Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) share some demographics and symptomatology. At least 40% of IBD sufferers in apparent clinical remission will present at some time with IBS symptoms, usually those of IBS-diarrhea. A 2017 Dutch study of 74 IBD patients with inactive disease by fecal calprotectin levels, for instance, reported that 45% suffered IBS-like episodes.”The prevalence of IBS-type symptoms in IBD patients in biochemical remission is high,” Daniël Hoekman and associates wrote. “A significant proportion of IBS-type symptoms is unrelated to ongoing inflammation and probably reflects true IBS.”
Such “overlap” patients pose diagnostic and therapeutic dilemmas because of the overtly normal calprotectin, a surrogate marker of inflammation. That suggests that subclinical inflammation and lingering inflammation-induced visceral hypersensitivity may be driving IBD symptoms – or not. “The main thing is to get the diagnosis right,” Eamonn Quigley, MD, of Houston Methodist Hospital, told MedPage Today.
Is the persistent pain perhaps due to the overestimation of remission by current tests? he asked. “Are the symptoms really about IBS, or are they about very low-grade IBD that we can’t pick up? We don’t want to undertreat IBD patients who still have ongoing inflammation, but neither do we want to overtreat those who just have IBS.”
Quigley noted that the percentage of doubly affected patients in apparent remission used to be considerably higher, since initial studies were done before calprotectin testing was widely available and remission was determined by colonoscopy and blood work alone.
Some researchers have postulated that these increasingly prevalent and sometimes overlapping GI conditions share common origins and could even represent opposite ends on the spectrum of a single disease entity. But more recent research suggests that, overlap notwithstanding, the evolution of IBS is quite separate from that of IBD. A 2017 global study by Andrew Szilagyi and Xiaoqing Xue looked at IBD-associated geographic markers and compared them with IBS in an attempt to evaluate evolutionary links between the two as well as the possibility that IBS is an IBD precursor. The results showed no correlations for IBS with IBD-linked factors such as lactase distribution, sunshine exposure, and latitude.
The researchers concluded that the two conditions do not follow similar global geographic patterns of development: “Similarities [of IBS] with IBD may result from subgroups (not yet identified) within the current Rome criteria of IBS. Alternatively, limited intestinal gut-brain responses to host microbial interactions may result in similar overlap features in both.”
Regarding the profile of doubly affected patients, Manreet Kaur, MD, of Baylor College of Medicine in Houston, told MedPage Today that IBD patients with IBS symptoms are more likely to have Crohn’s disease, long-standing disease, and some kind of psychosocial comorbidity such as depression, anxiety, and maladaptive coping methods. A history of severe IBD also makes IBS symptoms more likely in IBD patients.
Added Quigley: “We also find that more of our IBD-IBS patients are smokers.”
In the absence of randomized clinical trials — which are urgently needed, Quigley stressed — evaluation should begin with measuring fecal calprotectin.
If this marker lies clearly in the range of active inflammation, then further assessments of IBD activity and appropriate anti-inflammatory therapy are called for. If it falls within the normal or a grey zone, symptomatic therapy based on dominant symptomatology and current best practices for IBS should be started.
Although trial evidence is lacking, IBS symptoms in IBD patients respond well to the same therapies used for IBS alone. Among effective treatments is a diet low in fermentable oligo-, di- & monosaccharides and polyols (FODMAP), as Shanti Eswaran, MD, of the University of Michigan in Ann Arbor, recently suggested.
“If the symptoms are out of proportion to the degree of inflammation and there are psychosocial risk factors or clear stress-induced worsening of symptoms and not a lot of objective evidence of inflammation, then a low-dose tricyclic antidepressant may also help,” said Kaur.
She said she would like to see a high-quality clinical study of patients with an established diagnosis of IBD and no ongoing inflammation but who are in discomfort: “These patients should be not just in clinical remission but should have objective radiographic and endoscopic evidence of remission. It would be incredibly informative to see what happens to their symptoms when they’re placed on treatments that would normally be used for IBS alone.”
In Quigley’s view, a prospective study is needed to look carefully at the development of inflammatory markers in individual patients and their microbiomes.
In the meantime, lacking trial data and clear-cut guidelines, physicians must approach these patients experientially. “You have to rely on experience, assessment, and clinical acumen when you feel the symptoms don’t match the degree of inflammation,” Kaur said. “You have to rely on the art of medicine.”