Referred Pain A Key Characteristic of Visceral Pain
A patient with "pure" visceral pain is seldom seen in the clinic, as this phase usually lasts only a few hours. Instead, most clinically significant forms of visceral pain are referred to somatic areas. Although the physiological basis for referred pain is incompletely understood, it is generally believed to result from the fact that nerve signals from several areas of the body may "feed" the same nerve pathway leading to the spinal cord and brain. Visceral pain by itself is typically felt in the mid-line in the Abdominal Wall" href="/abdominal-wall/superficial-circumflex-iliac-artery.html">epigastric, peri-umblical or hypogastric regions, reflecting the ontogenic origin of the involved organ from the fore- mid- or hind-gut respectively and is perceived as a deep and dull discomfort instead. Referred pain, which sets in soon after and comes to dominate the clinical picture, is perceived in overlying or remote superficial somatic structures such as skin or abdominal wall muscle, with the site varying according to the involved visceral organ. Further, referred pain is now sharper and assumes several of the characteristics of pain of somatic origin and indeed may dominate or even mask any underlying visceral pain.
If carefully questioned, many patients with chronic abdominal pain of visceral origin will indeed describe two types of pain, not always occurring simultaneously. However, physicians often make the mistake of lumping these together into a single pain; the result is that the disparate descriptions (eg, one diffuse and dull, the other localized and sharp) are now perceived as paradoxical and serve to reinforce the perception that the complaints are not "organic" in nature. Referred pain is therefore more helpful in determining the site of the underlying disorder than the original pure visceral pain, which tends to be perceived in the midline regardless of the organ involved.
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