Retroperitoneal abscess

The psoas sign, also known as Cope's psoas test or Obraztsova's sign, is a medical sign that indicates irritation to the iliopsoas group of hip flexors in the abdomen, and consequently indicates that the inflamed appendix is retrocaecal in orientation (as the iliopsoas muscle is retroperitoneal). The technique for detecting the psoas sign is carried out on the patient's right leg. [Source: Wikipedia ]