Introduction Diarrhoea is a common indication for colonoscopy. International guidelines recommend colonic biopsies should be routinely taken at lower GI endoscopy in patients with diarrhoea [1, 2] to look for microscopic colitis. The epidemiology of contemporary microscopic colitis is largely unknown with published data based on an earlier time period pre-2001 and in small retrospective case series. We have systematically collected a large and contemporary cohort of patients with incident microscopic colitis to help further our understanding of this disease.

Method Colonic biopsies demonstrating microscopic colitis between 2005–2016 were identified from electronic pathology records. GI endoscopy procedures taking place during this time period were identified from an electronic database. Incidence rates were calculated using the total population for Nottinghamshire derived from UK mid-year population estimates [3]. Poisson regression models were used to determine rate ratios.

Results 843 people were diagnosed with microscopic colitis of which 60.7% were female (n=512). The mean age at diagnosis was 65.0 (95%CI 64.0, 65.9) years. 57.5% (n=485) had collagenous colitis and 42.5% had lymphocytic colitis. The incidence rate of microscopic colitis appeared to increase with time (Table). The incidence rate of microscopic colitis in 2016 was twice of that observed in 2009 (incidence rate ratio 1.86; 95% CI 1.41, 2.46). There was a strong, independent graded association between the incidence of microscopic colitis and the number of lower GI endoscopy procedures undertaken (p=0.03).

Conclusion Microscopic colitis diagnosis is becoming more common. It is unclear whether microscopic colitis itself is increasing or greater numbers of lower GI endoscopy are being undertaken causing an ascertainment bias. Further work is required to explore environmental exposures such as drugs associated with microscopic colitis and to observe its natural history.

References

1. . Gut 2003;52:v1-v15

2. . Gut 2016;0:1-7

3. . www.ons.gov.uk

Disclosure of Interest None Declared