctoscopic or flexible sigmoidoscopic biopsy. Methods Patients were identified by review of the surgical pathology files of McMaster University Medical Centre and the record of weekly gastrointestinal biopsy conferences from 1985 to early in 1990. Clinical records were also reviewed to exclude patients with other conditions which may cause diarrhoea, such as radiation, infective and pseudomembranous colitis, and inflammatory bowel disease. Two patients who also had coeliac disease which had not fully responded to treatment were included in this study. The thickness of the subepithelial collagen band was measured at two points in well oriented parts of the biopsy specimens at the thickest points of each colorectal specimen. Each measurement was carried out by two pathologists independently, using haematoxylin and eosin slides (and trichrome stain if needed) and a calibrated eye piece graticule. When there were capillaries with a thickened wall within the collagen band, band thickness was measured at the part not affected by the capillaries (Fig 1). Interobserver variation was almost exclusively due to different points of the specimens being measured rather than to techniques of measurement. Agreement was obtained after verifying which points were appropriate for measurement. The mean thickness of the collagen band was calculated from both readings at each site in the large bowel, which was divided into caecum, ascending colon to hepatic flexure, transverse colon to splenic flexure, descending colon, sigmoid colon, and rectum. Multiple specimens (up to four) taken from the same site were analysed collectively as a single specimen using a mean collagen band thickness which was evaluated as an average of all specimens at this site. To compare flexible sigmoidoscopic specimens with full colonoscopic specimens, the large bowel was divided into the left colorectum including the rectum to the descending colon and the proximal colon including the splenic flexure to the caecum. The normal collagen band is less than 7 itm thick,58 1118 19 and in reported cases of collagenous colitis the collagen band is thicker than 10 jim and accompanied by mucosal inflammation.258 14 1619 On the basis of these data, we used a mean thickness of 10 jtm or more and an 65 group.bmj.com on June 22, 2017 Published by http://gut.bmj.com/ Downloaded from