Original articlesReview articleSomatic comorbidities of irritable bowel syndrome: A systematic analysis
Introduction
In irritable bowel syndrome (IBS) patients, somatic (intestinal and extraintestinal) comorbidities, particularly extraintestinal symptoms, are present twice as much as in controls [1]. The appearance of comorbidities in patients with IBS is associated with reduction in quality of life [1] and increased health care seeking, with a consecutive rise in costs. More than 65% of the expenses incurred by IBS patients can be attributed to extraintestinal indications [2]. Moreover, a positive correlation between the appearance of one or more IBS-related somatic comorbid conditions and the severity of IBS symptoms, as well as the occurrence of anxiety and depression, was detected [3], [4]. Vandvik et al. [5] revealed a positive correlation between the incidence of somatic comorbidities and higher levels of mood disorder, health anxiety, neuroticism, adverse life events, reduced quality of life, and increased health care seeking, compared to IBS patients without somatic comorbidities.
Various concepts explaining this phenomenon (e.g., similarities in underlying pathophysiological mechanisms such as visceral hypersensitivity and dysregulation of the autonomic nervous system) have been proposed [6].
Section snippets
Intestinal comorbidities
Besides the considerable overlap between functional gastrointestinal disorders, current data suggest that IBS patients also suffer from various intestinal comorbidities (Fig. 1).
IBS and intestinal comorbidities: key messages
A wide spectrum of diagnostic procedures is necessary to exclude other conditions when IBS is suspected to be the cause of abdominal complaints due to the broad overlap between various gastrointestinal diseases. Furthermore, in the individual patient, dominating symptoms often vary over time, making it even harder to categorize the IBS subtype according to Rome criteria, which is essential for an adequate therapeutic procedure. Besides the characterization of the leading symptoms, it is
Extraintestinal comorbidities
IBS patients, as well as patients with other functional gastrointestinal diseases, remarkably more often suffer from extraintestinal comorbidities than patients with nonfunctional gastrointestinal diseases (Fig. 2). Comparison of epidemiological studies showed a high variance of data. Among others, this can be attributed to different study conditions in primary, secondary, and tertiary care, and different definitions of diseases, as well as diverse classification of patient subgroups.
IBS and extraintestinal comorbidities: key messages
Except for BHR, there is clear evidence that the mentioned extragastrointestinal symptoms are significantly more common in IBS patients than in controls. The best-documented nonpsychiatric extraintestinal comorbidities are fibromyalgia, chronic fatigue syndrome, and chronic pelvic pain. The evidence supporting a common underlying etiology is unconvincing. Common psychological features or physiological mechanisms are possible but have not been proven yet.
The observation that IBS patients
Common pathophysiological mechanisms in IBS and somatic comorbidities
The frequency of intestinal and extraintestinal comorbidities in IBS suggests that the underlying pathophysiological mechanisms are not confined to the respective organ, but rather involve superior systems such as the autonomic nervous system and the brain–gut axis.
Regarding their clinical manifestation, obviously many similarities can be found between IBS and the most frequent somatic comorbidities (FM, chronic fatigue syndrome, chronic pelvic pain, and TMJ). In all of these diseases,
IBS patients with somatic comorbidities: subgroup or part of a global disorder?
Factor analyses proved that IBS occurs independently of FD and other functional gastrointestinal diseases [87], [88], [89]. Moreover, IBS shows a wide overlap with FM, chronic fatigue syndrome, anxiety, and depression, although the single diagnoses are autonomous. This argues against a global disease.
Furthermore, other multivariate statistical analyses also indicated that comorbidities of IBS are independent diseases [57], [90], and there is clear evidence that IBS, FM, and chronic fatigue
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