This anomaly occurs because the pain nerves deep in the intestines do not localize well to an exact spot on the abdominal wall, unlike pain nerves in muscles. Pain from a stomach ulcer or gallstone can be interpreted by the brain as pain from the stomach, liver, gall bladder, duodenum, or first part of the small intestine. It will "refer" pain often to the mid upper abdomen, the epigastrum. Because the appendix is a piece of intestine, it follows a similar referral pattern. An appendix with some early inflammation may give a non-specific irritation somewhere near the umbilicus. Should the inflammation become severe, it may actually irritate the inner lining of the abdominal cavity called the peritoneum. This thin layer of tissue lies deep to the abdominal wall muscles. Now the pain has become "localized". If pressure is applied to the muscles of the right lower abdomen near a very irritated appendix, then the muscle fibers in that area will be stretched and will hurt.
Process
Pathologic explanation: This maneuver elicits tenderness in the right lower abdomen, because contents of the left lower abdomen are shifted upon application of pressure, further irritating the inflamed peritoneum. A Rovsing's sign is elicited by pushing on the abdomen far away from the appendix in the left lower quadrant. The appendix, in a large majority of people, is located in the right lower quadrant. While this maneuver stretches the entire peritoneal lining, it only causes pain in any location where the peritoneum is irritating the muscle. In the case of appendicitis, the pain is felt in the right lower quadrant despite pressure being placed elsewhere. Most practitioners push on the left lower quadrant to see where the patient complains of pain. If pain is felt in the right lower quadrant, then there may be an inflamed organ or piece of tissue in the right lower quadrant. The appendix is generally the prime suspect, although other pathology can also give a "positive" Rovsing's sign. If left lower quadrant pressure by the examiner leads only to left-sided pain or pain on both the left and right sides, then there may be some other pathologicetiology. This may include causes relating to the bladder, uterus, ascending colon, fallopian tubes, ovaries, or other structures. The eponym Rovsing sign is also used in patients with horseshoe kidney, consisting ofabdominal pain, nausea, and vomiting with hyperextension of the spine. While Rovsing's test is frequently performed in suspicion of appendicitis, its sensitivity and specificity have not been adequately evaluated, and is considered by some to be an antiquated examination test.