What is referred pain in acute abdomen?

Pain distant from site of affected organ. E.g. patient feels pain from his cardiac infarct in his abdomen; other thoracic pain etiologies: pneumonia, pleurisy, pleural effusion, all could cause abdominal pain. ● Distorted central perception of the site of pain due to confluence of afferent fibers from disparate areas in the posterior horn of the spinal cord. ● Pain starts as a vague visceral pain and later on becomes more localized. That is due to the inflammation reaching the parietal peritoneum; the patient then becomes more able to pin-point the site of the organ. E.g. In appendicitis, pain starts as peri-umbilical or epigastric when it is still visceral, and later on becomes more localized at the right iliac fossa at McBurney’s point due to irritation of the parietal peritoneum at that level.