Authors: Premysl Bercik, MD*, Elena F. Verdu, MD, PhD, Stephen M. Collins, MD, FRCP

Institution: Intestinal Disease Research Program and Division of Gastroenterology, McMaster University, 1200 Main Street West, HSC 3N49C, Hamilton, Ontario L8N 3Z5, Canada.

Summary: The authors believe that inflamed bowel disease and at least a subset of irritable bowel syndrome patients exist at two ends of the same spectrum of pathophysiology, which involves immune activation and inflammation.

This is prompted by the observation that IBS symptoms may precede IBD, which reflects gut dysfunction generated by subclinical inflammation. It also has been observed that IBS occurs in patients in remission from IBD. This concept is underpinned by results of basic scientific studies in animal models showing that immune activation and inflammation restricted to the mucosal compartment result in profound changes in neuromuscular function that may persist after recovery of the mucosa.

Emerging evidence shows similarities in genotype between IBD and a subset of IBS patients; polymorphisms of genes that encode cytokine secretion may result in an imbalance of pro- and counter inflammatory signals. This in turn would lead to inefficient down-regulation of inflammatory responses and promote low-grade inflammation.

It is a matter of the severity of inflammation that separates IBD and this IBS subset, and this may reflect additional genetic abnormalities or greater exposure to environmental factors in the case of IBD. This prompts the question as to whether IBD is more common in patients with IBS, and there is some evidence to support this.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15862932&dopt=Citation

• Quality of Life in Inflammatory Bowel Disease in Remission: the Impact of IBS-like Symptoms and Associated Psychological Factors
• Identification of a Prodromal Period in Crohn's Disease but not Ulcerative Colitis
• Inflammatory Bowel Disease and Irritable Bowel Syndrome: Separate or Unified?
• Inflammatory Bowel Disease and Irritable Bowel Syndrome