A 24-year-old woman has a dull aching pain in the umbilical region, and flexion of the hip against resistance (psoas test) causes a sharp pain in the right lower abdominal quadrant. Which of the following structures is most likely inflamed to cause the pain?

The appendix is the most likely structure that is inflamed. It lies in the right lower quadrant, and of the choices provided, it is most closely associated with the umbilical region by way of referral of pain. The patient also exhibited a positive psoas sign when flexion of the hip against resistance was attempted. This is because the iliopsoas muscle group lies directly beneath the appendix, and upon flexion of this muscle group, contact and direct irritation to the appendix can occur. The bladder lies inferior to the umbilicus within the pelvis and is not related to the site of pain or with a positive psoas sign. The gallbladder lies inferior to the liver and is positioned in the upper right abdominal quadrant, which is superior to the umbilicus. It is not associated with a positive psoas sign. The pancreas lies behind the stomach and is positioned between the spleen and the duodenum. It therefore lies in the upper left quadrant and is superior to the umbilicus. The uterus is located within the pelvis and is positioned anteflexed and anteverted over the bladder. It lies inferior and medial to the iliopsoas group and would not be affected by flexion of these muscles.