ABDOMINAL PAIN: ORIGIN OF ABDOMINAL PAIN
Pain-sensitive neurons from visceral organs and the peritoneum travel in symptomatic pathways to spinal sensory neurons. The afferent endings are located in the smooth muscles of hollow organs, in organ capsules, in the peritoneum, and in intra-abdominal blood vessels. Abdominal organs are insensitive to stimuli such as cutting, tearing and burning.
Generally, only three processes produce pain in the alimentary tract:
(1) stretching or tension in the wall of a hollow organ or the capsule of a solid organ as a result of forceful muscular contraction, muscle spasms, distention, or traction.
(2) inflammation with associated release of substances, such as bradykinin, prostaglandins, histamine, and serotonin, that stimulate or sensitize nerve endings.
(3) ischemia, which releases noxious tissue metabolites. Spinal sensory neurons also receive input from peripheral non-pain neurons, thus establishing the basis for referred pain to extra-abdominal sites.