OBJECTIVE Abdominal palpation with Ou MC manipulation (APOM) has showed to be more sensitive than bimanual pelvic examination for the diagnosis of pelvic inflammatory disease in women with acute abdomen (JEM. 2010;). This study compared APOM with traditional abdominal palpation (AP) for diagnostic reliability and enquired into the mechanism of APOM. METHODS From January 2006 through December 2009, 113 women with acute abdomen attending an emergency department received AP and APOM. Of the 113 women, 91 had pelvic organ disease, whereas 21 had nonpelvic organ disease and 1 had pelvic and nonpelvic organ disease concurrently. RESULTS Excluding the case with concurrent pelvic and nonpelvic organ disease, the sensitivity of APOM for the diagnosis of pelvic organ disease was significantly greater than that of AP (P=.003). Abdominal palpation with Ou MC manipulation also showed greater specificity of excluding pelvic organ disease than did AP (P=.003). Overall, 37.2% of patients with muscle guarding had repeated APOM or APOMs with aggravated isolation, which made the location of the diseased organ more distinct to identify. CONCLUSIONS The delimitation by APOM as a separation zone may allow positional recognition of the tenderness with decreased overlap of signs. However, in cases with muscle guarding, initial APOM might not be able to locate tenderness effectively until repeated APOM or APOMs with aggravated isolation lead to extensive space shielding and isolation of visceral organs. This implies that tenderness location by APOM may also relate to space shielding and pelvic organ isolation.