Mast cells are increased in the small intestinal mucosa of patients with irritable bowel syndrome: A systematic review and meta‐analysis

BACKGROUND: Colonic mast cells have been proposed to be related to the pathophysiology of irritable bowel syndrome (IBS). Whether mast cell counts are altered in the small intestine, a less-explored region in patients with IBS is not completely clear. METHODS: PubMed and EMBASE were searched for case-control studies on mast cell count/density in the small intestine of patients with IBS vs controls through February 2019. Mast cell counts were separately analyzed in the duodenum, jejunum, and ileum. Data were pooled using the standardized mean difference (SMD) method. When zero was not within the 95% confidence interval (CI), the SMD was considered significant. KEY RESULTS: Data from 344 patients with IBS and 229 healthy controls from three studies in the duodenum, six in the jejunum, and five in the ileum were pooled in this meta-analysis. The number of mast cells was significantly higher in the ileum (SMD: 1.78 [95% CI: 0.89, 2.66]) of patients with IBS. Mast cell counts were not significantly different in the duodenum (SMD: 0.81 [-0.06, 1.67]) or the jejunum (SMD: 0.58 [-0.03, 1.19]) of patients with IBS vs healthy controls. CONCLUSIONS AND INFERENCES: Mast cells are increased in the small intestine of IBS vs controls, mainly in the ileum. Future studies should address whether such findings are IBS subtype or gender-dependent. Methodological variations, single-center bias, and the limited number of studies included in this meta-analysis may affect the final results.