Editorial: differentiating chronic idiopathic constipation from constipation-predominant irritable bowel syndrome--possible and important?

Abstract

To the clinician, an attempt to differentiate chronic idiopathic constipation (CIC) from constipation-predominant irritable bowel syndrome (IBS-C) may well represent yet another example of the type of esoteric and clinically irrelevant exercises that aloof academics occupy their time with. Who cares whether the label of CIC or IBS-C is attached to a given patient? Why all the fuss about trying to separate two disorders that are essentially parts of a continuum? While the definition of CIC has evolved from a focus on infrequent bowel movements to that of a more inclusive syndrome which encompasses such symptoms as straining, lumpy or hard stools, a feeling of incomplete evacuation, a sensation of anorectal blockade or obstruction and/or the use of manual or digital manoeuvres to facilitate defaecation, these same Rome III criteria require that there are also ‘insufficient criteria for IBS’.1 Given the centrality of abdominal pain to the definition of IBS,1 its prominence is regarded as the key feature differentiating CIC from IBS-C. Is this really feasible in clinical practice? Where does the abdominal discomfort so frequently reported in CIC become the pain that defines IBS? Recent observations illustrate the challenges posed by attempts to separate CIC from IBS-C.2-5 In one study, no differences in baseline symptoms, bowel habits, oro-caecal or colonic transit were evident between CIC and IBS-C; prominent post-prandial symptoms, alone, differentiated IBS-C.2 Others reported similar demographics and quality of life among their CC and IBS-C populations and found that CIC symptoms, not pain, helped to differentiate, with CIC subjects reporting more straining, and those with IBS-C more incomplete evacuation.3 More damning still was the observation that 89.5% of IBS-C subjects met Rome III criteria for CIC and, conversely, 43.8% of CIC, criteria for IBS-C. That these definitions are unstable was illustrated by the longitudinal component of this study; by 3 months, one-third had switched diagnosis.4 The study reported by Koloski and colleagues now casts further doubt on the wisdom of separating CIC from IBS-C.6 With some exceptions, such as age and participation in exercise, where small differences were observed, individuals with IBS-C and CIC, in the general population, were remarkably similar. Using latent class analysis they went on to identify two clusters, one dominated by CIC and the other comprising equal numbers of CIC and IBS-C. The two groups were largely similar; when it came to symptoms, differences were of severity rather than prevalence, with pain being less severe in CIC, perhaps explaining lower rates of consultation and better scores on the mental functioning component of the quality of life instrument in that disorder. So where does this leave us? Yes there are some differences between IBS-C and CIC but these are far more subtle than current definitions would lead us to believe. Perhaps, it should come as little surprise then that newer therapies introduced for CIC have also proven effective in IBS-C.7 Declaration of personal and funding interests: None.