Introduction to inflammatory conditions of the small and large bowel

CHAPTER 16 Introduction to inflammatory conditions of the small and large bowel






Inflammatory bowel disease


The term inflammatory bowel disease (IBD) is the umbrella term for ulcerative colitis and Crohn’s disease, which are discrete inflammatory conditions of the gut that share many common features.


Ulcerative colitis, the slightly more common of the two conditions, causes inflammation of the colon, whereas Crohn’s disease can affect any part of the gastrointestinal tract from the mouth through to the anus. Both conditions tend to follow a chronic relapsing and remitting course and can lead to disabling symptoms and complications.


Studies have shown similar rates of IBD in Europe and North America where the estimated incidence of ulcerative colitis ranges from 8.8 to 13.4 new cases per 100 000 population per year, with slightly lower rates for Crohn’s disease of 5.6 to 8.6/100 000/year. The incidence of Crohn’s disease appears to be increasing, while that of ulcerative colitis is stable (Loftus et al., 2007). Rates of IBD in Africa and Asia are thought to be much lower, although limitations in case definition may have led to some underestimation. All age groups can be affected, although the condition is unusual in infancy, with the peak age of diagnosis occurring between the ages of 15 and 30 years, with a second peak between the ages of 50 and 80. Women and men are affected equally (Gunesh et al., 2008).






Microbial factors


As with environmental factors, most of the early work in this field focused on trying to identify ‘the’ infective cause of IBD. Potential candidates included Mycobacterium paratuberculosis, which is known to cause a Crohn’s-like illness in cattle called Johne’s disease. However, this has always been controversial and, to date, no clear cause has been identified, despite large amounts of research, although it remains possible that M. paratuberculosis may play some part in the IBD story (Freeman and Noble, 2005). Other equally controversial studies have focused on the measles virus and the potential link between measles vaccine and Crohn’s disease (Thompson et al., 1995) but, once again, this association has not been confirmed. Consequently, recent research has tended to move away from looking at specific organisms and has focused on the interaction between the gut and the microflora of bacteria it contains. This shows potential as an area for research, although, like the field of genetics, the area is hugely complex; for example, it has now been shown that IBD patients are more likely to have received antibiotics in childhood (Hildebrand et al., 2008), which is just one of the many factors that could have an impact on gut flora.



Signs and symptoms


The signs and symptoms of inflammatory bowel disease largely depend on the site affected and the nature of bowel involvement at the site. Consequently, the symptoms of ulcerative colitis, which only involves the colon, are more predictable than those of Crohn’s disease, which can occur anywhere within the gastrointestinal (GI) tract (Figure 16.1). However, a number of patterns can be recognized. In addition, both ulcerative colitis and Crohn’s disease can be associated with a number of symptoms that occur outside of the GI tract (Table 16.2), particularly when the disease involves the colon (Orchard, 2003).





Ulcerative colitis


Ulcerative colitis (UC) causes superficial inflammation of the colon, so the major symptoms are those of bowel upset in the form of diarrhea, urgency to pass stool and the passage of blood-stained stools. Unlike Crohn’s disease, fistula formation and bowel strictures are relatively uncommon and the lack of deep inflammation means that pain is not usually a significant symptom.


The relapsing and remitting nature of UC means patients experience symptoms at times when the disease is active, commonly referred to as a flare, interspersed by periods without symptoms. Symptoms tend to build up gradually and often last for several weeks at a time. The severity of symptoms is at least in part explained by the extent of colon affected. The rectum is inflamed in all patients, but the extent of proximal colonic inflammation varies, with approximately 30% of sufferers having disease confined to the rectum, 40% with disease of the left colon and 30% developing total colonic inflammation (Jess et al., 2006). Individuals tend to follow the same pattern with each flare leading to inflammation in the same part of the colon, with only around 15% of patients experiencing extent progression over time.


Most patients with proctitis and left-sided colitis present with relatively mild or moderate symptoms with little or no systemic upset and are managed as outpatients, whereas patients with pan colonic involvement (Figure 16.2

Dec 26, 2015 | Posted by in GASTROINTESTINAL IMAGING | Comments Off on Introduction to inflammatory conditions of the small and large bowel
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