Irritable Bowel Syndrome

IBS is defined by the Rome II criteria as a functional bowel disorder in which there is the presence of continuous or recurrent abdominal pain or discomfort that is relieved with defecation or associated with a change in bowel habit (2). IBS is a common disease afflicting approximately 10% of the population (1,3-6). IBS patients report reduced quality of life (5,7), with several extraintestinal symptoms (5). Estimates of the total cost of IBS per annum in the United States is $25 billion through direct costs of health-care use and indirect costs of absenteeism from work (1).

IBS can be subclassified into three groups based on altered bowel habit: constipation predominant, diarrhea-predominant, and alternating (5,8-11). Another subclass has now been added, postinfectious IBS (12). However, despite this heterogeneous population of patients, enhanced colonic mechanosensation is a hallmark of all subtypes of IBS and as such increased perception of mechanical distension of the distal colon/rectum has become the best-characterized clinical manifestation of IBS (1,13,14). The extent of this enhanced colonic sensation is considerable, as a colorectal distending volume of approximately 60 mL evokes pain in less than 10% of normal subjects compared with greater than 50% of IBS patients. Therefore there is leftward shift in the psychophysical function of IBS patients suggesting the presence of hyperalgesia in IBS (13). There is a general agreement that this visceral hyper-sensitivity and hyperalgesia correlates well with the overall severity of the disease (1,15), which is significant as pain is the symptom that affects quality of life the most (7).

There are various mechanisms, which are thought to be involved in the visceral hyper-sensitivity experienced by IBS patients; however, there is no clear consensus, which may reflect the heterogeneity of the disease. The hypothesized mechanisms include sensitization of the extrinsic sensory afferent endings within the gut wall, hyperexcitability of dorsal horn neurons, and modulation of the brain responses to information signalled by the gut. Recent evidence from behavioral and functional imaging studies of patients with IBS suggests that changes occur at the level of the primary afferent neuron and/or spinal cord but not in higher cortical centers (16,17), thereby supporting the notion that peripheral mechanosensation plays an important role in the etiology of this disease. In particular, there is circumstantial evidence suggesting that hypersensitivity of lumbar splanchnic afferents induces hyperalgesia in IBS patients (16,18). Consistent with the role of peripheral mechanisms, subsets of IBS patients have increased numbers of inflammatory cells in the colonic mucosa (19), while activated mast cells have been found in close proximity to colonic nerves, which correlate with abdominal pain in IBS patients (15), suggesting that activation or sensitization of extrinsic sensory endings within the gut wall may play a key role in IBS. Recent hypotheses support this notion by suggesting a low-grade inflammatory response at the level of the gut wall could be involved (12,15).

By contrast, postinfectious IBS patients appear to have a clearer etiology as they describe an acute onset of symptoms (as classified by Rome II criteria) after a gastroenteritis episode but previously have entirely normal bowel habit (12,20). For patients who had experienced gastroenteritis, the relative risk of developing IBS within the following year was approximately 11 times greater (12). These patients typically have diarrhea-predominant IBS and account for 6% to 17% of the IBS population (11). A role for stress in the pathophysiology of IBS has also been suggested, with psychological and environmental stressors associated with onset and symptom exacerbation, possibly via central mechanisms or via activation of sensitized immune cells within the gut wall (5,6,20-26).

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Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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