Appendicitis offers a good example of visceral and somatic pain. It also offers an example of referred pain, but this is really just part of the visceral pain.
The patient initially experiences a vague periumbilical discomfort which may be constant or wax and wane. Following this there may be nausea and vomiting particularly if the patient is young. After a variable period the pain becomes more severe and is now felt in the right iliac fossa. This pain is continuous and is aggravated by movement.
The first vague central pain that the patient experiences is due to pain from the appendix itself. The more severe pain localised to the right iliac fossa is due to irritation of the parietal peritoneum adjacent to the appendix.