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P290. Diagnosing microscopic colitis - is colonoscopy necessary?

T. Chapman1, A. Pennefather1, G. MacFaul1, A. Abraham2, 1Milton Keynes NHS Foundation Trust, Gastroenterology, Milton Keynes, United Kingdom, 2Milton Keynes Hospital NHS Foundation Trust, Histopathology, Milton Keynes, United Kingdom

Background

Microscopic colitis is a common cause of chronic diarrhoea, particularly in older people, and the incidence is increasing. As the endoscopic appearance is typically normal, diagnosis of the two subtypes, collagenous and lymphocytic colitis, relies upon specific histology findings. When suspected, guidelines advise colonoscopy with full biopsy series due to reports of a patchy disease distribution, with false negative rates of up to 40% reported with flexible sigmoidoscopy [1,2]. However, more recent data has challenged this assumption, leaving considerable uncertainty [3]. We report one of the largest consecutive case series to date, examining whether left sided biopsies alone, that could be taken at flexible sigmoidoscopy, are sufficient for the diagnosis of microscopic colitis.

Methods

A retrospective review of all cases of microscopic colitis diagnosed at colonoscopy over a 12-year period (2001–2013) at our hospital was performed. Only colonoscopies with both right (proximal to splenic flexure) and left sided colonic biopsies were included. The diagnostic criteria for microscopic colitis were lymphocytic infiltration in the lamina propria and either ≥20 intraepithelial lymphocytes per 100 epithelial cells (lymphocytic colitis) or a collagenous layer >10 µm (collagenous colitis). The primary aim was to assess the proportion of patients in which microscopic colitis could be diagnosed on left sided biopsies alone.

Results

84 patients were included in the study. 58 (69.0%) were female with a mean age of 59.0 years (SD ±14.7). 44 (52.4%) had collagenous colitis and 40 (47.6%) lymphocytic colitis. 76 (90.5%) had features of microscopic colitis on both right and left sided biopsies, 7 (8.3%) on right side only and 1 (1.2%) on left side only. Hence a diagnosis of microsopic colitis could be made in 77 (91.7%) on left sided biopsies alone. Age, sex and histopathological subtype did not significantly alter the sensitivity of left sided biopsies.

Table: Patient characteristics
DiagnosisCollagenous colitisLymphocytic colitis
n4440
Mean±SD age, yrs59.2±14.658.9±15.0
Female3622
Left sided biopsies diagnostic for microscopic colitis4136

Conclusion

Flexible sigmoidoscopy would have correctly diagnosed microscopic colitis in a high proportion of patients (92%). Given that flexible sigmoidoscopy is less expensive, better tolerated, and can be combined with CT colonography to exclude a proximal malignancy, this has potential implications for the investigation of non-bloody diarrhoea.

1. Fernandez-Banares F et al, (1999), Incidence of collagenous and lymphocytic colitis: a 5-year population-based study., Am J Gastroenterol, 94: 418–23.

2. Offner FA et al, (1999), Collagenous colitis: a study of the distribution of morphological abnormalities and their histological detection, Hum Pathol, 30: 451–7.

3. Bjornbak C et al, (2011), Microscopic colitis: clinical findings, topography and persistence of histopathological subgroups, Aliment Pharmacol Ther, 34: 1225–34.