You now know that you have IBS...but what exactly does this mean? Irritable Bowel Syndrome (such a glamorous name, isn't it?) has been under-researched for decades, but that is finally changing. Over the past few years a great deal of new information regarding the brain-gut interaction that results in IBS has evolved, and more discoveries are being made all the time.
First of all, realize that you are not alone. IBS is estimated to affect 15-20% of all Americans, primarily (but certainly not exclusively) women. This is at least 35 million Americans, and half of them have never even seen a physician for their symptoms. Despite this, IBS is still the most-frequently seen illness by gastroenterologists, and is one the top ten diagnoses among all US physicians. It is also, incredibly, the second leading cause of worker absenteeism (behind only the common cold). These are pretty amazing statistics for a disorder that many people have never even heard of.
Interestingly, because IBS is a "functional" disorder, you can't actually be tested for it. Rather, it is determined by a diagnosis of exclusion. This is because there are no structural, inflammatory, biochemical, or infectious abnormalities present in IBS. In other words, when IBS patients are examined by doctors, there is no physical problem to be found. So, are you just imagining your symptoms? No you absolutely are not. A functional disorder simply means that the problem is an altered physiological function (that is, the way your body works), rather than something that has an identifiable origin behind it. In other words, while an IBS attack and its resulting symptoms are clearly visible as physical manifestations, the underlying cause behind these symptoms is not. The root of the problem in IBS sufferers cannot yet be identified by yielding a positive result from any existing medical tests. What then, precisely, is wrong with the way your body works if you have IBS? Get ready...
The Brain-Gut Interaction
It can be difficult (and until recently, it was downright impossible) to find explicit scientific explanations for the precise bodily mechanisms behind IBS. Because this information is still limited in its availability, and because many people with IBS are given cursory explanations of the disorder without also being handed resources permitting more in-depth research, I'm including a full technical discussion of IBS physiology. If this is beyond the pale for you, please feel free to skip ahead to the next page and the plain-English translation. Otherwise, get ready...
The most recent evaluation model for IBS patients states that the symptoms of the disorder result from the neurologic innervation of the gastrointestinal tract, associated with altered interpretation of neurologic messages from the GI tract by the central nervous system. Input to the central nervous system from the gastrointestinal tract arrives at several different parts of the brain which are associated with interpretation and modulation of pain perception. Neurologic output from these areas are then returned to the gastrointestinal tract via the spinal cord. This circuit (from gut to brain and brain to gut) appears to be abnormal in patients with Irritable Bowel Syndrome, though the exact abnormalities remain unclear.
Visceral (gut) pain in IBS is associated with increased prefrontal cortex activation in the brain. The normal correlation between subjective pain intensity and activation of the anterior cingulate and insula cortices parts of the brain is lost in IBS. Altered visceral perception via changes in reflex responses and viscerosomatic referral areas is common in IBS. Both hyperalgesia (lower pain threshold) and allodynia (pain perceived in non-sensory pathways) are involved in the development of visceral (gut) hypersensitivity. It is believed that, as a result of central sensitization, a sensory memory response is created, which exaggerates and prolongs subsequent stimulation. The pathophysiology of this visceral hyperalgesia (lower pain threshold in the gut) is incompletely understood and appears to be stem from multiple factors. Interestingly, although people with IBS show this visceral hypersensitivity, their peripheral pain thresholds are normal or even elevated in comparison to healthy individuals.
Neuroimaging has actually provided direct evidence of physiological differences between normal individuals and those suffering from IBS in the way a visceral (gut) stimulus is processed in the brain. PET scans show pronounced differences in the activation of certain parts of the brain relating to perception and pain in IBS patients versus normal individuals. MRI scans have demonstrated comparable results.
Okay, in plain English, what does all this mean?
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