Introduction Painful symptomatic diverticular disease (SDD) is a common but poorly understood condition. Approximately 20% of patients with diverticulosis complain of pain, but there are currently no effective treatments. We have previously reported peripheral immune activation and alteration in colonic nerve function in SDD.

Aims To test the significance of this immune activation by performing the first parallel design, double blind, randomised placebo controlled trial of an anti-inflammatory drug, mesalazine in SDD.

Methods Patients with confirmed SDD underwent an unprepared flexible sigmoidoscopy and biopsies at baseline and after 12 weeks treatment, completing diaries of pain and bowel habit. They were randomised to receive 3 g per day of mesalazine (M) or identical placebo (P) for 12 weeks with follow-up visits at 2 & 4 weeks. RNA from sigmoid biopsies was analysed using a custom made gene card. Gene expression and changes in symptoms were assessed between baseline and final visits using Wilcoxon signed-rank test.

Results 43 volunteers were recruited (F:M; 24:19), but 11 withdrew during the study resulting in 18 and 14 participants in the P and M groups respectively. M significantly reduced important inflammatory and pain genes including those involved in response to bacterial ligands (Abstract OC-119 table 1), changes not seen with P. M but not P significantly reduced the duration of abdominal pain (Median (range) (hrs/day) P group Pre 1.0 (0–5), Post 0.65 (0–4) p0.1919; M Group Pre 3.0 (0–20), Post 0.125 (0–5.5) p0.0413).

Conclusion This pilot study suggests that mesalazine significantly alters many of the pathways mediating immune activation by bacteria thought to contribute to pain in SDD and may provide benefit for patients. However further larger studies are required to confirm these mechanisms and efficacy of mesalazine in this group.

Competing interests J Smith grant/research support from: Wellcome Trust Training Fellowship, Conflict with: £17 000 Gift from Dr Falk Pharma for manufacture of medication for the study, D Humes: None declared, K Garsed: None declared, C Lam: None declared, A Zaitoun: None declared, A Bennett: None declared, J Scholefield: None declared, R Spiller: None declared.