The Clinical Implications of Overlap Between Constipation and Common Functional Gastrointestinal Disorders.

Functional gastrointestinal disorders (FGIDs) are classified and categorized by the Rome criteria based on patients’ symptoms, but some FGIDs have common pathophysiologic mechanisms, such as visceral hypersensitivity, dysmotility, altered interactions of gut and brain, dysregulated mucosal immunity, and so on. Probably because of these shared pathophysiologic mechanisms, patients with one FGID may also have other FGIDs, or complain of the corresponding symptoms. Such overlap of FGIDs has been reported between functional dyspepsia (FD), gastroesophageal reflux disease (GERD), and irritable bowel syndrome (IBS).1 Also, non-gastrointestinal (GI) diseases, including functional somatic syndromes such as fibromyalgia and overactive bladder syndrome, can overlap with FGIDs. The most frequent overlap has been reported between FD and IBS: studies have shown that 32% of patients with FD also have IBS, and up to 37% of IBS patients also have FD.2,3 A Korean study has also reported an approximately 50% overlap between FD and IBS.4

However, whether constipation overlaps with common FGIDs such as FD and GERD has been infrequently investigated. In this edition of the Journal of Neurogastroenterology and Motility, the authors publish a prospective, nationwide multicenter study using validated questionnaires including quality of life (QOL).5 In their study, the authors report the prevalence of overlap between constipation and FD or GERD, risk factors for such overlap, and the influence of overlap on QOL. Of the 759 study subjects with constipation enrolled from 19 centers (59.4% of functional constipation and 40.6% of constipation-predominant IBS [IBS-C]) 17.9% also had GERD, 10.5% had FD, and 6.7% had both GERD and FD. On the other hand, 492 (64.8%) of the 759 subjects did not have GERD or FD. Overlap with GERD or FD was more frequent in those with IBS-C than in those with functional constipation. The authors also show that overlap was associated with such factors as laxatives use, low intake of fiber, pulmonary diseases, and herniated nucleus pulposus. Constipated patients with overlaps with other FGIDs also showed more severe symptoms, and constipation-associated or general QOL was poorer than those without. Although the authors did not subdivide FD and GERD-dividing FD into epigastric pain syndrome and postprandial distress syndrome, and GERD into erosive esophagitis, non-erosive reflux disease, reflux hypersensitivity, and functional heartburn, a previous study has reported that postprandial distress syndrome patients frequently suffer from IBS-C.6

The question whether the various manifestations of constipated patients define a single disease entity, or rather are shared symptoms of two or more types of FGID, has not been clearly answered. Regardless, in managing patients with constipation, and with other common FGIDs as well, overlap syndromes between constipation and GERD or FD should be recognized and considered. As shown by this study, patients with overlap syndromes tend to complain of severer symptoms7 as well as psychological comorbidities8 and poorer QOL.9 Although there is no consensus on the optimal management of patients with overlap syndromes, appropriate medications, such as motility modulators and pain modulators, should be selected.10,11 Importantly, management of patients with such overlaps should also be focused on psychological factors influencing QOL, because their responses to general treatments are likely to be poorer than those of patients with constipation alone.