A new look at irritable bowel syndrome and a proposed treatment plan.

Irritable bowel syndrome (IBS) is a chronic and episodic illness characterized by altered bowel habits and associated abdominal pain. Considered a functional disease caused by abnormal motility of the gut and abnormal pain perception, traditional treatments aimed at relieving the symptoms of altered bowel habits with bulk forming additives, antidiarrheal medicines, and laxatives have been largely unsuccessful. This study proposes an individualized treatment plan based on the known physiology of gut motility, recognized neurotransmitters of pain perception, and associated psychiatric profiles of constipation- and diarrhea-predominant IBS patients. In our clinical practice, patients with constipation-predominant IBS display a psychiatric profile consistent with anterior cingulate gyrus hyperactivity (overfocus and cognitive inflexibility). Anterior cingulate gyrus overactivity causes water retention and decreased gut motility leading to constipation, but is ameliorated by selective serotonin reuptake inhibitors. In contrast, patients with diarrhea-predominant IBS display a psychiatric profile consistent with overactivity of the limbic system of the brain (excessive worry and depression) including the hypothalamus where initiation of the autonomic nervous system takes place. Tricyclic antidepressants suppress the firing of autonomic nervous impulses from the hypothalamus, lessening diarrhea and promoting GI tract stability. Pain from the GI tract is mediated through the autonomic nervous system which contains GABA receptors (the primary inhibitory neurotransmitter of the brain). For this reason GABA-mimic drugs such as Gabapentin can mute pain perception in IBS patients. Some IBS patients demonstrate increased immune response through mast cell proliferation in the small bowel which can be suppressed by appropriate anti-inflammatory agents. Currently, new IBS patients and IBS patients refractory to other treatment regimens have been started on the new proposed treatment plan. Their progress will be reported in turns of symptom relief and satisfaction with medical therapy.

Carol A. Leitner, MD, FACS, J.A. Dias, and Keith L. Roberts. University of Alabama, Birmingham, AL.