When the appendix becomes inflamed, the visceral sensory fibers are stimulated and the patient fells extreme pain in the abdomen which is referred to appendicitis.
During this inflamed condition visceral sensory fibers enter the spinal cord with the sympathetic fibers at spinal cord level T10. The pain is referred to the dermatome of T10, which is in the umbilical region.
The pain is diffuse, not focal; every time a peristaltic wave passes through the ileocecal region, the pain recurs. This intermittent type of pain is referred to as colic.