The sign describes a firm swish of the examiner’s index and middle finger across the patient’s abdomen from xiphoid sternum to first the left and then the right iliac fossa. A positive Massouh sign is a grimace of the patient upon a right sided (and not left) sweep. The explanation for the reliability of this diagnostic tool is based on the fact that appendicitis in the initial stage usually causes localised irritation of the peritoneum. The well innervated peritoneum is very sensitive to pain and therefore sensitive to jouncing movements. Similarly this is the explanation for other signs of localised peritonitis such as Murphy's sign, Rovsing's sign or Psoas sign.
The Massouh sign became popular among surgeons in the Southwest Region of England as it is practicable and, together with other diagnostic tools, highly correlates with the appearance of acute Appendicitis.