Subclinical intestinal mucosal inflammation in diarrhoea predominant irritable bowel syndrome in a tropical setting

Abstract

OBJECTIVES: There has been increasing evidence to support an inflammatory pathology in irritable bowel syndrome (IBS), especially diarrhoea predominant type (IBS-D).The aim of this study was to investigate for evidence of intestinal mucosal inflammation in IBS-D in a tropical setting. METHODS: In a prospective study over one year, we investigated 49 patients with IBS-D [median age 34 years (range 18-59; M: F 36:13], based on Rome III criteria and 14 controls [median age 46.5 years (range 23-56); M: F 6:8]. None had alarm symptoms, were on NSAIDS or PPIs. All patients had normal ESR, CRP, TSH and stools reports. Stools of all subjects were tested for calprotectin. During colonoscopy, serial biopsies were obtained.Tissue expression of IL-8 and IL-10 were assessed in biopsy specimens using semi-quantitative RT-PCR. RESULTS: Colono-ileoscopy was macroscopically normal and faecal calprotectin was undetectable in cases and controls. Microscopic colitis not otherwise specified (MNOS) was seen in 10/49 cases and 1/14 controls (p=0.43, Fisher's Exact test). A history suggestive of an episode of infectious diarrhoea (ID) was seen in 16/49 cases and 0/14 controls (p=0.013). Tissue expression of IL-8 was significantly higher and IL-10 significantly lower in cases compared to controls (target/standard cDNA ratio, median (range) IL-8: 1.25 (0.75-2) vs 0.85 (0.63-1.37), p<0.0001, Mann-Whitney U test; IL-10: 0.33 (0-0.63) vs 0.55 (0.5-0.7), p<0.0001). There was a significant inverse correlation between IL-8 and IL-10 expression (Pearson Correlation, (-) 0.509; p<0.01). CONCLUSIONS: There is evidence for sub-clinical intestinal mucosal inflammation in patients with IBS-D in a tropical setting, whether a history of ID or MNOS was present or absent.