Ma. Giamberardino et L. Vecchiet, VISCERAL PAIN, REFERRED HYPERALGESIA AND OUTCOME - NEW CONCEPTS, European journal of anaesthesiology, 12, 1995, pp. 61-66
Visceral pain is a poorly defined, midline sensation but after minutes
or hours becomes 'referred' to a somatic region when it becomes sharp
er and better localized. Referred pain may manifest either with or wit
hout hyperalgesia. Hyperalgesia is more common and can be demonstrated
by changes in pain threshold. This referred hyperalgesia is probably
sustained by central mechanisms, involving a spinal focus facilitating
neuronal signals coming from somatic structures. Once established, th
e central changes may become independent of the peripheral input neces
sary for their initiation. With respect to post-surgical pain associat
ed with operations on the viscus, the main determinant is whether or n
ot the Visceral pathology prior to surgery was algogenic.