Small intestinal dysmotility, its role in irritable bowel syndrome and small intestinal bacterial overgrowth: Assessment and management

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders and, for some sufferers, results in significant impairment in quality of life. From the outset, IBS was regarded as a disorder of gastrointestinal motility, and terms such as 'spastic colon' or even 'spastic colitis' applied. As these terms imply, the focus in the early days of the investigation of the pathophysiology of IBS was on the colon and on the left colon, in particular. Subsequently, as advances in manometric technology permitted reliable recordings of motor activity from the small intestine, alterations in small intestinal motility were described in IBS, at rest, following food ingestion and in response to stressful stimuli; some of the abnormal patterns identified seemed to correlate temporally with certain symptoms. More recently, interest in the potential roles of such phenomena as dysbiosis, low-grade inflammation and enhanced intestinal permeability have renewed interest in the potential role of the small intestine and its neuromuscular apparatus in IBS. Relationships between small intestinal dysmotility and small intestinal bacterial overgrowth (SIBO) are more clear-cut given that impaired gut motor activity is one of the primary factors that predisposes to SIBO. Dysmotility is, indeed, the process underlying the development of SIBO in relation to conditions as diverse as scleroderma, diabetes, and intestinal pseudo-obstruction.