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People with functional gastrointestinal (GI) disorders can have a variety of symptoms that range from painless diarrhea or constipation, to pain associated with diarrhea and/or constipation (usually called irritable bowel syndrome). There is another, less common condition of abdominal pain that is chronic or frequently recurring; it is not associated with changes in bowel pattern or with another medical condition. This condition is called centrally mediated abdominal pain syndrome (CAPS) – formerly known as functional abdominal pain syndrome (FAPS).

CAPS is a functional GI disorder. There are no abnormal x-rays or laboratory findings to explain the pain. It occurs because of altered sensitivity to nerve impulses in the gut and brain, and it is not associated with altered motility in the intestines. CAPS is characterized by continuous or frequent abdominal pain that is often severe. It has little or no relationship to events such as eating, defecation, or menses.

For people with CAPS, the pain can be so all-consuming that it becomes the main focus of their life. Not only does it impact quality of life, but it has a major economic impact as well.

Pathophysiology – Understanding Why People Get CAPS

To understand the basis for chronic abdominal pain syndrome it is helpful to understand how the body experiences pain. Nerve impulses travel from the abdomen to the spinal cord, and then to various areas of the brain.

There are many different areas of the brain involved in the sensation of abdominal pain. One of these connected areas is concerned with the location and intensity of the pain, while another connected area is concerned with memories or emotions. Because of this interconnection, the perception of pain can be affected by emotions or life experiences.

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While symptoms of CAPS can appear without apparent cause, they can also occur after infections or events that stimulate the bowel and also after traumatic life events like the death of a loved one, a divorce, or a history of abuse. During times of added stress, symptoms can worsen.

Repeated injury in the abdomen can cause nerve receptors to become overly sensitive. For instance, if someone has had multiple abdominal surgeries or an infection, a later painful occurrence may be experienced as more painful than previously.

Even normal abdominal activity may be experienced as being painful. It is as if the volume has been turned up on a stereo receiver. This condition is called visceral hypersensitivity (increased sensitivity of the intestines).

Furthermore although the brain has an ability to "turn down" the pain signals from the GI tract with CAPS, this ability is reduced, so even small amounts of intestinal disturbance can be amplified to produce severe pain (central hypersensitivity). So these individuals have an altered "brain-gut axis" where there is a failure of the brain to regulate even normal gut nerve activity leading to increased pain.

Understanding how the brain can modify the pain experience (for better or worse) is essential to beginning any treatment. When someone is feeling anxious or depressed, or focuses attention on the pain, it is experienced as more severe. The use of relaxation training or other techniques can divert attention away from the pain.

If a person has previously had a bad encounter with pain, the fear of having the pain again can actually make the pain worse the next time. If a person takes steps to feel in control of the pain, symptoms will improve. In addition, the amount of support a person receives from family, friends, and other sources can affect how a person responds to pain.

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