IBS Fact : Evidence-based management of irritable bowel syndrome

Irritable bowel disease (IBD) vs irritable bowel syndrome (IBS)

Because their names sound a lot alike, it is easy to confuse irritable bowel syndrome with inflammatory bowel disease (commonly called IBD). However these are two different conditions with different underlining pathological mechanisms and treatment strategies. The name IBD encompasses several diseases but its two main forms are Crohn’s disease and ulcerative colitis. Both refer to a long-lasting inflammation of the lining of the digestive tract. In Crohn’s disease, the inflammation affects different areas of the digestive tract, such as the large or small intestine or both, and often spreads deep into affected tissues. Ulcerative colitis is usually limited to the colon and rectum. IBD patients experience symptoms similar to those in IBS. Among these, diarrhoea and anaemia are very common. Others include abdominal pain, fatigue, weight loss, vomiting, constipation, urgency to evacuate, bloating, and passage of mucous and rectal bleeding. Some patients suffer from continuous disease activity while others experience episodes of active disease (flares) of different severity and frequency interspersed with periods of remission. Similar to IBS, the underlying causative mechanisms of IBD are multifactorial and largely unknown. However, in contrast to IBS, IBD is a structural disease, which means that the physical damage causing the symptoms can be clearly identified in most cases. Doctors can pinpoint the inflamed intestinal tissue by endoscopic examination of the intestinal mucosa and by microscopical assessment of collected tissue samples (biopsies). This is a fundamental difference when compared to IBS, which lacks clearly observable structural changes and is therefore referred to as a functional disease (i.e. diagnosis is based on disturbed function). Consequently, endoscopy, X-ray, or biopsies can be used to make a positive diagnosis of IBD while excluding IBS in the majority of patients. Because of the similarity in symptoms, a group of patients with actual IBD might, however, be initially suspected to suffer from IBS. Indeed this seems to be the case for a small fraction of patients, particularly those in a state of temporal remission in which inflammation has subsided and can no longer be observed by endoscopy. According to studies, approximately 1% of patients with a tentative diagnosis of IBS turn out to suffer from IBD. In addition, some data suggests that true IBD patients have a higher risk of developing IBS in the long term compared to the general population. In a study following IBD patients during 15 years, 1.8% of them developed IBS, in contrast to 0.5% in the general population over the same 15 year period. Thus, in a small number of cases, patients with IBD may be diagnosed equivocally with IBS or they may develop IBS in addition to IBD. However, in the large majority of cases, a clear differentiation between IBD and IBS can be readily made by colonoscopy combined with biopsy. Laboratory testing for inflammatory proteins such as calprotein in faeces may also be useful as it allows identification of ongoing inflammation suggesting IBD. Such assays for inflammatory proteins may be particularly useful to diagnose IBD during periods of remission, during which inflammation of the intestinal tract may not yet, or no longer be visible by endoscopy. Red flags that seem to have some predictive value pointing toward IBD are blood in stools and recent antibiotic use. Use of antibiotics seems an unusual factor to predict a condition. It is, however, based on the observation that future IBD patients seem to have a relatively higher use of antibiotics even prior to the diagnosis of their condition. The cause for this association has not been identified. Some studies suggest that frequent use of antibiotics actually predisposes for development of IBD, particularly in young children, by affecting the intestinal flora and the development of the immune system. Other studies oppose this view and suggest that the frequent use of antibiotics merely reflects the need for treatment of abdominal symptoms caused by IBD even before a definitive diagnosis has been made. Thus, the cause-effect relationship between IBD and antibiotics remains to be clarified. Other red flags that might suggest IBD are fever, weight loss, night-time diarrhoea, and first-degree relatives with IBD. Extra-intestinal symptoms such as inflammation in the skin, joints, or eyes are also common in IBD patients. However, it should be noted that IBD is much less frequent than IBS, and the red flags are certainly not to be considered as hard evidence for one or the other condition.

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